Dr. Alex’s latest advice on Covid 19, and a chance to ask questions

August 25, 2020 • 9:00 am

From time to time, my primary care physician Dr. Alex Lickerman posts articles on his website from about what’s going on with the pandemic, concentrating on the scientific research and what it means. The latest post on the website, below, “lays out the evidence for wearing masks, talks about the development of a vaccine, and answers questions about the validity of the rapid nasal swab test.” You can read it as a whole, or skip to the “bottom line” in each section. I’ll simply list the sections (Q&A’s) and the bottom lines.

Alex has kindly volunteered to answer readers’ questions about the pandemic, about vaccinations, about masks, and anything to do with the virus and how we should deal with it as individuals and as a society. So feel free to put your questions in the comments, and Alex will answer them as he has time.

Click on the screenshot to read the post:


The sections and “bottom lines” (quotes are indented). Any take I have will be flush left, and of course each section below is followed in Alex’s post by an extensive discussion of the medical/scientific data.

Question: Will the wearing of masks in appropriate circumstances slow the pandemic?

Answer:  Probably.

BOTTOM LINE: The only way we’ll ever know for certain if mask-wearing by asymptomatic people, in the right circumstances, will reduce the spread of SARS-CoV-2 would be to prospectively assign a region (e.g., a city) to wear masks and compare its rates of infection over the same time to another region where people were assigned not to wear masks (and measure the compliance of each). The impossibility of conducting such a study at this point is obvious. Therefore, we’ll likely never be able to conclude with 100 percent certainty that mask-wearing in the right circumstances will slow the progression of the pandemic. But when we consider the sum of the evidence above, we conclude that mask-wearing by asymptomatic people, in the right circumstances, is likely to slow the progression of the pandemic.


Question: Who should wear masks, then?

Answer: Everybody.

. . . .When you consider this data together, you have what seems on the surface to be a good argument for not wearing masks to reduce the spread of COVID-19 if you’re asymptomatic.

BOTTOM LINE: But it’s not. Here’s why: a 21 percent prevalence of asymptomatic SARS-CoV-2 infection represents 57.9M people infected. If each of those 57.9M infected people has a 0.33 percent chance of spreading the infection without wearing a mask and does so, it would amount to roughly 191,070 transmitted infections! (Even if our estimate of the number of asymptomatic infections is off by a factor of 10, this would still amount to 19,107 infections.) We don’t know to what degree wearing a mask will decrease the risk down from 0.33 percent, but even a small amount would translate into a large number of people. Thus, while the impact of one asymptomatically infected person not wearing a mask is small, the impact of all asymptomatically infected people not wearing masks may be large. The logic of collective action requires that individuals act as if their contribution is greater than it is because only that way do enough individuals act in such a way that yields the protection society needs. We all need to tolerate inconvenience to contribute to the greater good.

Alex also discusses which masks are best. So far there are data only for which masks keep you from spreading viruses through respiratory droplets. For this N95s are the gold standard, but plebes like us can’t easily get them. He recommends using surgical masks to prevent infecting others, though most other masks seem to be about as good. And the best masks to protect YOU are probably the best masks for protecting others against you, though this isn’t 100% certain. Avoid knitted masks and single-layer cloth masks. I covered some research on this in a post a few weeks ago.


To me, this is the most depressing part, but I can’t quarrel with the argument:

Question: Will we have a safe, effective vaccine for COVID-19, and if so, when?

Answer: Probably. But likely not until the Summer of 2021 at the very earliest.

BOTTOM LINE: Currently, there are over 140 COVID-19 vaccines in development. Given the statistics we quoted above, that means we should end up with 14 viable vaccines. There’s one RNA vaccine being tested in a Phase III trial right now with 30,000 volunteers being given the vaccine. But we predict it will take us at least until mid- or late-2021 to determine if it’s a winner because it will take at least that long to make sure the vaccine is safe and effective. Remember, the risk of adverse reactions to vaccines needs to be substantially lower than the risk of adverse reactions to medications. This is because: 1) the number of people vaccinated will be much greater than the number of people given a medication (medications for diseases are given to at most millions of people; a vaccine for COVID-19 will be given to billions of people), so even small risks of harm can mean harm is done to millions of people, and 2) the vaccines are given to healthy people, not people already suffering from a disease. Thus, the risk of adverse events from the vaccine must be compared to the risk of not just contracting the disease but of experiencing a severe adverse outcome (i.e., severe, chronic morbidity or death). So, in the case of COVID-19, if we’re considering immunizing a 12-year-old child, for example, whose risk of dying from COVID-19 is literally only 0.022 percent, the risk of a severe adverse reaction to the vaccine needs to be far below that.

