Dr. Lickerman on coronavirus: is a vaccine in the offing, what’s your risk of infection from casual contact, and what rules should businesses follow if they’re allowed to reopen?

May 14, 2020 • 10:45 am

I’m calling attention to a new post by my physician, Dr. Alex Lickerman—part of his continuing series on the pandemic and the virus.  In this one, he lays out guidelines about how a business should operate to be opened safely if it’s allowed to and wants to; but he emphasizes at the outset that he is not recommending that businesses reopen:

If we consider the public health perspective only, maintaining the stay-at-home order still makes the most sense. We still don’t have a vaccine or effective treatment that lowers the mortality rate of COVID-19. Whenever large enough groups of people gather, there will be increases in the number of cases. Flattening the curve by maintaining the stay-at-home order spreads those increases out over time so that the healthcare system isn’t overwhelmed and everyone who needs a ventilator gets one.

and adds this:

So our purpose with this post isn’t to tell you whether or not reopen your business—that’s a judgment each of you have to make on your own—but rather to provide recommendations that will minimize the risk to your business and your employees if you do decide to reopen. We recognize that people are afraid both of contracting COVID-19 and of worsening economic disaster. Both fears are legitimate. But we think all decisions should be made based on science and statistics, not emotion. Our intent, then, is to provide you with the most accurate, up-to-date evidence-based statistics possible.

In fact, most of the post is devoted to discussing whether a useful vaccine is in the offing and what your chances are of contracting the virus from others, including those who are asymptomatic. The guidelines for opening a relatively safe business is at the end of the piece, and I’ll let you read that for yourself.

Click on the screenshot to read. Alex will be reading the thread from time to time, so feel free to ask him questions. 

The stuff that interested me are two issues?

1.) What’s the story with a vaccine? And it’s worse than I thought. Not only will it take time to develop any vaccine, but it may not be possible to produce an efficacious vaccine at all:

Some have been thinking that we can’t fully reopen the economy until we have a vaccine. But how soon might that happen? We don’t know. We might never. We still don’t have one for hepatitis C or HIV. But even if we do develop one (and many are currently in the works), proving it both to be safe and effective will take time. To deliberately infect volunteers who’ve been vaccinated against SARS-CoV-2 to see if they’re immune would be unethical given the fact that the disease is fatal in some cases (you can do this with animals, but animals aren’t humans). Instead, once we have a viable vaccine candidate that’s passed Phase 1 and 2 trials, we immunize a large group of people and follow them through time, comparing their rates of COVID-19 infection to a matched group that hasn’t been immunized, all while observing for complications that didn’t show up in the Phase 1 or 2 trials.

Unfortunately, sometimes the treatment is worse than the disease. Studies show that when given immunizations to some diseases—dengue, respiratory syncytial virus, and SARS, for example—a paradoxical phenomenon occurs: subjects develop more severe disease. There are thought to be two mechanisms that cause this: 1) antibody-dependent enhancement, where a virus leverages the antibodies that we generate in response to vaccination to aid infection, and 2) cell-based enhancement, where immunization leads to severe allergic inflammation that can cause worse disease outcomes.

Unfortunately, vaccines used to induce mice to produce antibodies to the virus that causes SARS—a coronavirus similar to the virus that causes COVID-19—were shown to place the mice at high risk for life-threatening cell-based enhancement. Fortunately, when researchers altered their vaccine strategy and aimed to create a vaccine against only a portion of the spike protein of the SARS virus, cell-based enhancement was blocked. Sadly, funding dried up just as researchers were about to proceed to clinical trials in humans. Now, with the COVID-19 pandemic, that research is restarting.

Not only that, but even if you recover from the coronavirus, you may not have sufficient antibodies to mount a response to re-infection, much less show up on a test as having recovered from an infection. Alex’s bottom line is this:

We still don’t have a vaccine or know when or even if we will have one. We also don’t know if infection produces immunity, for how long that immunity might last, or if infection predisposes to a more severe course from re-infection.

2.) What kind of exposure to the infected or to asymptomatic carriers do you need to get the virus yourself?  Here the news is a bit better: it appears that you need pretty sustained exposure to someone who’s infected or to an asymptomatic carrier to get a high risk of getting the disease. In other words, you need “close contact”. Now that can be someone sneezing in your face or coughing at you, but simply being in the presence of others for a short while without those things happening (especially if you wear an effective mask, and cloth masks, while better than nothing, are not nearly as effective as surgical masks), doesn’t put you in extreme danger. A few excerpts:

Thus, it seems even when people ignore current social distancing guidelines, the risk of transmission is, in fact, low, and—given the much higher rate among household contacts—largely determined by amount of contact time a person has with an infected patient. This is likely because with more contact time, higher risk scenarios are more likely to occur, i.e., coughing without a mask on, touching shared surfaces and then one’s face, and so on. It seems it’s not quite as easy as many think to encounter an infectious dose of the SARS-CoV-2 virus.

