Category: pandemic

More evidence that COVID-19 had a zoonotic (animal) origin and didn’t come from a lab

August 19, 2021 • 10:30 am

“Zoonotic,” in case you didn’t know, refers to an infectious disease transmitted between animals. And, in a post a few days ago, I highlighted a paper in Science suggesting that the coronavirus did originate as a zoonotic disease: it came from horseshoe bats and was transferred by bats to another mammal (one likely candidate is the palm civet or “civet cat”, a viverrid, not a felid), and then from this mammalian carrier to humans in Wuhan “wet markets.” The authors emphasized that there was no evidence that the virus came out of the local lab.

A new paper in press in Cell comes to the same conclusion, though they summarize all the evidence, not just the phylogenetic evidence (family tree of viruses). The new paper, however, is not as certain about the species of mammal that transferred the virus from bat to human. But they are pretty sure that the virus was not cultured in the Wuhan Institute of Virology (WIV), and then either escaped or was somehow released to cause disease. This paper, which Matthew called to my attention, has an international team of distinguished disease experts as authors, and they summarize all the evidence that COVID-19 is a purely zoonotic disease and escaped from a Wuhan wet market, not from the WIV. The paper is really only 11 pages long, and you can download the pdf by clicking on the screenshot below.

I’ll just summarize the lines of evidence (there’s more in the paper, too, but the first 11 pages of double-spaced text is all you need to read.

1.) All previous coronavirus infections of humans (viruses other than SARS-CoV2, or what I’ll call COVID-19) have a zoonotic origin, several of which had their origin in “wet markets” selling animals like civet cats and raccoon dogs. Workers in these markets have high concentrations of antibodies against various coronaviruses.

2.) The sequence of COVID-19 is similar to that of other coronaviruses in humans known to have zoonotic origins.

3.) Epidemiologically, the spread of the virus strongly implicates the wet market in Wuhan as the source, not the WIV.  As the authors note:

Based on epidemiological data, the Huanan market in Wuhan was an early and major epicenter of SARS-CoV-2 infection. Two of the three earliest documented COVID-19 cases were directly linked to this market selling wild animals, as were 28% of all cases reported in December 2019 (WHO, 2021). Overall, 55% of cases during December 2019 had an exposure to either the Huanan or other markets in Wuhan, with these cases more prevalent in the first half of that month (WHO, 2021). Examination of the locations of early cases shows that most cluster around the Huanan market, located north of the Yangtze river (Figure 1B-E), although case reporting may be subject to sampling biases reflecting the density and age structure of the population in central Wuhan, and exact location of some early cases is uncertain. These districts were also the first to exhibit excess pneumonia deaths in January 2020 (Figure 1F-H), a metric that is less susceptible to the potential biases associated with case reporting. There is no epidemiological link to any other locality in Wuhan, including the Wuhan Institute of Virology (WIV) located south of the Yangtze and the subject of considerable speculation. Although some early cases do not have a direct epidemiological link to a market (WHO, 2021), this is expected given high rates of asymptomatic transmission and undocumented secondary transmission events, and was similarly observed in early SARS-CoV cases in Foshan (Xu et al., 2004).

If you’re a conspiracy theorist that the virus was released from the lab by mistake, you’d have to say that it somehow got itself over to the wet market before it started infecting people. The wet market, not the WIV, was the epicenter of the infection.

4.) The COVID-19 virus was actually detected in “environmental samples” taken in the Hunan wet market, especially in the part of the market that sold animals and animal parts.

5.) As I showed in my post two days ago, the viruses closest in sequence to the human COVID-19 virus are three bat viruses from Yunnan. (It’s still not clear how they or their relatives found their way to the Yunnan wet market). But the telling part is, as the authors say, “None of these three closer viruses were collected by the WIV and all were sequenced after the pandemic had begun.”

6.) The absence of the known intermediate animal host for COVID-19 does not suggest that the virus was clearly engineered by humans in the lab, for the animal source of many human pathogens of zoonotic origin, including Hepatitis-C, polio, and Ebola, have not been identified.

7.) Although there have been isolated incidents in labs in which people got infected with viruses, there’s been only one documented example of a pandemic coming from human origin: “the 1977 A/H1N1 flu epidemic, that most likely originated from a large-scale vaccine challenge trial.” There are no epidemics known caused by the escape of a novel virus. (You might respond that, “Well, this could be the first one,” but the other evidence I adduce tells against this.)