Unfortunately, the history of vaccine development is replete with stories of harm. One vaccine developed against respiratory syncytial virus (RSV) in the 1960s actually caused a form of immune enhancement where the disease was worse in vaccinated children, even killing two who’d been vaccinated. In 1955, Cutter Laboratories, a small pharmaceutical company that manufactured a polio vaccine, released vaccines contaminated with fully live virus due to manufacturing errors and poor government oversight, resulting in an estimated 40,000 children being infected with polio. Two hundred victims were permanently paralyzed, and ten of them died.

We mention these cautionary tales not to add fuel the anti-vaccine movement fire, but to highlight the importance of doing the science correctly, of not rushing inadequately tested vaccines to market. The reason vaccines are among the safest of medical interventions available is because they undergo such long and rigorous safety testing. As candidates come off the pipeline, we’ll review their efficacy and safety data and make recommendations about them.

This section has a good precis on how vaccines are both developed and tested. There’s also a nice graph in this section showing the reduction of nine childhood diseases after vaccination was introduced—good ammunition against antivaxers. Alex concludes: “Immunization is one of the most effective—and safest—public health measures that exist. The prevalence of infections from diseases for which we now vaccinate children has declined by ninety percent (see chart below of effectiveness of routine childhood vaccinations). There are literally no other interventions in medicine that are as effective as vaccination.”


Question: Are rapid tests worth doing, especially because the results are returned so much more rapidly

Answer: Only if the rapid test comes back positive can you believe it.

BOTTOM LINE: We don’t recommend people get a rapid test. Even though results take longer with the PCR test, a negative PCR test is more likely to be accurate. We know only one rapid test with a zero false-positive rate. Other rapid tests may not perform nearly as well.


This is the tenth in Alex’s series of posts on coronavirus and the pandemic; you can see all the links at the bottom of this post. There’s a lot more to read if you’re interested.

So, if you have questions—my latest one, which I asked Alex yesterday, was “is it safe to get a haircut, and how should ensure that the experience is the safest possible?”—put them in the comments below and then check back in a while to see if they’ve been answered.

Thanks to Alex for offering his analyses and advice to the readers.

75 thoughts on “Dr. Alex’s latest advice on Covid 19, and a chance to ask questions

  1. Hi Dr. Lickerman, Thanks for taking questions.
    I have seen statistics claiming that people over 70 are 200 times more likely to die from Covid 19 than young people (25 years old). I’m 77 and healthy.
    Question 1: Are there data on the relative risks of death for healthy old people?. Any journal references on this topic? Thanks
    Question 2: Very bad permanent side effects such as organ damage seem to often follow infection with SARS-CoV-2 (I’ve seen numbers of 30% or more). On the milder side, 60% of infected people have an enlarged heart 3 months after infection. Are these numbers valid, and again are data available related to age? Any journal references on this topic?
    Thanks again Dr. Lickerman for taking the time to answer our questions; Charles Sawicki

    1. Hi, Charles,

      The relative risk of death isn’t as important as the absolute risk of death. The last study I saw on this broken down by age is here: https://www.medrxiv.org/content/10.1101/2020.03.04.20031104v1.full.pdf.

      It showed that for people of your age, the absolute risk of death is 9.8% (children under 9, in contrast, if you’re interested in the relative risk of death, have a 0.0094% risk of death). But not all 77-year-olds are created equal. Those with co-morbidities like obesity, heart disease, kidney disease, and lung disease contribute to pulling that risk of death up for 77-year-olds.

      Regarding chronic complications of COVID-19, it’s way too early to tell. We are observing some things related to immune activation and persistent inflammation, but we’ve seen heart failure following other viral infections before. I haven’t seen data suggesting that 60% of people have an enlarged heart 3 months after infection. I saw one case report of a 58-year-old woman who had acute heart failure after co-infection with COVID and influenza, but that’s about it.

  2. In Illinois for the last month the daily count of new infections has spiked to around the 2,000 mark, much higher than the preceding month. Yet, there hasn’t been a similar uptick in deaths. They have been around 30 or less per day. At first, we were told that there is a lag between an uptick in new cases and an uptick in deaths of about two weeks. But, the two week period has long passed. So, if, in fact, the lag period has passed, what else can explain the relatively low death count? Could it be due to the virus mutating to a less virulent form, better treatments, younger people rather than older people now more likely to be infected, a combination of these, or something else? Your thoughts would be appreciated.

    1. I don’t know if anyone knows the answer, but we are seeing a greater proportion of younger people, who have a lower risk of death from the virus, accounting for a greater proportion of cases, so that’s probably a factor. We’ve also learned to care for COVID patients better (one study suggested mortality rates in ICUs have come down over time). We’ve also discovered that in the very sick (those requiring oxygen or in the ICU on a vent) that dexamethasone, a steroid, reduces mortality. I don’t think we’ve seen clear evidence that there are less virulent strains now circulating. The virus does mutate, of course, as all viruses do, but so far the evidence suggests in nonsignificant ways.

