Vinay Prasad, MD, MPH, hematologist-oncologist and associate professor of medicine at the University of California San Francisco. 2021.01.19
Recently, a spirited discussion was sparked on social media: is it acceptable to relax masking 14 days after the second COVID-19 vaccine dose? Having spent some time thinking about the topic, and discussing with colleagues, I have reached two conclusions. First, it is a tradeoff with residual uncertainties, and reasonable people can disagree. But also, I favor the view that generally, 14 days after vaccination, we can relax some restrictions.
It is important to be upfront with the caveats. Everything I say applies to average people in the community — I am not speaking about enhanced precautions in high-risk settings like nursing homes or medical centers. My argument is contingent on there being no “vaccine escape,” that is, no mutation in the coronavirus that markedly reduces vaccine efficacy. If that happens, may God help us. I am not sure we will make it.
Finally, my argument is appropriate for most places and most times, but if health systems are overwhelmed, e.g., as we saw in places like southern California or New York City, it might be reasonable to temporarily increase precautions. Additionally, my guiding principle does not apply to businesses, such as grocery stores or pharmacies, which can and will enforce their own policies.
Now, having said that: for most people, once you get 14 days out of your second dose of vaccine, I believe you can ease up on masking or another restriction, such as visiting a loved one for lunch or having more than one person visit a nursing home at the same time, or a small gathering of vaccinated people for dinner without masks.
There are three lines of evidence that I wish to offer for my claim. First, consider the efficacy of the vaccine. The efficacy of the two mRNA vaccines is superb, offering 95% reduction in the rate of acquisition of symptomatic COVID-19 in randomized trials. That is a remarkable result. But the key statistic here is one step beyond the vaccine efficacy. If you get two doses of the vaccine, and if you remain asymptomatic 14 days after the second dose, what is the probability you will develop COVID-19? For Moderna, the answer is there is a 99.92% chance that you won’t. Only 12 cases occurred after this time in 14,550 actively vaccinated people in the trial, while the control arm experienced nearly 3.5% cumulative incidence. For Pfizer, only eight cases occurred amongst people who had completed a second dose and went 7 days without symptoms, again a 99.95% chance of not getting COVID if one remained asymptomatic a week after the second dose. In other words, if you get 14 days past the second dose, and feel fine, the likelihood you will get COVID-19 in these studies is very low. Some argue that in the real world — where folks are not as motivated as trial participants — the rate of SARS-CoV-2 acquisition might be higher, and thus relaxing rules riskier. But this logic cuts both ways: if people in the real world are less compliant, then the rules might be relaxed no matter what we say.
Next, consider the risk of spreading SARS-CoV-2 to others. That risk is in part driven by symptomatic infections which are exceedingly rare after second doses. Risk of spreading is diminished by the brisk immune response that occurs after symptomatic infection once someone is vaccinated. In the Moderna study, there were 30 cases of severe COVID overall and zero in the vaccination arm. Less symptomatic and less severe COVID will result in a lower propensity to propagate SARS-CoV-2. Moreover, studies of both recombinant antibody products speed viral clearance from airways. If the body is primed to manufacture anti-spike antibodies through vaccination, there is likely a similar rapid clearance and subsequent reduction in infectiousness occurs.
What about asymptomatic infection and so-called silent spread? In the Moderna trial, swabs taken from asymptomatic participants as they were receiving dose 2 showed a roughly 60% reduction in PCR positivity. It is likely that a second dose and longer asymptomatic period will result in greater reduction in PCR positivity. Preliminary data from AstraZeneca’s ChAdOx1 vaccine also showed reduced in asymptomatic PCR detection. In short, it is highly likely that receipt of vaccination and a 14-day asymptomatic period afterward results in both personal protection and reduced likelihood of ongoing viral propagation.
Third, what is the effect size of masks? More correctly — what is the effect size of masks 14 days after a vaccine with 95% efficacy? What is the effect of masks if PCR positivity is only 1 in 1,000 amongst asymptomatic people? I think we must confront a forgotten truth. Masks make sense not because we have perfect randomized controlled trial data showing they protect the wearer, or others, but based on bio-plausibility, and the precautionary principle, they were a reasonable public health measure to incorporate.