8.) There is no evidence that the WIV or any other lab was working on the SARS-CoV-2 virus or any related virus before the pandemic.

9.) Despite extensive attempts to find the virus in workers at the WIV, there are no reports of COVID-19 infections in that institute.

10.) Previous experimental work on coronaviruses at the WIV have involved inserting a “genetic backbone” and other genetic markers that we do not see in the human COVID-19 virus that’s causing the pandemic.

11.) To culture the virus in the lab, workers would have to infect wild-type mice, but were unable to do so with SARS-CoV-2.  The virus has since been engineered to be culture-able in mice, but that occurred after the pandemic had already begun.

12.) Adaptive mutations that enhanced the infectivity of the virus arose after the pandemic started, ergo were not engineered in the lab.

13.) Sequences that “lab-contaminant” advocates say could only have been engineered into the virus by humans have in fact been found naturally in other coronaviruses. That they’re missing in close relatives of the coronavirus could reflect only our pretty profound ignorance of what strains SARS-CoV-2 evolved from from.  And there is no evidence that that kind of genetic engineering was ever going on at WIV.

The “conclusions” on pp. 10-11 are pretty clear:

“the most parsimonious explanation for the origin of SARS-CoV-2 is a zoonotic event” involving transfer from an intermediate host in a Wuhan wet market.

“There is currently no evidence that SARS-CoV-2 has a laboratory origin.”

And the last paragraph:

We contend that although the animal reservoir for SARS-CoV-2 has not been identified and the key species may not have been tested, in contrast to other scenarios there is substantial body of scientific evidence supporting a zoonotic origin. While the possibility of a laboratory accident cannot be entirely dismissed, and may be near impossible to falsify, this conduit for emergence is highly unlikely relative to the numerous and repeated human-animal contacts that occur routinely in the wildlife trade. Failure to comprehensively investigate the zoonotic origin through collaborative and carefully coordinated studies would leave the world vulnerable to future pandemics arising from the same human activities that have repeatedly put us on a collision course with novel viruses.

This paper is of course tentative, like all such conclusions, but the data add up to a “normal” zoonotic event and not escape from the lab. It’s clear the virus was not engineered to kill humans as a bioweapon, as there’s no evidence that the WIV worked on it. And even if it did, why would it happen to escape to a wet market—places where these viruses are known to exist naturally.  Nor is there evidence that the WIV was simply studying the virus and it escaped as an accident that caused the pandemic.

In other words, conspiracy theories about the virus seem to be untenable, but, humans being human and prone to conspiracies, they’ll persist.

UPDATE: in the thread after this tweet, third author Rasmussen goes through the evidence that people think supports a lab origin, and then dispels it:

h/t: Matthew

The origin of the coronavirus

August 17, 2021 • 1:00 pm

A new paper in Science (click on screenshot below, pdf here, reference at bottom) suggests that Covid-19—referred to in this study as SARS-CoV-2—likely originated in horseshoe bats that were collected in Yunnan in southern China, were not contaminations from the Wuhan Institute of Viriology (WIV), but were transferred to humans via an intermediate animal vector (probably a civet cat) in a wet market. Note that two of the authors are Chinese, and one might think that they have an interest in exculpating the WIV, but that opens up a whole can of worms that I’d prefer to avoid.

Click:

Here’s a phylogeny (family tree) of the “sarbecoviruses” that are evolutionarily closest to the Covid-19 virus, with the caption from the Science paper. Click on photo twice to make it really big.

Note that the three viruses closet to human coronavirus in sequence are all from areas close together in Yunnan, and all in species of horseshoe bats ( genus Rhinolophus, variants RpYN06, RmYN02, and PRC31). Viruses in pangolins (Manis javanica), also presumably derived from bats, are much less closely related, and thus unlikely as a source of human infection. The virus RaTG13, sequenced and kept at WIV, seems too distant from the human coronavirus to have been the source, and horseshoe bats are found not just in Yunnan, but are widely dispersed throughout China.

The authors posit that, since bats were not sold in Wuhan markets, another animal—they think the civet cat—is the likely transmitter of the virus to humans in a wet market, and this happened in about December of 2019. The bat virus may have gotten into a civet (or a raccoon dog, or a fox, or a mink) on one of the many farms where these animals are raised for sale as meat, and then transported to wet markets in other places in China.

As an interesting sidelight, the authors suggest that the spread of the coronavirus was promoted by a shortage of pork in China in 2019, which itself was due to swine flu that led to 150 million pigs being killed. They posit that other animals, like civet, could have replaced pork in the diet, and those animals would be intermediate vectors that led to the interspecies leap in late 2019. (Our own species is now considered the main vector for Covid-19!).  They suggest, alternatively, that the virus could have survived in frozen wild meat rather than in live animals sold in wet markets.

Finally, now that we’re the main host of the virus, the authors worry that we ourselves could infect other wildlife, which would then become reservoirs for evolution and re-infection (this is called “reverse zoonoisis”)

There are several questions that are unanswered in this short paper, but may be common knowledge. How do the authors manage to discount a lab strain as a source of the human infection? Were the closest Yunnan viruses not kept in the Wuhan Institute? Did anybody sample civets or other animals sold in the Wuhan market for coronavirus? (The market, of course, is closed, so this may be impossible.) Why do the authors consider the civet cat (palm civet) the most likely intermediate host of the virus? They cite this paper, showing a near-identity of the human and palm civet virus, but do they have similar data from other mammals?

I am not an expert on the various theories of transmission of cornavirus from bats (the most likely origin) to humans, but offer this for your delectation.

___________

Lytras, S., W. Xia, J. Hughes, X. Jiang, and D. L. Robertson. 2021. The animal origin of SARS-CoV-2. Science: DOI: 10.1126/science.abh0117

The latest from my doc on the pandemic, vaccinations, masks, and Delta

August 9, 2021 • 12:30 pm

My extremely competent and science-oriented physician, Dr. Alex Lickerman, has written post #14 in his continuing series about the coronavirus and the pandemic. It’s free, and you can read it by clicking on the screenshot below.

This one answers a number of questions that many of us have. I’ll give a precis of the answers at the end, but you need to read the whole thing. After all, immunized or not, it’s your health. I think you’ll find the answers reassuring.  And what I like about this post, as with the others, is that the answers are completely driven by data.  When the data are ambiguous or unclear, Alex lets us know.

Alex has volunteered to answer readers’ questions, so feel free to ask them in the comments section below.

Some of the questions asked and answered (or not answered if we don’t have data):

  • Is the Delta variant of cornavirus more contagious than other strains of the virus.
  • Does the Delta variant cause more severe disease than the other variants?
  • How effective are the vaccines against the Delta variant?
  • How much do we need to worry about “breakthrough infections?  Here I’ll quote something Alex notes:

But here’s the bottom line: the absolute risk of becoming infected to which vaccinated people are being exposed in most situations in which they find themselves will be far less than 7.2 to 28.8 percent.

This does explain, however, why breakthrough infections with Delta can and do occur. But what we care about most—and what the vaccines were really designed to mitigate—isn’t the risk of catching COVID-19. It’s the risk of being hospitalized and dying from it (as well as the risk of developing long-COVID). Here, the CDC data tells the real story: as of this writing (at a time when, as mentioned above, the Delta variant is the dominant strain infecting people in the U.S.), of 164 million people fully vaccinated (with a mix of the mRNA vaccines and the J&J vaccine), 5,285 people have been hospitalized for COVID-19 (which yields a risk of being hospitalized from severe COVID-19 if you’re immunized of 0.003 percent), and of those 1,191 died (which yields a risk of dying from COVID-19 if you’re immunized of 0.0007 percent). When you consider the risks most of us take every day without worrying about them at all—for example, over the course of a year, the odds of getting into a car accident are 3.7 percent on average and the odds of dying in a car accident are 0.3 percent, making the annual risk of dying from a car accident 0.01 percent, which is 14 times the risk of an immunized person dying from COVID-19—our inability to think statistically clearly has us afraid of the wrong things. (This goes for the decision to be vaccinated as well: our annual risk of dying from a car accident turns out also to be 14 times the risk of the most common serious adverse reaction to the vaccines—blood clots with the J&J vaccines—which occurs at the same rate as the rate of death from COVID-19 if you’re fully immunized, a rate of 0.0007 percent.)

  • Does immunity conferred by the vaccines wane over time? If so, at what rate?
  • Should we be looking to get “booster” (third) vaccinations?
  • Can fully vaccinated people spread the variant? If so, should vaccinated people mask up?
  • Is traveling safe now?

