FDA advisers to vote on Moderna booster shots

Published: October 14, 2021 12:16 PM EDT
Updated: October 14, 2021 3:40 PM EDT
Moderna vaccine doses stored in a refrigerator. Credit: WINK News

An outside panel of the Food and Drug Administration’s vaccine experts is scheduled to vote Thursday afternoon on Moderna’s request to roll out booster shots of its COVID-19 vaccine for adults vaccinated at least six months ago. The vote will follow a meeting expected to last several hours discussing the safety and the need for an additional dose.

Though most studies currently suggest the vaccine remains highly effective at protecting most people against severe COVID-19 infections and death, