U.S. officials now say that people 50 and older can get a second COVID-19 booster shot to fortify their immune defenses against COVID-19. But for individuals in that group, the decision is complicated.
Here are considerations health experts say people should weigh.
WHAT IS THE RECOMMENDATION?
Last month, the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention said any person aged 50 and older can get a second COVID-19 booster of an mRNA vaccine from Moderna and Pfizer/BioNTech at least four months following their last shot.
The same goes for people who are severely immunocompromised aged 12 and up as well as those who have received two doses of Johnson & Johnson's shot.
Dr. Peter Marks, director of FDA's Center for Biologics Evaluation and Research, said the aim is to give older adults the option to top up waning vaccine protection against severe disease as the virus continues to circulate.
The highly transmissible omicron BA.2 subvariant has fueled cases in other countries and is now sweeping the United States, accounting for the majority of all coronavirus infections here.
WHAT IS THE EVIDENCE?
Data presented to a panel of FDA advisers last week showed that current vaccines lose much of their effectiveness in staving off infections from the omicron variant but still do a good job at preventing severe disease, especially in people with healthy immune systems.
Concerns about the variant's ability to evade the vaccine as well as data showing the shots become less protective over time prompted U.S. health officials to authorize a second booster.
Evidence in favor of a second booster comes from an Israeli study of more than 1.2 million adults published last week in the New England Journal of Medicine. It showed that a fourth dose of the Pfizer/BioNTech vaccine lowered rates of severe COVID-19 among those age 60 and older but offered only short-lived additional protection against infection.
WEIGHING THE RISK
The decision to get a fourth dose should take into account a person's individual risk factors, experts say.
For people 65 and older, the immune compromised, or those 50 and older with serious medical conditions, the answer is "pretty easy," said Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center. They should get a second booster.
But for healthy people over 50, experts are unsure available data makes a clear case for them to get another booster.
"There's no clear evidence that vaccine protection against severe illness is waning in healthy adults with functioning immune systems," said Dr. Michael Daignault, and emergency physician and chief medical advisor to Reliant Health Services, an Atlanta-based testing company.
Daignault said the Israeli study may have been flawed by confounding factors such as other preexisting health conditions and behavior.
"I'm not convinced that most people need a fourth dose - or second booster - at this time," he said.
Dr. Gregory Poland, a former FDA vaccine advisory panel member and head of Mayo Clinic's Vaccine Research Group, said the decision is challenging for many.
"I get many, many calls from my physician colleagues at the clinic and around the United States, wondering what to do," he said.
For people who have had a third shot, the risk of severe disease is already pretty low, said Dr. Jesse Goodman, an infectious disease expert at Georgetown University and a former FDA chief scientist.
Goodman said a fourth dose "may reduce it further, but we don't know for how long. That's why this is such a difficult call," he said.
Goodman, who is 70, and Poland, who is 66, both said they are holding off on a fourth dose based on their current health.
Because protection from a second booster is likely short-lived, Poland suggested people may want to time their shot for a trip, a high-risk event, or a new surge in cases.
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