. . . . What does all this mean? First, transmission rates from contact tracing studies seem to cluster under 1 percent or around 10-20 percent. The difference may be due to behavior differences in study subjects, to differences in average contact time of close contacts with index cases, or to methodological differences in the studies. Whatever the reason for the differences in attack rates, all the studies suggest that when you have close contact with an infected person, the risk of becoming infected is, in fact, relatively low. Consider also that what defined “close contact” behavior in the studies above is behavior that most of us are now doing our best to avoid (e.g., being closer than six feet to others for a prolonged period of time or having unprotected direct contact with infected secretions).

. . . .What this means, among other things, is that everyone must become strict about self-quarantining once they show any infectious symptoms whatsoever (including: sinus congestion, runny nose, sore throat, ear pain, cough, vomiting, diarrhea, fever, chills, body aches, loss of smell or taste, discolored toes). In America, we’ve endured a culture of going to work while sick that must now end.

As for asymptomatic carriers, the chance of getting it, even when you work in an office with someone (and who is doing that now), is also low:

How likely would you be to catch COVID-19 from an asymptomatic person working in the same office as you? Research suggests that if you do have the kind of sustained close contact with asymptomatic cases that occurs in households (a reasonable surrogate for a workplace), the risk of catching COVID-19 is only 0.33 percent (compared to a risk of 3.3 percent for sustained close contact with mildly symptomatic cases, a risk of 6.2 percent for sustained close contact with severely symptomatic cases, and a risk of 13.6 percent for sustained close contact with someone who’s coughing and expectorating, meaning bringing up phlegm).

So we have some bad news (vaccine) and some good news (you’re not in as much danger of being infected as you thought).

Here are Alex’s previous posts on the coronavirus:

  1. Coronavirus February 2020—Part 1 What We Know So Far
  2. Coronavirus March 2020—Part 2 Measures to Protect Yourself
  3. Supporting Employee Health During the Coronavirus Pandemic
  4. Coronavirus March 2020—Part 3 Symptoms and Risks
  5. Coronavirus March 2020—Part 4 The Truth about Hydroxychloroquine
  6. Coronavirus April 2020—Part 5 The Real Risk of Death
  7. Coronavirus April 2020—Part 6 Evaluating Diagnostic Tests
  8. Coronavirus April 2020—Part 7 The Accuracy of Our Antibody Test

55 thoughts on “Dr. Lickerman on coronavirus: is a vaccine in the offing, what’s your risk of infection from casual contact, and what rules should businesses follow if they’re allowed to reopen?

  1. In my reading of the post, this seems to be the most important sentence: “Evidence is accumulating, however, that sustained exposure to infected patients—whether those patients are symptomatic or not—is what largely determines the risk of transmission. “ In other words, Dr. Lickerman seems to be saying that casual contact with an infected person for a short period of time does not represent a substantial risk of infection. Of course, the word “sustained” is somewhat vague. Does it mean five minutes, an hour, or what? Also, the questioned is raised, why is this so, particularly when one is adjacent to a non-symptomatic, infected person? Is this because a certain quantity of virus must be transmitted before it becomes a danger to a non-infected person. In other words, is the viral load transmitted an important factor in determining whether a person becomes infected? I don’t know if there are answers currently available to these questions, but I sure would like to know.

    1. In the contact tracing studies, the cut off was more than 10-15 minutes of close contact (i.e., contact closer than 6 feet). The risk goes up with longer contact beyond that. Household contacts, who are presumably around each other for days at a time, still had very low rates of transmission. The answer to your second question is yes, you have to receive what’s called an infectious dose, meaning, a concentration of virus high enough to gain a foothold in your body, to become infected. In asymptomatic cases, the likelihood of receiving such an infectious dose is lower than in symptomatic cases, who almost certainly have higher viral loads to transmit. (The actual transmission rates of asymptomatic, mildly symptomatic, and severely symptomatic patients are quoted in my article. The differences are undoubtedly due to differing viral loads and therefore likelihood of transmitting and infectious dose to others).

      1. My mother is a cashier in a grocery store. She has been terrified of infection but has no choice but to keep going to work. In her position she has many short-term contacts per day but is otherwise able to avoid being close to any one person for long periods. Is the viral load cumulative? That is, if she has multiple small exposures in a day does it represent a similar risk as one long-contact exposure?

        Thank you so much for the informative posts and for taking the time to reply in the comments here.

        1. Great question. The likelihood varies with individual exposure to individual people. Multiple, small exposures doesn’t carry the same risk as one large, sustained exposure. The likelihood of your mom catching it while working in a grocery store is likely quite low.

          1. My wife also works at a grocery store part time. Thanks Neil for the question and thanks Alex for your answer. Some of my anxiety is alleviated.

  2. Thanks for this interesting and informative post.
    In the article it says, “Also, it should go without saying—but we need to say it because we’ve seen it—make sure your employees know not to pull their masks down to cough or sneeze.”
    My question, possibly naive, is what should the employee do instead? The thought of sneezing while wearing a mask is revolting. Would using a tissue to confine the cough or sneeze be acceptable?

    1. Yeah, I know, sneezing into a mask is nasty. But if you’re around others, it’s the very best way to prevent spread of virus if you’re infected, far better than sneezing or coughing into a tissue. You’d then just want to change your mask. Sorry!

        1. Thank you both for question and answer. Sneezing was something I had not even considered.

          I have only worn an official replaceable mask while visiting a senior relative. Felt hot, humid and basically uncomfortable. Had reading glasses on for a short time that even fogged up! Can only imagine the discomfort of those wearing these all the time.

  3. Good morning Dr.I am missing my dose of large Dairy Queen fries.When dealing with the drive through is there a safe way of dealing with the container? Transfer contents to my own container? Thoughts please

    1. When you initially touch the container, consider it and then your hands to be contaminated. When you get home, first wash your hands with soap and water. Then without allowing the container to touch your now clean hands, disinfect it with wipes or a lysol solution or with whatever else you’re using to disinfect surfaces. Then you’re good to go.

  4. Just as additional experience we made a trip to the vet yesterday for a cat. At the vet you do not go in. Stay in the car and call the office with your appointment info. They send someone out to the car to get your pet. The person coming out to the car is masked and has appropriate clothing. If any further info is needed they call you from the office to you in the car. Eventually you get the cat back, pay the bill and leave.

    1. I have three separate appointments scheduled for the end of the month doing exactly as you described. I think it’s nice of them to give the cats back even if they do charge me.

  5. What’s the deal with immunity? Does having had the virus provide immunity from catching it again or not?

    1. Bottom line is we don’t know. Seasonal coronaviruses (similar but not identical to the coronavirus that causes COVID-19) have been shown to infect children who then can get it again weeks or months later. We think some people probably do get some immunity for some amount of time, but until enough time passes for us to test that, we just won’t know. As I point out in the article, there’s some evidence that getting infected may put you at risk for a worse outcome if you catch it again. For now, if you are definitively diagnosed, I wouldn’t consider you immune, and I wouldn’t alter your social distancing behavior.

  6. This is an excellent article and I find his data encouraging. I especially like that he understands that both medical and economic issues are important.

    It would be great if a few doctors like him could get to together with some economists and business owners to try to craft policies for different states and cities.

    No one (politicians, business owners, scientists, parents, teacher) was ready for this and we are all bumbling along as best we can making mistakes daily. My governor is a mediocrity who vision is to copy the nearby states led by slightly less incompetent people. My city passed a hiring spree budget that is unchanged from the January proposal because there it is easier than trying to change things. An attempt to create a rainy day fund was voted down 14 to 2.

  7. A few comments:
    – Where I live (Indianapolis area) our hospital ICU beds and ventilators are available at normal, non-covid levels. The curve appears to have been flattened.
    – A vaccine may not even happen.
    – The statistics quoted at the end of the post suggest wearing masks in public as protection from brief walk-by encounters is pretty pointless.

    Obviously some immunity develops when a patient recovers, but the duration of that immunity is unknown. Our only viable option would seems to encourage “herd immunity” (ala Sweden) while individuals with risk factors self-isolate until Covid-19 levels drop to acceptable levels. Self-isolation for the whole country brings crushing economic hardship to hundreds of millions.