And I’ll give you a peek at the answers but, as I said, read the whole piece and then fire away with questions. A quote from the article:

CONCLUSION: It’s hard to know how to think about immunization, the Delta variant, and how we should behave in different circumstances to keep ourselves and those around us safe. We’re all seeing the science unfold in real time, revealing just how messy, uncertain, and difficult it is to figure out what’s really true. But, though it takes time, science ultimately gives us answers we can rely on. We can all argue about what policies make the most sense based on what the science shows, but it’s the science we should all use to help us guide our own behavior. And, as of this writing, the science says the following:

  1. The Delta variant is more contagious than other variants.

  2. The Delta variant may be more dangerous than other variants.

  3. The vaccines are likely somewhat less effective in preventing infection with the Delta variant, but still offer an enormous amount of protection. Breakthrough infections are occurring, but they are overwhelmingly mild.

  4. Vaccinated people probably can transmit the infection but almost certainly at a lower rate than unvaccinated people.

  5. The vaccines remain unbelievably effective at preventing hospitalization and death from the Delta variant, so much so that vaccinated people can continue to live as they did before the onset of the pandemic, with the possible exception of wearing masks to prevent asymptomatic spread to vulnerable people in areas of high prevalence of disease.

  6. A third booster shot for non-immunocompromised people doesn’t make sense at this point in the pandemic. Some people who are immunocompromised may want to consider a third shot.

Did the Covid-19 virus come from a Wuhan lab? It’s looking increasingly likely.

June 4, 2021 • 1:15 pm

You surely remember last year when the “conspiracy theory” was broached that the coronavirus, which was thought by nearly all the media to have come from a Wuhan wet market, might have actually come from a virology lab in Wuhan, with some even suggesting that it might have been released on purpose.

Well the “deliberate release” scenario is dumb, since how could one contain an easily-spread virus targeted at an enemy? But the “accidental release” theory is gaining more and more credibility, with the Biden administration deciding to launch its own investigation. The story below, from Newsweek (yes, a conservative site), recounts how a group of amateur Internet sleuths pieced together from publicly available data what is the most likely story: an accidental release of a virus stored in the Wuhan Institute of Virology (WIV). That virus seems to have come from a Chinese cave in which 3 men shoveling bat guano died in 2012, and died from a virus that was remarkably similar to the coronavirus responsible for the pandemic.

It’s thus likely that the Chinese repeatedly lied about the origins of the virus and the U.S. government, suckered in, didn’t do due diligence in following up. After all, if a bunch of amateurs can piece together this tale (and I emphasize that we don’t know if it’s true for sure), why couldn’t the government?

Click screenshot to read the story:

It was a group of amateurs, following the lead of an young Indian called “The Seeker,” who determined that the sequence of the pandemic virus was almost identical to that of the virus stored in the WIV (they managed to get the latter sequence), and that that virus was likely the one who killed the three men nine years ago. They also found out, through diligent labor, that the WIV was actually studying the virus despite their denial, and had made seven trips to the guano mine to collect samples. The amateurs found grant proposals from the WIV, which was apparently testing the infectivity of the collected viruses, possibly with the hope of producing a vaccine against them.

As Newsweek notes, “The ongoing effort to cover this up implies that something may have gone wrong.” What went wrong, if the story is indeed true, might never be known, as the Chinese either might not know themselves and at any rate haven’t been exactly forthcoming about what they do know. Now professional journalists and epidemiologists are on the case, so we should get some answers—at least about whether the virus came from the WIV.

The episode of course makes China look bad (the article is replete with the WIV’s and Chinese government’s lies), but it also makes the U.S. look bad. It makes the press look bad: newspapers and websites had to go back and change months-old headlines that the lab-escape theory had been debunked. And it makes science look bad. To dismiss a theory without having investigated it first, and dismiss it so, well, dismissively, is only going to make people trust scientists less.  It’s even worse when you realize that had the Chinese been open about what they were doing, and were studying the sequences of viruses related to the pandemic organism, a vaccination might have been developed—or at least been in the works years before the outbreak.

Again, this is just a theory, but it’s a theory that’s become so plausible that nobody dismisses it as lunacy any more, and our own government is taking it seriously. If it turns out to be true, what will be the upshot? We’ll know to trust Chinese assurances even less (apparently the U.S. government was too credulous), and perhaps this can ensure more cooperation with the Chinese in future cases. But I wouldn’t count on it. At least we know that science works best when it’s at its most open.

