Moderna COVID-19 boosters: FDA panel endorses lower-dose shots for seniors, high risk

A panel of independent advisers to the U.S. Food and Drug Administration unanimously voted to endorse lower-dose booster shots of Moderna’s COVID-19 vaccine for seniors and other high-risk groups.

The panel recommended a booster shot for seniors, as well as younger adults with other health problems, jobs or living situations that put them at increased risk from COVID-19.

The recommendation is non-binding but it’s a key step toward expanding the U.S. booster campaign to millions of more Americans. Many people who got their initial Pfizer shots at least six months ago are already getting a booster after the FDA authorized their use last month — and those are the same high-risk groups that FDA's advisers said should get a Moderna booster.

But there's no evidence that it's time to open booster doses of either the Moderna or Pfizer vaccine to everybody, the panel stressed — despite initial Biden administration plans to eventually do that.

The coronavirus still is mostly a threat to unvaccinated people — while the vaccinated have strong protection against severe illness or death from COVID-19.

"I don’t really see a need for a ‘let it rip’ campaign for everyone," said Dr. Michael Kurilla of the National Institutes of Health.

As for the dose, the initial Moderna vaccination consists of two 100-microgram shots. But Moderna says a single 50-microgram shot should be enough for a booster.

The FDA convened its experts this week to weigh in on who should get boosters and when for those who received the Moderna and J&J shots earlier this year. On Friday, the panel will hear evidence for the J&J booster shot and will also look into the safety and effectiveness of mixing and matching different brands of vaccines — something regulators have not endorsed so far.

U.S. officials continue to stress that the priority is to get shots to the 66 million unvaccinated Americans who are eligible for immunization — those most at risk as the extra-contagious delta variant of the coronavirus has spread across the country.

"It’s important to remember that the vaccines still provide strong protection against serious outcomes" such as hospitalization and death from COVID-19, FDA vaccine chief Dr. Peter Marks said Thursday.

But Marks said it’s also become clear there is some waning of protection against milder infections with all three of the COVID-19 vaccines used in the U.S. And he encouraged the advisory panel to consider if the evidence backs similar booster recommendations for all of them as well since that would "create the least confusion" for the public.

After the FDA advisers give their recommendation on boosters, the agency itself will make a decision on whether to authorize boosters. Then next week, a panel convened by the U.S. Centers for Disease Control and Prevention will offer more specifics on who should get them. Its decision is subject to approval by the CDC director.

An estimated 103.5 million Americans are fully vaccinated with Pfizer’s vaccine, CDC data shows. Another 69 million are fully vaccinated with the Moderna shot, and nearly 15 million people received the J&J vaccine. 

The FDA panel meetings come as U.S. vaccinations have climbed back above 1 million per day on average, an increase of more than 50% over the past two weeks. The rise has been driven mainly by Pfizer boosters and employer vaccine mandates. An estimated 8.9 million Americans have received a Pfizer booster dose since Aug. 13, according to the CDC.

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Evidence that Moderna’s vaccine protection is waning was presented during the meeting. Moderna's Dr. Jacqueline Miller told the FDA's advisers that as the delta variant surged in July and August, people who were more recently vaccinated had a 36% lower rate of "breakthrough" infections compared with those vaccinated longer ago.

As for the dosage, the initial Moderna vaccination consists of two 100-microgram shots. But Moderna says a single 50-microgram shot should be enough for a booster. The company said that would trigger fewer uncomfortable shot reactions such as fever and achiness while also leaving more vaccine available for the global supply.

A study of 344 people found the booster shot six months after initial vaccinations restored virus-fighting antibodies to levels seen after recipients' last dose — and that included large jumps in antibodies able to target the delta variant, Miller told the panel.

One very rare side effect of both the Moderna and Pfizer vaccines is heart inflammation, particularly among young men soon after the second dose — and one lingering question is whether another dose could spark more cases. Moderna's booster study wasn't large enough to spot such a rare risk.

However, Israel began offering Pfizer boosters sooner than the U.S. and to more of its population. Dr. Sharon Alroy-Preis of Israel's health ministry told the FDA panel on Thursday that after 3.7 million booster doses administered, there's no sign the extra shot is any riskier — despite an intense investigation into heart inflammation.

A Pharmacy Administers Third Doses Of Covid-19 Vaccines

A pharmacist administers a booster dose of the COVID-19 vaccine to a customer at a pharmacy in Livonia, Michigan, on Aug. 17, 2021. Photographer: Emily Elconin/Bloomberg via Getty Images

In the U.S., scientists are divided about exactly who needs boosters and their purpose — whether they're needed mostly for people at risk of severe disease or whether they should be used to try to reduce milder infections, too. While Pfizer's boosters are only for certain high-risk groups of Americans, Israeli officials credit wider booster use in their country to stemming the delta surge.

"There is no question in my mind that the break of the curve was due to the booster dose," Alroy-Preis said in response to FDA advisers who noted that other countries have seen a lowering of delta cases without widespread booster use.

As Thursday’s deliberations began, FDA’s advisers also highlighted one confusing issue: People with severely weakened immune systems already can get a third full dose of the Moderna vaccine soon after the initial vaccinations — so a question is whether they should be eligible for a booster, too, which would be their fourth dose.

RELATED: COVID vaccines: The difference between a 3rd shot and a booster

On Friday, they’ll turn to the topic of the single-dose J&J vaccine — and documents the FDA released suggest this week’s decisions will be equally difficult.

In an online review made public this week, FDA scientists indicated they were wrestling with whether recipients of the J&J vaccine even need another dose, and if so when they should get it: six months or as early as two months. The experts didn’t reach a firm conclusion, citing shortcomings with J&J’s data, including little information on protection against the extra-contagious delta variant.

FDA reviewers wrote that a study of the two-month booster plan suggests "there may be a benefit," while pointing to only small numbers of people who got another shot at six months instead.

Overall, the J&J vaccine "still affords protection against severe COVID-19 disease and death," the FDA’s reviewers concluded. But data about its effectiveness "are consistently less" than the protection seen with Pfizer and Moderna shots.

For its part, J&J filed data with the FDA from a real-world study showing its vaccine remains about 80% effective against hospitalizations in the U.S.

RELATED: COVID-19 vaccines: Study finds J&J recipients better off with Moderna, Pfizer booster

The Associated Press contributed to this report. It was reported from Cincinnati and Los Angeles.