    1. I wouldn’t say wearing a mask is pointless. I would say not wearing a mask shows complete disregard for others. You have no idea if you’re asymptomatic or not. This report
      from the National Institute of Diabetes and Digestive and Kidney Diseases and the University of Pennsylvania, which was published yesterday in the Proceedings of the National Academy of Sciences, a peer-reviewed journal, shows that human speech generates droplets that linger in the air for more than 8 minutes. Anyone out there talking should be wearing a mask.

      1. Thank you for this reference! An excellent study that highlights the potential risk of viral transmission just from talking.

        However, the paper didn’t address the question of the infectious dose. The paper states, “The independent action hypothesis (IAH) states that each virion has an equal, nonzero probability of causing and infection,” and later on that the IAH likely applies to COVID-19. However, we still don’t know what that “nonzero” probability is. It very well may be quite small. In fact, given the transmission data from the contact tracing studies I cited in my article, and the fact that asymptomatic transmission is low to start with and 1/10th as likely as transmission from a mildly symptomatic patient, that nonzero probability is likely quite small for an individual virion.

        Second, I do think the added protection of wearing masks while out in public and passing by others only briefly (non-sustained casual contact) is negligible. The power of masks really comes into play during prolonged contact in closed spaces (while people are talking, as this paper argues).

        1. One of the positives of wearing a mask is not stressed enough; true, wearing a mask will lower the chance (other things being equal) of you infecting others directly by talking -let alone coughing or sneezing- , but it also reduces your chances of infecting surfaces, surfaces which we touch with our hands, hands with which we touch our faces, often unconsciously.
          Masks are most effective if everybody wears them.

    2. Yes, I understand that most governments are working on the basis of reducing the rate of infections to manageable levels, rather than eradicating the virus. That is saying that economics takes preference over peoples health. But the U.S. government in general seems to have taken that to another level, with the rate of infections being unlike that of any other country.

  8. Complete common sense. People have been over-estimating the risk of contracting the virus through surface contact. There is a negligible risk that you’ll catch it off a packing box, for instance. A visit to a nursing home is another matter.

  9. Thanks for this. I’ve no questions for the doctor only the observation that the “bad news” about a vaccine is really just uncertainty. Yes, we have no effective vaccine against HIV, but retroviruses are a horse of a different color. It’s true that a vaccine can induce overactive (and potentially very dangerous) so called “cytokine storms” and they are one culprit in the high mortality rate in COVID-19 patients, especially among the elderly. But we don’t know if any vaccine to SARS-CoV2 would do this and we don’t know yet if any such cellular response can be mediated.

    I guess I’m saying, it’s not so much bad news as we just don’t know. I find some comfort in a recent paper* which showed that almost everyone in the study who had confirmed COVID-19, sero-converted. This, combined with the report cited by Dr. Lickerman, suggests that we are at least able to mount a humoral response to the virus. Is it neutralizing? Is it durable? We don’t know. But it appears we CAN make antibodies to the virus.

    If what we don’t know is bad news, then what about what we do know?


  10. Very good, informative post that business owners would do well to read as they ponder their options.

    Question: with infectious diseases that confer some degree of temporary immunity after recovery, is the duration of that immunity relatively fixed? What I’m mostly wondering about is, if an individual is periodically exposed to a disease after recovering themselves, would that exposure stimulate continued antibody production beyond the “normal” timeframe?

    I’d imagine this could vary from illness to illness.

  11. Dr Lickerman, with the public now educated re pandemic precautions and healthcare facilities beefed up, could the curve be heightened some (re-open more businesses) to shorten the epidemic?
    Also, do we have a sense yet whether this viral infection has a natural cycle, like infuenza’s seasonal cycle.

    1. The short answer is, I think, yes. Flattening the curve was never about preventing cases; it was and is about delaying cases so the healthcare system is never at any point in time overwhelmed and a COVID-19 patient who needs a ventilator gets denied one.

      The low rates of transmission we’re seeing in the contact tracing studies I wrote about suggest to me that we could start to reopen businesses without the curve peaking beyond the capacity of the healthcare system to handle. A statistician/epidemiologist needs to model that.

      But for that to work, something else has to change: our culture. Getting everyone to consistently comply with social distancing measures (i.e., staying more than 6 feet apart, wearing masks throughout the day, not coming to work sick) I think will be really challenging. Each business will need a plan and an overseer of that plan who monitors compliance to make this work safely. It’s that challenge of changing culture that worries me.