      1. We also see an increasing number of people being tested. Instead of testing only people who show bad enough symptoms to go to the hospital, there’s a lot more elective testing going on now, so more of those estimated 57.9 million asymptomatic people are being found, increasing the case numbers without increasing the death numbers.

  3. What’s your view on the efficacy of the new convalescent plasma treatment, Dr. L.?

    Does it appear to have undergone sufficient testing protocols?

      1. Besides insufficient testing and uncertainty as to whether it works at all, IF convalescent plasma did work, what are the practical issues?

        1) I suppose it would depend on Ab titer in the convalescent individual, but in general how many patients might be expected to be treated from one unit of blood from a convalescent individual? Guessing that this number is somewhere between one and 100.

        2) I assume that the health status of the donor comes into play as to how risky it is to even take a blood draw. Any thoughts in that area?

        3) Are you aware of any studies on what viral epitopes are being recognized by human immune systems? Are all patients pretty well producing antibodies to just one viral epitope, or is there a fairly wide spectrum with the preponderant epitope being one of, say, ten, with considerable variation patient-to-patient?

        1. 1. I don’t know.
          2. Patients who donate plasma are screened in the same way patients who donate blood are. No more–and no less–risky than that.
          3. What I’ve seen is that we produce antibodies to more than one epitope and not all produced antibodies are “neutralizing antibodies,” or antibodies that actually aid in fighting infection.

          We really need a randomized, placebo-controlled trial of convalescent plasma with the right endpoint–mortality rate–to figure out if this is a path we should take at all.

          1. Thanks, and yes, more studies needed.

            And to add into the mix of what needs to be looked at, as I suppose you may have seen, it seems that many of us likely already have antibodies that will cross-react with SARS-CoV-2 epitopes, presumably from prior infection from related coronaviruses. I imagine that studies on people like asymptomatic carriers and based on this study are ongoing as we speak, but like with so much of this there simply hasn’t been enough time to gather all the data / come to any solid conclusion.

        1. So did I. The British NHS and others have been conducting trials for a couple of months at least but I am unaware of anything “new” other than Trump announcing the FDA emergency use authorisation as if it’s some major breakthrough on a level with hydroxychloroquine.

          1. At least it has a better chance of being useful than injecting yourself with bleach or sticking up a a UV lights up your nether parts. 🙂

  4. …it would amount to roughly 191,070 transmitted infections!

    Even if we assume that all of these infections would have been prevented by wearing masks, i.e. that masks are 100% effective, why should we care enough for “everyone” to change their behavior? Doesn’t this translate into only 5000-odd deaths, a miniscule number considering the 2.5 million per year who die from “normal” diseases that we hardly give a moment’s thought to?

    1. When considering the relative numbers of deaths from different causes, it’s easy to forget that each number represents a human being. And each of those deaths also represents suffering for all their loved ones and friends. Certainly 5,000 deaths is minuscule compared to the total number of deaths on the planet per year, but it’s also larger than the number of deaths that occurred on 9/11. These are preventable deaths, so why would we argue not to make the effort to prevent them, especially when the effort required is so minimal?

      1. It’s not clear that the effort required is minimal. If we all wear masks, can we reopen schools and businesses and otherwise return to a normal life? Or is shutting down the economy and putting tens of millions of people out of work also a necessary part of the effort?

        I think the response to 9/11 was greatly overblown. Two new wars costing trillions? We have a 9/11 every 40 hours due to heart disease, but we aren’t spending much money or national effort trying to improve our diet and lifestyle.

        I’ll accept this argument when people start showing proportionate concern for other causes of death. Yes, each of those 5000 people is a person. But what about the 600,000 people who die from cancer every year? We’ve shelled out trillions of dollars for coronavirus and are slated to pay trillions more and yet our cancer research budget is only about six billion… The money we’ve spent on coronabucks alone so far could have funded over 300 years’ worth of cancer research. We have reports including here on this website of people whose cancer screenings and treatments were canceled or delayed because of COVID-19, and estimates of tens of thousands of resulting excess cancer deaths. Why are COVID victims’ lives so much more important than cancer victims’ lives, as evidenced by the massively disproportionate investment of media time and national resources?

        Finally, COVID overwhelmingly kills people who are near the ends of their lives. The median age of those who die approximately equals the normal life expectancy. When you’re 80 years old with aggravating health conditions (which ~99% of COVID victims had), something’s going to get you, so it’s not clear that their deaths were preventable in the sense that they wouldn’t have died this year from the flu or heart disease instead, whereas the excess suicide, drug overdose, and cancer victims’ lives truly are being cut short.

