Yesterday, the Food and Drug Administration authorized a second booster shot of the Pfizer-BioNTech and Moderna coronavirus vaccines for people 50 and older, a decision intended to help shore up protection against severe illness. The shots, which can be given at least four months after a first booster dose, are not a solution to the pandemic. But with a still-more-transmissible version of the omicron coronavirus variant becoming dominant in the United States, even a short-term immunity boost among those at risk of severe illness could provide a valuable layer of protection. Tuesday’s announcement from the FDA also included an update for people who are immunocompromised. They are now eligible for an additional booster, too. They initially received a series of three vaccinations and have already been eligible for one booster. Now, they, too, may get a second booster, meaning they can receive a total of five shots.
The Food and Drug Administration (FDA) has also announced plans to convene its Vaccines and Related Biological Products Advisory Committee on April 6 to consider future COVID-19 vaccine booster doses and the process for selecting specific strains of the SARS-CoV-2 virus for COVID-19 vaccines to address current and emerging variants. So now that an additional booster is approved, that begs the question who should get a fourth COVID shot? As coronavirus case counts continue to plummet across the United States, people’s immunity may be declining, too. Several studies have found that while mRNA booster shots have been successful at preventing hospitalization and death, their effectiveness against infections is waning. One reason older adults may benefit from an additional booster shot is because as the immune system ages, it tends to weaken and does not produce the same quantity or quality of antibodies as it did when it was younger. On top of that, older adults often have other medical conditions that take up the body’s attention, putting them at higher risk of severe disease such as diabetes, hypertension, obesity and chronic kidney disease which are all risk factors for severe COVID. In one study, published on a preprint server in February, scientists reviewed the health records of about 1.1 million people over 60 who had received a fourth dose and compared them with those who had received just three doses. They found that the rate of confirmed infections, as well as that of severe illness, was lower in people who had gotten their fourth shot. The second study, published Wednesday in The New England Journal of Medicine, looked at Israeli health care workers of all ages and found that both Pfizer’s and Moderna’s fourth shots bolstered antibody levels, though they were not very good at preventing infection.
If another surge is just around the corner, for instance, seniors may benefit from getting an extra shot now. But if the next wave doesn’t occur until the summer or even the fall, getting a booster now could backfire because the recipients’ immunity might start to wane by the time they need protection the most. Current vaccines are based on the original strain of the coronavirus, so getting a booster now may also do little to protect against future variants. Pfizer and Moderna are testing new Omicron-specific versions of the Covid booster. And other researchers are investigating vaccines that boost mucosal immunity in the nose, as well as protein-based shots that may be better at protecting against the coronavirus in the future.