WHAT the heck is going on with booster shots?!


A: Booster doses are coming soon for older adults in the U.S. and U.K who are 6 months past their 2nd dose.

If you’re having a hard time keeping up with the data and discussion around 3rd doses or booster shots of the COVID-19 vaccines, you’re not alone! (And what’s the differences between a booster and 3rd dose anyway? Read here.

People who are seriously immunocompromised were already given the green light a few weeks ago to get a 3rd dose both in the U.S. and U.K. (Read here.)

Last week, the U.S. Food and Drug Administration (FDA) advisory panel voted AGAINST additional doses for ALL adults over age 16 (notably going against some previous statements from the Biden administration).

However, the committee voted IN FAVOR of 3rd doses for those aged 65+ who are 6 months past their 2nd dose. They also recommended expanding this eligibility to those < 65 who are at higher risk due to co-morbidities or occupational exposures, but these details are still to be fleshed out.

Notably this meeting only assessed 3rd doses for the Pfizer/BioNTech vaccine, which had already submitted its own data on waning immunity and the need for boosters.

Still unanswered:

❓What about those who received the Moderna vaccine?

❓ What about the 14+ million one-shot Johnson and Johnson vaccine recipients in the U.S?

Answers to these questions are *expected* to come soon.

While the FDA does not have to follow the recommendations of the advisory panel, they typically do, and we should know more about specific changes in U.S. policy later this week after an Advisory Committee on Immunization Practices (ACIP) meeting (September 22-23rd).

In the U.K., the Joint Committee on Vaccinations and Immunizations (JCVI) also recently announced plans to begin booster shots for adults aged 50+ who are 6 months past their 2nd dose as well as vulnerable younger populations. While many people received two shots of the Oxford/Astrazeneca vaccine as their primary series, JCVI is recommending that an mRNA vaccine be used as a booster for everyone (either Pfizer or ½ of a Moderna dose). This is based on data from the COV-BOOST trial showing a mix-and-match approach might be preferable for immune response.

➡️ Do we NEED boosters? Is immunity really waning?

That question is surprisingly difficult to answer, and scientists don’t all agree.

The recommendations are motivated by real-world data from Israel and the UK suggesting that protection against INFECTION with SARS-CoV-2 may decline with time, especially in the most vulnerable. This real-world data is quite messy and not straightforward to interpret (since the oldest and most vulnerable were vaccinated first), so not all scientists agree that the data are conclusive.

Importantly, vaccine protection against hospitalization and death seems to be holding up very well. Immunologists also point out that antibody responses are supposed to wane with time, leaving B and T cells to provide longer term immune memory.

Pfizer/BioNTech provided data showing a large increase in neutralizing antibodies after administration of a 3rd dose of vaccine. This is strongly suggestive that protection would be boosted at least in the short term, but how this translates into real world protection is not known (though some encouraging data are showing reduced infections after recent 3rd doses in Israel).

❓If the goal of boosters is to protect against serious disease, why boost now?

The arguments in favor of boosting are generally precautionary. Countries staring down the barrel of winter with already high case rates and hyper transmissible Delta want to use boosters to build their wall of protection higher and shield the most vulnerable from severe disease.

Many vaccines require more than a two dose primary series for lasting protection, so that could be the case for the COVID-19 vaccine as well (but because both the virus and the vaccine are brand new, we’re still feeling our way around these things).

While any boost in antibodies from the 3rd shot may be only temporary, during the current backdrop of high transmission it could nevertheless be well-timed to protect people from breakthrough infections AND tamp down transmission. This is because high neutralizing antibodies can increase the likelihood of snuffing out the infection out early before someone has a chance to transmit. When these levels come back down, it may take a few days for B cells and T cells to kick in once the virus starts replicating, allowing more time for mild illness and transmission– but still blocking progression to severe disease.

Another important debate about boosters is the ethics of 3rd doses for some while millions around the world are still waiting for 1st doses. The WHO has continued to plea for a “moratorium” on boosters and for countries with excess supply make doses available to countries in need. It seems clear that individual governments are not listening to these pleas and will prioritize the perceived needs of their populations for now. We know this leaves individuals who care about global vaccine equity in a tough spot, with some unsure whether they should accept a booster. While there is worthy debate on all sides, we tend to agree with the view that your decision to accept or forego a booster will not directly affect the supply in lower-and-middle-income countries, and in fact that dose would likely be wasted. Our governments and vaccine manufacturers need to be lobbied to provide global supply where needed but refusing your own booster will not transfer that dose elsewhere.

Besides lobbying, one opportunity for individuals is to make a donation to provide vaccines for COVAX (link below).


Boosters are happening, starting with older adults. Stay tuned for more details as they emerge–soon!

Those Nerdy Girls

Further links:

➡️ Donate vaccines to COVAX

“FDA advisory panel recommends booster doses of Covid-19 vaccine only for older and high-risk Americans”

“JCVI issues updated advice on COVID-19 booster vaccination”

Scientists’ recent letter about whether boosters are needed

“WHO chief urges halt to booster shots for rest of the year”

“Covax misses its 2021 delivery target – what’s gone wrong in the fight against vaccine nationalism?”

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