        So I still have to ask “Why care so much about COVID but not these other things?”

        1. I’m not arguing any of the points you’re making. I’m not saying anything about the decision to shut down the economy. I’m not saying there aren’t significant consequences that have resulted from doing that, many of them non-COVID health-related.

          But are you arguing that because you think other things haven’t received the appropriate attention and emphasis that we should therefore not adopt an intervention (mask wearing) that’s likely to slow the spread of the pandemic? Perhaps you disagree with my conclusion that it likely will slow the pandemic and therefore that we shouldn’t wear masks; that, at least, would be an understandable argument.

          I hear the anger you feel about how the pandemic has been (mis)handled, about how resources have been allocated. But I fail to understand what all that has to do with the idea that we should all wear masks indoors to prevent the spread of the pandemic.

          1. I have nothing against people voluntarily following good advice, and I do appreciate your effects to educate and advise people based on facts.

            I just consider the whole thing irrational. Are we operating on principle or panic? If we want to minimize deaths by disease or preventable deaths generally, a rational health policy would focus on the biggest causes of death and those where we can save the most lives per dollar. I can support a rational policy, but this is clearly a mass panic, and to be forced out of a job and into a mask on the basis of a panic really rankles. If voluntary measures are good enough for diseases that kill orders of magnitude more people, why must we submit to force in this case? Rhetorical question.

            1. You are unnecessarily conflating “wearing a mask” and “shutting down the economy”. Wearing a mask is a very small burden: millions of Muslim women have been doing something equivalent, with no adverse health consequences (I am NOT suggesting this practice is desirable, just or equitable.)

              So I do not understand how wearing a mask in public spaces is more of a burden than wearing pants.

            2. “diseases that kill orders of magnitude more people”

              Which diseases are those, Adam? Every week we’re experiencing an equivalent of two+ 9/11 events. The only thing keeping those numbers from being far greater is the social distancing and mask wearing that you seem to find oppressive. But the “whole thing” is “irrational”?

        2. All of those other arguments enter into ‘what-a-boutery’ territory, and I have not yet seen how that is ever a valid argument. Such arguments automatically discredit themselves. There are two replies that I have.
          1. Unlike all those other factors (cancer, etc.), the risk of infection, harm, and death is transferred to other people who do not want to be infected and are trying to not be. And once infected, they have a good chance of passing it on to their trusted family and friends who also did not want to be infected. It would be nice if the risks of infection was confined to just those who want their ‘just carry on’ lifestyle, but that is not the case.
          2. Unlike those other risks and dangers, Covid-19 is a virus and it has a tendency to grow exponentially. While is is a lower danger to some other dangerous things, it can quickly become far more prevalent. Holocaust levels and beyond.
          3. Three things, really. Don’t write off the value of the lives of old people. And even where young people usually weather thru the disease, a fraction of them don’t And as this becomes more common that fraction means a very large number.
          It is being between a rock and a hard place, that is for sure.

    2. There are 273.6 million motor vehicles in the US equipped with them, yet seat belts save just 15,000 US live annually.

      Should we stop buckling up? Stop requiring manufacturers to provide seat belts as standard equipment?

      1. Sure, why not? It’s hard to think of a risky activity that imposes less direct risk to others than not wearing your seat belt. (I guess you could fly out a window and hit a pedestrian…)

        I expect people are so accustomed to wearing seat belts now that they’d refuse to buy cars without them. The manufacturing requirement for seat belts probably isn’t needed anymore because the culture was successfully changed. It’s a real success story for cultural engineering by force.

        Should we force other cultural changes? We could save a lot more lives than that if we stopped drinking alcohol. Do we really need to intoxicate ourselves? Sure, we may like that drug, but we could eliminate tens of thousands of annual cirrhosis and drunk driving deaths.

        Do we really need to drive 65 MPH rather than 55? We could save a lot of lives if we just drove slower, and that’s really not much to ask, is it? Only a deviant would put his need for speed over the lives of others…

        1. Now if we could just get rid of OSHA and those busybodies at the Underwriters Laboratories we’d have ourselves a libertarian paradise, huh?

          1. Well, if even 10% of the stuff in The Jungle was true, it’d be enough to enrage any fair-minded person. But the government requiring people to wear seat belts and bicycle helmets is just nannyism. The argument that you might cost tax payers money doesn’t make sense to me and is clearly more of a justification than a principle; it’s much less intrusive for the government to simply refuse to pay for your care if you get hurt due to not wearing a seat belt or helmet.