At any rate, you owe it to yourself to read this fascinating amateur detective story.

h/t: Luana

Effectiveness of coronavirus vaccines

May 2, 2021 • 11:00 am

My doctor, Alex Lickerman, has put up post #13 in his continuing series on the medical science of coronavirus and the pandemic. This short but informative post (click on screenshot below) deals with a question we all have:

First, the effectiveness. Alex summarizes numerous studies showing how effective a vaccine is. Remember, though, what that number, expressed as a percentage, means. If a vaccine is 95% effective, it means that in a situation in which a certain percentage of people get infected, say 30%, then the chance you will get in infected is (100% – 95%) X 30%, or 1.7%.  Note that this does not mean that your chance of getting infected is 5%: it’s lower than that because not everybody gets infected when they’re not vaccinated.

Here are some effectiveness estimates taken by Alex from the literature:

Single dose Pfizer: 70%
Double dose Pfizer: 85%
Single dose Pfizer and Modern considered together, single dose: 80%
Double dose   ”            ”                   ”                 ”            double dose: 90%
The two above figures are also the same in another study not specifying vaccination

The 80%-90% holds for both symptomatic and asymptomatic infections; this means that yes, you can be an asymptomatic carrier if you have been fully vaccinated, but the chances are very small.

 Pfizer and Moderna combined (both mRNA vaccines): effectiveness: over 96%

Now remember again what these figures mean, because people get that meaning wrong all the time. Here’s one example I quote from the article:

A CNN article was skeptical of this data, arguing that “real-world studies of the Pfizer-BioNTech and Moderna vaccines show they are only 90% protective against the coronavirus, not 95% as reported in clinical trials. Translated into reality, that means for every million fully vaccinated people who fly, some 100,000 could still become infected.” Importantly, this is not what 90 percent effectiveness means! Ninety percent effectiveness means the vaccines reduce the rate of infection by 90%. To calculate a person’s absolute risk of getting infected after having been vaccinated, you have to start with the base rate of infection, which is different in different contexts. It would be true that “for every million fully vaccinated people who fly, some 100,000 could still become infected” if the base rate of infection for those million people was 100 percent. Yet the highest rate of infection we’ve seen in published contact tracing studies was around 30 percent (for spouses of infected people). This means that post-vaccination rates of COVID-19 infection in the vaccinated population are at most 90 percent less than 30 percent, or 3 percent. And that only if everyone who’s been vaccinated has an infected spouse.

In fact, the CDC reported that, as of April 20, 2021, out of 87 million fully vaccinated people there were only 7,157 breakthrough infections (0.008 percent), only 498 hospitalizations (0.0006 percent) related to COVID-19, and only 88 deaths (0.0001 percent) related to COVID-19.

Alex’s bottom line:

The mRNA vaccines are extraordinarily effective at preventing both symptomatic and asymptomatic infection and therefore at preventing transmission of SARS-CoV-2. Most importantly, if you’re fully vaccinated, your risk of dying from COVID-19 is 0.0001 percent.

What about the variants?. In answer to the question of whether the vaccines work against the variants, Alex says “yes”, at least for variants currently circulating. He adds that more data are to come.

Here’s Alex’s conclusion, which happens to echo the same conclusions reached by Bari Weiss in a piece published on her site this morning:

CONCLUSION: Given the incredible effectiveness of the vaccines at preventing both symptomatic and asymptomatic disease, and therefore disease transmission, and given that the rates of death from COVID-19 in vaccinated people is 0.0001 percent among all vaccinated people in the U.S. (an analysis that also included the J&J vaccine), if you’ve been vaccinated, we consider it reasonably safe to dine indoors, travel, and gather with even unvaccinated people. Living in the world has, of course, never been risk-free. Yet we can now say that with the advent of effective vaccines against SARS-CoV-2, the risk of living as you did before the pandemic has returned to what it was before the pandemic.

Here’s Weiss’s piece, which I think is free, though I’ve now subscribed. Click on the screenshot:

New post by Dr. Alex Lickerman: Should you get the Johnson & Johnson vaccine?

April 2, 2021 • 10:00 am

Dr. Alex Lickerman, my GP, has a new post on his website about the coronavirus and vaccines, the twelfth since he began posting during the pandemic. Click on the screenshot below to read it (it’s free).

