With the rise of the Delta variant, there is renewed interest in COVID vaccine efficacy and whether boosters are needed.
First, let’s clarify what is meant by “booster”. A booster could be another shot of the existing vaccines – for example, if you got 2 shots of Pfizer vaccine, a booster might be a 3rd shot. So far however, most data show there are still high levels of neutralizing antibodies at 6 months after completion of the vaccine series for all three vaccines available in the US (Johnson & Johnson, Pfizer, and Moderna).
However, special populations who had a less robust immune response (e.g. those on immunosuppressive medications, cancer patients, etc.) produce less antibodies and immunity. They might benefit from an extra dose.
There is also an ethical issue of giving booster doses to people who are fully vaccinated in the United States before others worldwide even get a first dose. The World Health Organization recently called on wealthy nations to stop the distribution of Covid-19 booster shots, citing vaccine inequity around the world. The agency said the halt should last at least two months, to give the world a chance to meet the Director-General’s goal of vaccinating 10% of the population of every country by the end of September.
Another type of “booster” is a vaccine that is tweaked to include coverage specifically against the newer strains (e.g. Alpha, Beta, Delta, etc.). Both Pfizer and Moderna are working on these boosters. But they are at least 6 months away from being ready for public consumption. It takes time to develop, test, get approval and mass produce the new vaccines.
There are ongoing studies looking at mixing vaccines. For example, if you completed the 2nd dose Pfizer series, can you get a booster of the Moderna vaccine? Is it safe? Does it confer any additional immunity? Those trials started in June so we won’t know until at least October 2021.
TAKE HOME MESSAGE: Currently not enough data to support booster doses, except possibly in special populations. And we should not give boosters until at least 10% of the population population of every country is vaccinated.