            1. Why limit the government’s refusal to pay for medical care when a person gets hurt not wearing a seat belt?

              Let’s consider this situation in a libertarian paradise. A person without health insurance goes to the ER, obviously very sick. Here’s the dialogue.

              Patient: Nurse, I am not feeling well.
              Nurse: First things first. What’s your insurance?
              Patient: I don’t have any. I am a free man and, as such, I don’t think I need it. I sure as hell wasn’t going to let the government force me to buy it, even though I could afford it.
              Nurse: O.K. sir, since you don’t have insurance, we’ll need a down payment of $10,000 right now. Can you pay now?
              Patient: No, I can’t.
              Nurse: You have to leave now. No payment, no service. That’s the libertarian way – Freedom and individual responsibility.
              Patient: But, I’m sick.
              Nurse: Tough luck. Why don’t you see how Ayn Rand would handle the situation.
              Nurse: Oh, look now, he’s collapsed on the floor.
              Doctor: Too bad, he’s dead.
              Nurse: Well, get that body out of here. Dump it somewhere. I have paying customers to deal with.
              Doctor: O.K. I’ll get an orderly to move it. What’s most important to remember is that he died a FREE man. No f—-ing jackboot government was going to tell him what to do.
              Nurse: Yes, that’s exactly the way things should be.

            2. I do wonder about bicycle helmets. The City of Seattle has nanny nagged us for years about bike helmets, and has a fine for not wearing one. Unless. When bicycle share companies opened up a few years ago, they could not provide helmets. The City now exempts people riding bike shares from wearing helmets, while you must wear a helmet riding your own bike. Where is the logic in that?

              1. A neurosurgeon colleague of mine had a great demo he did in schools. He’d take a small watermelon with attached bike helmet and drop it helmet first on the stage from chest height. Then he would drop another one sans helmet from the same height and then say – thank you for your attention.

        2. I suppose Adam M.’s seatbelt argument could be discussed and statistics be weighed. It would seem that it is the same argument as refusing measles vaccination along the lines of “Nobody has measles anymore, so why vaccinate?” And here we are, with people suffering and dying from a preventable disease.

        3. Here in the UK, rear seatbelts were made mandatory a couple of years after front seatbelts. People in the front of the vehicle were no longer being killed by being thrown through the windscreen in the event of a collision. Instead, they were killed by unrestrained rear seat passengers being flung forward. (Not sure how the safety experts didn’t see that one coming.)

          So someone’s decision to exercise their individual right to not wear a seatbelt could still kill me, if I’m sat in front of them.

        4. Wearing a mask in public is a goal easily achieved, like getting people to wear seat belts.
          Giving up alcohol is not. Even the most draconian measures do not achieve that. We saw that during Prohibition or during the recent alcohol sales ban in South Africa. The comparison is flawed.

        5. You seem to have missed two aspects of this problem: exponential growth of the virus swiftly overburdening the medical system (which affects and endangers everyone), and the fact that if it’s left up to people to “voluntarily” wear a mask, the non-maskers endanger the mask-wearers.

          Here in Germany schools are open quite safely on the whole (so far), and businesses are functioning again ok, more or less. That’s because the government took responsibility for the task of educating the public about the dangers and convincing them to wear a mask.

          In comparison, both the US and the UK have political leadership that is by their nature averse to talking factually and honestly with the public.

  5. I’m sorry, but I think the calculation that leads to there being 21% of the population infected but asymptomatic is faulty. You can’t base a calculation of the number of asymptomatic cases at any one time on the cumulative total of cases over the course of the whole pandemic. It’s nonsense.

    Since May, the UK Office of National Statistics has bee conducting a survey of coronavirus cases in England. They take random households and test everybody in the household for COVID19. From this they gain an estimate of the number of people in the country with COVID19 both symptomatic and asymptomatic.

    In the first period for which results are available they estimated that 148,000 people in England had the virus (excluding cases in hospitals and care homes) with a 95% confidence interval of 94,000 to 222,000. If we take the high estimate and assume all of those cases were asymptomatic (they weren’t), we end up with 0.4% of the population were asymptomatic carriers of COVID19 at a time when our deaths and infection rates were at least as bad (probably significantly worse, in fact) as the US’s deaths and infections now.

    I understand that the COVID19 test has a high false negative rate, but even so, 21% is surely wrong by at least an order of magnitude.

