It's booster time — and time for FDA and CDC to keep up with the science

Many adults are having experiences like this one: You went to an indoor gathering last week, showed your vaccine card to gain admission — and partied like it’s 2019, assuming you were protected from a virus that mostly infects the unvaccinated.

Yet, six days later, feeling a bit under the weather, you got yourself a home test and — surprise — you got COVID-19! After spending the next half-day painstakingly trying to figure out everyone you spent time with to inform them that they were exposed, and after coming to terms with the reality that you — even as a healthy adult, say 35-years-old —will likely feel miserable for weeks. You’ll have to cancel your trip to Europe, and possibly discover what it means to have long COVID, you ask yourself: How did this happen? I was vaccinated!

But, actually, you were only kind of vaccinated. And not the useful kind in the middle of a pandemic, with an aggressive virus that spreads asymptomatically. Say, you got vaccinated in April. It’s been seven months. You did have a few months of solid protection, but your circulating antibody levels got very low, and you lost your immediate-early immune response. You needed a booster. But Food and Drug Administration (FDA) failed to authorize your booster, while Centers for Disease Control and Prevention (CDC) failed to recommend your booster. Your city and state may have failed to update vaccine requirements. The medical community failed to explain to you why you needed a booster.


Why is this happening? We get many vaccines to protect us against many diseases, yet we don’t have to get twice-yearly boosters for those. What is so special about COVID-19? First, this virus is everywhere right now. We’re not in a rampant pandemic of the other diseases you’re vaccinated against, but we’re in a rampant pandemic of this one. This means your chances of getting exposed to COVID-19 are much higher than other diseases. Second, the virus is commonly spread asymptomatically. That’s not the way we typically think of respiratory viruses, but it’s a big deal. It means that those six days after you got COVID-19 at that indoor gathering, you were shedding virus and putting your family, friends and coworkers at risk, all unbeknownst to you or them – in the same way that the person at the indoor gathering you attended probably spread COVID-19 to you.

Third, this virus is aggressive. Just a few minutes of unprotected exposure can spread the virus, even among people with perfectly healthy immune systems. 

All of this means that you need your immediate-early immune response. You need the antibodies that your immune system produced prolifically within a few weeks of your vaccination. Antibodies are what we measured in transplant patients and other immunocompromised people that showed us they needed third doses, which the FDA approved in August. Antibodies can quickly kill viruses before they start replicating, spreading asymptomatically, and causing trouble. Antibodies give you protection from breakthrough infections. Low antibodies mean low protection. In populations who don’t mount good antibody responses, risks of severe breakthrough infections are 485 times higher. So, it’s really no surprise that you, whose antibodies had substantially waned after initial vaccination, got COVID-19. 

But what about T cells? What about memory B cells? Immunity is supposed to be complex and long-lasting, and most other vaccines depend on this long-lasting immunity. This is all true. But, unlike antibodies that float around in mass numbers in your blood, ready to attack on command, T cells and memory B cells need to be activated, and to multiply, and to make new antibodies, which can take days to weeks. During a pandemic, with an aggressive virus that can spread asymptomatically, T cells and memory B cells are too slow, and not enough. They will likely keep you from getting hospitalized or dying, but they alone will not keep you from spreading the disease for days before you even know you have it, and they alone will probably not keep you from getting sick to some extent. During a pandemic, with an aggressive virus that can spread asymptomatically, you need antibodies as that first line of defense.

For months, we’ve known that antibody levels wane after vaccination. For months, we’ve known that vaccine efficacy wanes over time. And for months, we’ve known that boosters drastically reduce infections. In September, an Israeli study of over 1 million fully vaccinated people (two-doses) reported that the rate of confirmed infection was lower among those who received a booster by a factor of 11.3, and the rate of severe illness was lower by a factor of 19.5. These striking findings suggest that the difference between a boosted-vaccinated person versus an unboosted-vaccinated person is similar to the difference between a newly vaccinated person versus an unvaccinated person.


In other words, boosted is the new vaccinated and unboosted is the new unvaccinated.

Of 125 million Americans who are six or more months out from full vaccination, only 32 million have received a booster. The rest are at higher risk than they should be. Perhaps this is because of the confusing, constantly changing, county-and state-level patchwork of rules about eligibility, even though boosters seem to be incredibly safe and there seems to be plenty of boosters available. Or perhaps this is because CDC hasn't given anyone any reason to get boosted: a guidance that reflects how much safer it is to be boosted would help to explain and motivate boosters — and also to remind people that, without boosting, many activities aren't going to be as safe during the upcoming holidays as they were in June.

It’s time for FDA to authorize your booster. It’s time for CDC to recommend your booster. And it’s time to realize that those who have been recently vaccinated, recently infected or recently boosted are likely much more protected than those who are more than six months out from vaccination.

Dorry Segev, MD, Ph.D., is a professor of surgery at Johns Hopkins University School of Medicine and Professor of Epidemiology at Johns Hopkins Bloomberg School of Public Health. Segev has been leading an observational study of COVID-19 vaccine responses in immunosuppressed people since December 2020 and is the principal investigator of the NIH/NIAID-funded interventional trial "COVID-19 Protection After Transplantation (CPAT)." Follow him on Twitter: @dorry_segev