      1. Yes, there cannot possibly a stronger argument in favour of mandated paid sick leave, I’d say.

  12. “Sadly, funding dried up just as researchers were about to proceed to clinical trials in humans”.
    Doesn’t give much hope for humanity’s ability to make strategic, fact-based, decisions. It would be like starting to build a rocket for countering a possible Earthbound asteroid, and then letting the funding dry up just as a giant rock came in to destroyed life on the planet. Anti-science in inhumane.

  13. It seems to me that the low % of infection figures that are quoted become high %s when you factor in that a transmitting person who works with other people, or commutes and so on comes into casual contact with dozens of people or more. That means that someones‘ gonna catch it. And that someone is going to spread it themselves later on.

    1. Depends on that person’s behavior. The risk of transmitting it to any one of those people such an index patient comes in contact with isn’t additive. And the risk of transmission from casual contact is even lower than the rates I quoted. But yes, even low rates of transmission results in new cases. Not that it’s inevitable each case will spread to others. Again, it’s about that index case’s behavior.

  14. “To deliberately infect volunteers who’ve been vaccinated against SARS-CoV-2 to see if they’re immune would be unethical …”

    Not necessarily, presuming the volunteers are young, healthy adults. There’s some risk with this, yes, but also a case for doing it based on potential lives saved versus potential lives lost.

    1. I agree. Police and firefighters often put their lives at risk to save others. I think a calculated risk is acceptable, if the volunteers are aware of the dangers. And they should definitely receive some kind of compensation for putting themselves on the line.

  15. I know that I must not touch a surface and then touch my face. What I don’t know is how those nasty little viruses get from my cheek to my nose. Obviously if I touch a surface and then rub my eyes or scratch my nose I’m in danger. But just touching my cheek?

    I get that eyes, nose and mouth are the vulnerable places. But what about ears? I do get that those invasive little buggers are only too happy to land on mucus-y surfaces. But I don’t know how wide open my ears are.

    1. We advise people not to touch their faces to prevent them from touching the points of entry of the virus, nose, mouth, and eyes. Ears and skin aren’t vulnerable. But when you don’t realize you’ve touched your ear or your cheek and then touch your nose, mouth, or eyes…

  16. A couple of weeks ago I noticed that, here in the UK at least, the phrase “asymptomatic carriers” had mutated into “asymptomatic and pre-symptomatic carriers” – I’m not sure how helpful the distinction is.

    My lack of understanding concerns how such carriers shed the virus if they don’t have a cough, sneeze, runny nose etc. Presumably by face-to-hand contact, but do they do it less efficiently in the absence of symptoms since they don’t cough/sneeze onto their hands?

    1. It now appears as if most people are most infectious right before they develop symptoms (if they do at all) and right after, with a spread of about 7-10 days of infectiousness. Asymptomatic people can spread the disease by 1) coughing or sneezing from another cause and sending viral particles from their mostly asymptomatic mouths/noses into the air, 2) talking, singing, etc. for a long(er) period of time in a confined space with others, 3) transferring virus onto surfaces as fomites that others then pick up and infect themselves with, 4) touching others directly. Asymptomatic spread, as mentioned in my article, is far less common than symptomatic spread, but is obviously still happening.

  17. I have to say wearing a mask makes me face-conscious and keeps me from touching.

    And it occurred to me that with all this virus avoidance we might not get as many colds…

    1. Not to mention TB, which is not much of a problem in the US I guess, but it is in South Africa.

  18. I read an article recently about several apparently healthy people in their 30s and 40s who suffered strokes after contracting COVID-19. Statistically, how common is this? How concerned should we be?

  19. Interesting that the rallying cry is always “Give us back our freedom or the economy will collapse” instead of “Give us our goddamn stimulus checks each month until the experts tell us it is ok to re-open our businesses and go back to our high-phyical-proximity jobs … or the economy will collapse”. What is needed is enough money in circulation so people don’t lose their homes or their ability to buy food and essential medicines. Absent that, people will die of starvation and/or medical neglect and the economy will die because of collapse of demand for goods and services. Giving handouts to churches and mega-corporations does nothing to help everyone survive the pandemic.

    1. Those people working shoulder to shoulder as eg. in the meat industry, should get proper PPE, a N95 mask appears a minimum there.

  20. There is also some advice for those not in stable relationships, but still have sex (human nature and all that). Do not only wear a condom, but also a mask (an N95 if you have access), and do it only doggy style. Maybe you’ll say that if it is like that it is not worth the trouble anymore, but it still is good advice.

  21. Dr Alex, IIRC there is quite a predominance of male victims. Is there any explanation that is a bit more than speculative there?

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