WASHINGTON — Americans age 50 and older can receive a second COVID-19 booster if it’s been at least four months since their last vaccination, a chance for extra protection for those most at risk should the coronavirus bounce back.
The Food and Drug Administration on Tuesday approved an extra dose of the Pfizer or Moderna vaccine for this age group and for certain younger people with severely compromised immune systems.
Hours later, the Centers for Disease Control and Prevention recommended the additional shot as an option, but paused to urge those eligible to rush in and get it immediately. This decision extends the additional booster to millions more Americans.
“Anyone who is eligible for an initial booster who has not yet received one must do so,” said FDA vaccine chief Dr. Peter Marks. But the second refresher is only for these higher-risk groups, as evidence may be declining and the FDA has ruled the option will help save lives and prevent serious consequences.”
The move comes at a time of great uncertainty. COVID-19 cases have dropped to low levels after the winter surge in the super-contagious Omicron variant. CDC data shows that two vaccine doses plus a booster shot still provide strong protection against serious illness and death.
“And the reason for that is because we know that we’ve talked about it in the past, after four or five months, effectiveness tends to decline,” said Jen Ashton, ABC News correspondent.
But an Omicron subvariant is causing a worrying rise in infections in Europe — and spreading in the US — even as vaccination has stalled. About two-thirds of Americans are fully vaccinated, and half of those eligible for an initial booster shot have not yet received one.
“It’s starting to spike in many parts of the country, so it makes sense that many people would want to boost their immunity when we’re potentially headed for a spike,” said Doctor John Brownstein of Boston Children’s Hospital.
Pfizer had asked the FDA to clear a fourth injection for people ages 65 and older, while Moderna requested another dose for all adults “to provide flexibility” so the government can decide who really needs one.
The FDA’s Marks said regulators set the age at 50 because that’s when chronic conditions like heart disease and diabetes become more common and the risks of COVID-19 increase.
Previously, the FDA had approved a fourth dose of vaccine only for immunocompromised individuals 12 years and older. Tuesday’s decision also allows them one more booster shot — a fifth dose. Marks said these patients are more likely to lose their immune protection earlier and may therefore benefit more from additional protection. Only the Pfizer vaccine can be used in children 12 years and older; Moderna’s is for adults.
There is limited evidence of how much benefit another booster could offer at the moment. The FDA made the decision without input from its independent panel of experts, who have wrestled with how much data is needed to expand shots.
“There might be reason to fill up the tanks a little bit” for older people and people with other health conditions,” said University of Pennsylvania immunologist E. John Wherry, who was not involved in the government’s decision.
But while he encourages older friends and relatives to take the advice, Wherry, 50 – who is healthy, vaccinated and boosted – has no plans to get a fourth shot straight away. With protection against serious illness still going strong, “I’ll wait until it looks like there’s a need.”
None of the COVID-19 vaccines are as potent against the omicron mutant as previous versions of the virus. Protection against minor infections also naturally decreases over time. But the immune system puts up multiple layers of defense, and the kind that prevents serious disease and death endures.
During the US Omicron wave, two doses were nearly 80% effective against needing a ventilator or death — and a booster shot increased that protection to 94%, the CDC recently reported. Vaccine effectiveness was lowest – 74% – in immunocompromised people, the vast majority of whom had not received a third dose.
US health officials also looked to Israel, which introduced a fourth dose for people age 60 and older at least four months after their last vaccination during the Omicron surge. The FDA said a review of 700,000 administered fourth doses revealed no new safety concerns.
Preliminary data posted online last week suggested some benefit: Israeli researchers counted 92 deaths among more than 328,000 people who received the additional vaccine, compared with 232 deaths among 234,000 people who missed the fourth dose.
What is far from clear is how long an additional benefit from another booster would last and when to get it.
“The ‘when’ is a really difficult part. Ideally we would time the booster doses just before the spikes, but we don’t always know when that will be,” said Dr. William Moss, a vaccines expert at the Johns Hopkins Bloomberg School of Public Health.
Also, a longer interval between shots helps the immune system build stronger, more cross-reactive defenses.
“If you get a booster too close together, there’s no harm – you just won’t benefit much,” Wherry said.
The latest booster addition may not be the last: next week the government will hold a public meeting to discuss whether everyone might need a fourth dose of the original vaccine or an updated shot in the fall.
Even if higher-risk Americans are boosted now, Marks said they may need another dose in the fall if regulators decide to tweak the vaccine.
To this end, studies are currently underway in humans – with targeted Omicron injections alone or in combination with the original vaccine. The National Institutes of Health recently tested monkeys and found “no significant benefit” from using a booster that targets only Omicron.
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