Authors of a 2020 update to the Cochrane review wrote, “Compared to no masks there was no reduction of influenza-like illness (ILI) cases (risk ratio 0.93, 95% CI 0.83-1.05) or influenza (risk ratio 0.84, 95% CI 0.61-1.17) for masks in the general population, nor in healthcare workers (risk ratio 0.37, 95% CI 0.05-2.50).” But the truth is none of these trials perfectly fits the moment. And we never did a cluster RCT of cloth masks — as they are used in the politically torn U.S. — to clarify the effect size with SARS-CoV-2.
The truth is I wear a cloth mask and I quite like it. But I have seen no data that can tell me the added benefit of masks 14 days after vaccination with 95% efficacy. It’s the biological equivalent of asking what happened before the Big Bang. If you ask, what is the evidence that it’s safe to stop wearing a mask, I say, what is the evidence that it’s still beneficial?
This same line of thinking applies to other restrictions that could be eased instead. What evidence supports restricting nursing home visitors, if all parties are vaccinated and masked? What evidence supports banning a small dinner, if everyone has had the vaccine? There is no evidence that supports these continued prohibitions.
Knowing these three facts allows us to put it all together. Is it reasonable to tell someone that, if they are asymptomatic 14 days after the second vaccine, they are highly unlikely to get COVID-19, and also less likely to spread the virus — both by having less severe disease, less asymptomatic carriage, clearing virus faster, stronger antibody responses, and fewer symptomatic cases? Absolutely, is my view.
It is then reasonable to say that the theoretical benefit of the mask may be so small that easing up on its use is fine. Alternatively, you might keep the mask, but ease up on something else, and, to be honest, most people might actually prefer a different concession. You might choose to see family instead, or have a gathering with your vaccinated friends. Getting vaccinated is like getting a stack of tickets at Chuck E. Cheese — you get to decide what to trade them in for!
Some contend my stance will undermine efforts to normalize masks, send mixed messages to the public. That’s possible, but it is also possible that my message empowers and excites people to get vaccinated, which is the only viable path out of the nightmare we find ourselves in. I think the less scientists manipulate their statements while trying to guess the response the better. I have tried to be fully transparent in my thinking on this topic. None of us knows the second or third order effects. If we distort the facts and bang on harder about prolonged mask use or other restrictions, will the world actually be better? Or will we provoke a deep backlash that has been brewing for some time? Do we risk losing some folks who might otherwise get vaccinated? I am not an incarnation of God, so I don’t know. I worry that the likes and retweets on social media encourage the fearful message rather than the correct one.
Public health experts have reminded me to talk about despair. We are all facing it, and when you clamp down on a society with restrictions, a free society can only bear it for so long. There must be a path out of it, and easing restrictions — particularly when the burden may outweigh the unproven, theoretical, and at best highly marginal benefit — is a great way to renew optimism. Folks who spend time doing boots on the ground public health share their view with me that this is a great place to start.
The last objection I want to discuss is that my policy is not the safest policy. It is not absolute safety. Indeed, I acknowledge this is true. But I disagree that wearing a mask is absolute safety. I disagree that only one nursing home visitor is the safest policy, and only having a picnic outside is safest. Only truly becoming a hermit is absolute safety. Lock yourself in home, and get all foodstuffs delivered. When you go out, always wear an N95, and do this even a year or two after vaccination. After all, who knows if the vaccine will wear off? None of us really wants absolute safety. We seek reasonable safety, and I will defend the proposition that is achieved merely by a prolonged asymptomatic period after second vaccination and after that something can be relaxed — and there are several options.
The end of COVID
COVID-19 will someday no longer be the topic of daily and breathless news coverage. The virus may always circulate, and some people may always get sick, but the real end will be when we stop thinking about it every moment of every day. That’s how this pandemic will end. Not with a bang, but a whimper.
People need to know that there is light at the end of the tunnel because there is.
Vaccination in the absence of viral escape is the way out of this. Once a person is a sufficient time and distance away from the second shot, and if they are feeling well, we can start to view them differently. They are less a vector for the transmission of a plague, and more a real person — with hopes and wants and desires and seeking connection. In such a moment, if they remove their mask to share a smile with me, I can promise you, I will lower my mask, and smile back.