    1. I don’t actually disagree. I was making a worst-case scenario calculation. You make two important points: 1) using the total number of cases recorded thus far as the prevalence, as I do, will produce an overestimate of the true prevalence, and 2) I don’t really believe 21% of the population is asympomatically infected. I was using earlier data suggesting the total number of symptomatically infected patients might be as high as ten times the number of TESTED symptomatically infected patients, as well as data suggesting the number of asymptomatic patients is equal to the number of symptomatic patients (other studies have placed that number at only 20%). These are worse-case guestimates. However, given that the true prevalence of asymptomatic cases IS likely orders of magnitude lower than 21%, the positive predictive values of both the PCR test and antibody tests are going to be low when testing asymptomatic patients, which means it’s really hard to get an accurate picture of what the asymptomatic rate really is. But as I wrote in the post, even if it’s 10 times less that I supposed, the absolute numbers of cases we’d prevent by wearing masks indoors is still large. The number of deaths we’d prevent by preventing those cases would be smaller still, but not, at least in my mind, insignificant.

  6. Thanks for taking questions. Is it safe to go to a gym? I miss the gym, but I’m 73 and I have asthma (very mild; haven’t had to use an inhaler for years, but I have had some fairly severe reactions). My gym has reopened, but I have been reluctant to go back. Do the benefits of regular exercise outweigh the risks?

    A second question is about my 2 year-old grandson. I worry because he isn’t around other children. His parents are able to arrange work schedules so that one or the other cares for the child. Prior to the COVID shut downs, he could go to playgrounds, library story hours, community events where there were other children, birthday parties. Now he is really isolated — no neighborhood children, no family close by, no siblings. What are the risks of sending young kids to preschools?

    1. Gyms: depends on the measures being taken. Presuming that no one with any symptoms of infection sets foot in the gym, your only risk is catching it from someone who’s asymptomatic. As I commented in another thread, I think the true asymptomatic prevalence is far lower than 21%. If everyone in the gym around you is wearing a mask correctly and consistently, and you are as well, I think the risk is quite low, on the order of 0.33 percent or lower of you contracting COVID.

      Preschools: harder to say. Children under 9 seem to be less likely to be infected and less likely to transmit the infection. Whether or not your grandson can go back to pre-school is a topic beyond what I can fit in a simple comment.

    2. This are 2 good questions.
      Wearing a mask is already uncomfortable when you are breathing normally, who is going to wear one while working out? My gym doesn’t have any windows and the air is on all the time. Because of that I think the risk is too high. Specially if the particles can stay in the air in closed spaces like that.

      1. Personally, I’ve found when doing a cardiovascular workout, even wearing a surgical mask is too uncomfortable, so I do those in isolation or outside. I find I don’t become short of breath wearing a surgical mask while weight lifting, though.

    3. There may be ways for kids to ‘co-isolate’. That is, they form play groups with a few other children who are also otherwise well isolated. For that to work, the parents need to be in full agreement to avoid doing things that increase the risk to the group. If they attend a social gathering, they quarantine themselves afterwards. Finding such a group may involve making inquiries.

  7. Thanks for taking questions Is it safe to go to a gym? I miss the gym, but I’m 73 and I have asthma. My gym has reopened, but I have been reluctant to go back. Do the benefits of regular exercise outweigh the risks for us older folk?

    A second question is about my 2 year-old grandson. I worry because he isn’t around other children. His parents are able to arrange work schedules so that one or the other cares for the child. He has never been in daycare. Prior to the COVID shut downs, he could go to playgrounds, library story hours, birthday parties, family and community events. Now he is really isolated: no neighborhood children, no family close by, no siblings. What are the risks of having him in preschool versus benefits of being with other children?

  8. Thanks for the thorough write up. Curious to hear your view on outdoor mark wearing when socially distanced. For example, I often go on long bike rides on streets and trails. I see some people wear masks when doing so, while others do not. Given I’m riding quickly and the fact that I rarely ride within 6 feet of people (but occasionally do if passing someone on a trail), it seems unlikely a mask would add much value. However, I want to make sure I do the right thing. Would love an expert opinion on this.

    1. With the caveats that we don’t yet know what an infectious dose of SARS-CoV-2 is (that is, the amount of virus required to cause an infection), I think it highly unlikely that mask wearing outside when appropriately socially distanced adds much, if anything, to reducing the risk of transmission. In the unlikely event that someone asymptomatically infected and not wearing a mask sneezes or coughs on you, you might become infected. But I’ll confess here I walk my dog maskless. I don’t think it’s necessary to wear a mask when riding a bike outdoors.

        1. That makes sense to me too. I’m one of those maskless cyclists. When I approach someone else on the path (although I try to do most of my riding on the road), I time my breathing so I take a nice long inhalation before I reach the person, hold my breath a moment as I pass, and then exhale. Easy to do (maybe easier for cyclists where the speeds are higher than for hikers). The disadvantage is that you’re not virtue-signalling to the people you meet, so some of them still think you’re a jerk.