The short answer to the title question is “yes”, but there are lots of other questions answered (and some raised without known answers). One is whether you can be an asymptomatic carrier if you’ve been vaccinated. Alex’s answer:

The study didn’t present enough data to prove the vaccine prevents asymptomatic infection. Nor did it assess whether subjects who developed COVID-19 despite vaccination are less likely to transmit the virus. Thus, it’s not yet clear how effective the vaccine will be in containing the spread of the infection. (A recent study from the CDC, however, strongly suggests that both mRNA vaccines—Pfizer’s and Moderna’s—do indeed prevent even asymptomatic COVID-19 infection by 90 percent in real-world circumstances, which is great news. We need more studies to learn if this is also the case for J & J’s vaccine.)

Summary paper on the vaccines with Fauci as senior author

January 20, 2021 • 10:45 am

Reader Simon sent me a link to this free paper about coronavirus vaccines written by several researchers, including Anthony Fauci (“senior author” means “last author”, and the convention that this spot is occupied by the Boss or lab head). It’s a useful summary of where we are, which other vaccines are coming, and what we don’t know, and is understandable by the layperson. (Here’s a link to one term you might not know: “mucosal immunity“, while “parenterally” refers to medicines taken outside the digestive tract, usually through injection.)

Click on the screenshot to read:

There’s a useful table of vaccines already used compared to those in development. Of the five remaining vaccines, three involve viruses: mostly inactivated viruses that can’t replicate but can produce the spike protein that activates your antibodies, while two others involve injecting spike proteins themselves, made in insect cells. Click to enlarge:

 

Here’s a figure I’ve posted before showing the protection you get from the two vaccines in use in America now: the Pfizer/BioNTech and Moderna formulations.

Note that you’ve already gotten substantial protection before you get to the second jab. For both vaccines the efficacy (the reduction in the chance you’ll catch the virus if exposed) is about 95%.

The paper raises several concerns about the vaccines and people’s willingness to take them.

A.)  What are the side effects? Monitoring of those injected has only taken place for several months, and there may be long-term effects we don’t know about. The authors note, though, that some of the vaccinated would have had stuff like cancer and heart attacks anyway—effects having nothing to do with the injection. The frequencies of such incidents and diseases need to be compared to those in unvaccinated groups or base rates already known.

B.) We don’t know the efficacy in some important groups, including “children, pregnant women, individuals with underlying illnesses, and those taking medications that might influence the immune response to a disease.”

C.) The duration of protection provided by the vaccines. We know that the efficacy of flu vaccines wanes substantially between six months and a year after injection. Will we have to get yearly injections of coronavirus vaccines as we do with flu shots?  Of course they will continue developing vaccines, so they will get better over time.

D.) How well do the vaccines protect against (asymptomatic) infection and transmission of the virus? We should have the answer to this question in a while, and the authors consider this the most important unknown in trying to stem the pandemic. If after injection you can get infected and not show symptoms, as well as transmit the virus, this will dramatically curtail efforts to stop the pandemic cold, and mandate different strategies, like testing those already injected.

And a paragraph from the paper, which is disturbing given that roughly half of Americans plan to get vaccinated. That is INSANE! Tell your worried friends to get their jabs, as it’s better than getting coronavirus.

The point made is that the vaccines currently in use don’t provide immunity in the mucosal membranes (as in the nose), while polio vaccine did bestow that immunity, but only if made with live weakened virus. (Current flu vaccines don’t provide it either.) Active immunity in the mucosa kills the virus in the respiratory system before it has a chance to get into the blood. The coronavirus vaccines now available don’t seem to provide mucosal immunity and, as the authors say, we need vaccines that will do that. A summary:

Given that recent polling suggests that only 40% to 60% of people in the United States are currently planning to get vaccinated, it is conceivable that without some impact on transmission, the virus will continue to circulate, infect, and cause serious disease in certain segments of the unvaccinated population. Administration of parenterally administered vaccines alone typically does not result in potent mucosal immunity that might interrupt infection or transmission. In the case of poliovirus, induction of mucosal immunity through vaccination with the live attenuated oral polio vaccine, in contrast to the parenterally administered inactivated vaccine, was thought to have played a critical role in interruption of transmission and control of poliovirus epidemics. For these reasons, additional data regarding protection from infection should be generated as soon as possible. If these vaccines do not provide durable, high levels of protection from infection, and do not drive the prevalence of virus in the community to near zero, a thorough analysis of shedding and transmission will need to be done through additional study. Armed with such data, public health officials can make decisions regarding prioritization of populations to receive the vaccine, and researchers could potentially improve upon the first wave of vaccines.