Close-up image of vaccination being given in upper arm of older individual

Older adults and people who are immunocompromised may now receive a second booster shot to better protect themselves against current coronavirus variants, the Food and Drug Administration announced early Tuesday.

Under the new guidance, those aged 50 years and older are recommended to receive a jab from either the Pfizer-BioNTech or Moderna mRNA vaccines at least four months after receipt of their first booster. Immunocompromised people aged 12 years and older may receive a second Pfizer booster, and those 18 years and older are also eligible for the additional Moderna shot, the agency said.

Data shows that a first booster’s efficacy wanes within a few months, and COVID-19 has had a disproportionately adverse effect on older people and those with comorbidities. The latest evidence is in favor of receiving a fourth dose now, according to Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research. This will allow added protection while decisions are made about vaccines for the fall season, he said in a Tuesday news call.

The FDA’s decision to authorize a second booster was largely based on data from a study of more than 700,000 older patients in Israel, Marks added. That study found that an additional dose provided the most protection at about four months after receipt of an initial booster.

Ready for a surge 

At-risk individuals will now have an opportunity to protect themselves before a possible new surge in infections hits the United States, Marks said.

“[We are] hoping that by taking this action we will help allow people to take steps to protect themselves should we have another wave come through this country,” he said.

Officials are currently planning the future of vaccines in light of ever-changing variants, he also noted. The FDA’s vaccine advisory committee is set to meet next week to discuss issues such as whether another booster or vaccination will be needed in the fall, and whether a variant-specific shot or a vaccine with protection against multiple variants is warranted, Marks said. 

4th dose in healthcare staff

In the meantime, evidence from another study in Israel has found that a fourth dose of the Pfizer or Moderna COVID-19 vaccines has only moderate efficacy in relatively younger healthcare workers.

A fourth dose is “immunogenic, safe and somewhat efficacious” against symptomatic disease in this population, investigators reported. But the study also found that an added dose provided low efficacy against infections. What’s more, high viral loads were prevalent among the more than 1,000 participants. This suggests that the infected workers were also infectious, the researchers noted.