          1. Can relate to that. Feel like I’m often being judged as a jerk, and yet I also adhere to holding my breath and now at least I have a doctor supporting my decision. I don’t mind wearing a mask when walking about outside, even socially distanced, as a signal of the importance of being careful and being responsible. But if I’m doing a two hour bike ride, wearing a mask the entire time is less than ideal, especially if it’s not doing anything useful to prevent spread.

  9. How would you rate the risk of staying in lodging right now, Dr. Lickerman? We are thinking of spending a few nights on the Coast in a small town where the incidence is low, but is popular with tourists. It is a high-end place, but we know that is no guarantee. We are taking our own pillows and sanitizing supplies even though the establishment promises the highest level of safety. We will sanitize all surfaces we are likely to touch and use, and decline housekeeping services while we are there. Can you recommend any other precautions if we go?

    1. The likelihood of contracting the virus from surfaces is looking quite low. The risk is being around other people. If you’re careful to avoid touching your face and wash your hands frequently, the biggest risk of staying in lodging is being around other people indoors who aren’t masked. If you can avoid that, I think it’s safe.

  10. I have heard lots of different ideas about herd immunity. Some people are claiming that it could be as low as 20% and others are estimating closer to 60%. Do you have any thoughts?

    If it is on the low end, could it actually be good if young, healthy people get the disease now reducing the cases among the old and vulnerable later?

    1. In the 1970s, we recognized that if the the proportion of people in the population who developed immunity exceeded (R0-1)/R0, where R0 is the average number of people each infected person will infect, that the incidence of the infection would decline. With COVID-19, R0 is still evolving, but I’d guess will end up somewhere around 2-3. So if we say 3, then 3-1/3 is roughly 66% of the population needing to have immunity to COVID-19 to see the pandemic come under control. See this: https://academic.oup.com/cid/article/52/7/911/299077

  11. Thanks for taking questions.

    What is your opinion on transatlantic air travel?
    Is there a trustworthy source for the effectiveness of the HEPA air filtering on planes?
    I am 74, so the almost 10% of death risk is a bit scary…

    1. Hard to answer this one. Data from Asian contact tracing studies suggests the risk of acquiring COVID-19 on public transportation, e.g., trains and buses, is 0.1% only. In these studies, commuters wore masks consistently. I don’t know how well the HEPA air filters on planes filter this virus, but if everyone is wearing a mask consistently on the plane, the risk should be quite low. The issue is, can you be guaranteed that on a trans-Atlantic flight that everyone will wear their masks correctly and for the entire flight? My personal experience on domestic flights suggests not. But if no one symptomatic gets on the flight (again, how confident can we be about that?), I think the risk overall is still low. If you are at a higher risk for dying from COVID or your reason for trans-Atlantic travel isn’t pressing, you might want to consider even the low risk I quoted above to be too great. It’s a value judgment.

  12. Alex, I’m happy to see you changed your stance on masks.
    I’ve been slammed and ridiculed for promoting masks during the early stages of the epidemic (not here on WEIT), but I feel kinda vindicated now.
    Only the real ‘good’ ones can admit they were wrong and change their stance: kudos to you.

    1. Thanks. In all things, I try to follow the data. It’s been fascinating to watch how the world reacts to seeing science happen in real-time, watching the “sausage” get made, with all the caveats and reversals that it entails.

  13. I don’t have any personal questions or concerns about coronavirus / Covid-19 not already answered above. However, I – and I’m sure very many other WEIT readers – greatly appreciate Dr Lickerman’s willingness to freely give his expert advice on this and previous occasions.

  14. Remember not all masks are alike. I would suggest all governments supply two free masks to everyone – reusable & made to a high standard. Single use masks should be banned – I have seen a lot discarded by morons & seen pictures of a gull, caught in one, that had to be rescued.

  15. Hi Dr Lickerman,
    Thanks for taking questions, and for your answers so far. Your observation on the public getting to see the ‘sausage” being made is really interesting, it also made me laugh to be fair! It highlights the ignorance of the media – and therefore the public – regarding the process of science and evidence-based medicine. The cynical part of me is inclined to view this largely as a function of media irresponsibility. Ratings are rarely boosted by a sober interpretation of evidence – at least in the short term.
    That said, I’d also like to ask a question if I may. Over the last couple of days there have been press reports of COVID-19 re-infection, I learned about one report it here: <a href="Independent Article – COVID-19 , the article linked to what looks like a very early version of a paper: Paper – COVID-19. The authors conclude that a healthy patient was re-infected with COVID-19, approximately 4.5 months after first contracting the infection. To my untrained eye this raises concerns regarding the efficacy that we might be able to expect of a COVID-19 vaccine.
    The reports suggest acquired immunity against COVID-19 infection wears off in some people after just a few months. As I understand it, this acquired immunity is dependent on the presence of sufficient quantities of antibodies which can bind to the COVID-19 particles. I further understand that the goal of vaccination is to generate such antibodies in sufficient quantities to ward off infection by the virus. If an actual infection doesn’t always confer long-lasting immunity, can we expect any better or any worse from a vaccine? Do the reports of re-infection suggest a vaccine might be ineffective, or effective only for short periods? Might a patient require frequent on-going top-ups to retain immunity?
    I realise there may be a few assumptions in my reasoning here, and that much depends on further research. I’m hoping my pessimism is unwarranted and would be interested to hear your take.

    Many thanks,

    1. Jeff,
      You’re asking excellent questions. It’s known that people who contract seasonal coronavirus, which has about an 85% similar structure to SARS-CoV-2 (which causes COVID-19), can get it again within months. Natural immunity may very well be temporary. However, depending on the vaccine strategy, immunity from a vaccine can be much longer. Sometimes, we have to give booster shots as immunity from some vaccines can wane. But evn if natural immunity may not be long-lasting, vaccine-induced immunity still can be. This is what Phase III trials are designed to tell us.

      1. Dr Lickerman, I wonder if you could elaborate on the point that immunity from vaccine could last longer than immunity from natural infection. Intuitively it would seem like a vaccine presents a less lethal attack to the body and as such the immune response would be less powerful, including a shorter lasting memory.

        Are there explicit examples of previously developed vaccines which generate longer lasting immunity than the corresponding natural infection?

        1. Vaccines can be directed at specific parts of infectious agents that the body’s own immune system doesn’t react to strongly but that produce antibodies that yield greater and longer lasting protection. One example: the shingles vaccine. The herpes virus that causes shingles lives dormantly in dorsal nerve root ganglia in the spine and becomes reactivated during times of stress. The new shingles vaccine, Shingrix, prevents this at a remarkably high rate, far beyond what natural immunity is able to accomplish.

          1. This information on vaccination is reassuring and also very interesting. Thanks for taking the time out to help!

  16. Thanks a lot for taking readers’ questions.

    Apologies if this has been answered and I missed it but at one point I heard that the widespread covid-19 test, though it does have a low false positive rate , actually has a relatively high false-negative rate. Is this true? If so, it seems rather alarming. Caveat: I am in Ontario, Canada. Not sure whether a different test might be used here.

  17. Writing from Sweden – were masks are not used since there is scant evidence that it works in a pandemic – I have to ask why “first, do no harm” is so important for vaccines but not for masks?

    I’m fairly sure this is a poor study and inflated for political reasons [consider the source; I haven’t read the study], but it points to the general problem in this situation:

    Wearing face masks can lull people into a false sense of security — making them more careless and less likely to follow social distancing rules, a study has found.

    Psychologists from the Warwick Business School found that people felt more comfortable sitting or standing closer to others while wearing a mask.

    Furthermore, people appear happy to keep a smaller distance from other who are also wearing face masks, the researchers reported.

    These effects were more pronounced among those people who believe that face masks are effective at preventing the spread of coronavirus.

    Given this, it could be difficult now to reestablish social distancing measures if they are needed in the event of a second wave of cases, the researchers warned.

    The results appear to support the opinion of the Swedish Public Health Agency’s chief epidemiologist, Anders Tegnell, who has been critical of face masks.

    He said that the evidence in support of their effectiveness is ‘astonishingly weak’ and that they encourage people to feel complacent about gathering in close proximity.

    However, the findings contradict those of another recent study, which concluded that face mask wearers are 13 times more likely to keep up social distancing.

    ‘Our results could be particularly relevant for countries where mask usage is now high, but social distancing guidelines have been relaxed,’ said paper author and behavioural scientist Daniel Read, also of the Warwick Business School.

    ‘If countries need to return to greater levels of physical distancing due to a second wave of cases, that may be harder to implement than it was when mask use was low at the start of the pandemic.’

    ‘We need more evidence to determine at what point the risks of reducing physical distance outweigh the benefits of wearing a mask,’ he added.

    ‘Clearly, the greatest benefit results from using masks to complement social distancing, rather than replacing it.’

    [ https://www.msn.com/en-us/health/wellness/face-masks-make-people-less-likely-to-follow-social-distancing-rules/ar-BB18kDfW?li=BBnbfcL ]

    1. I should also add that Folkhälsomyndigheten now inform us that it is considering mask wearing for situations were social distancing isn’t enough. (Against a situation were we will face local flare ups since the epidemic wave is curbed – so not the US situation of rampant epidemic. FWIW, we didn’t need masks to get there, social distancing and hand washing suffice.)

      But among considerations is how to ensure that you can supply sufficiently many masks when needed, especially for those who cannot afford them.

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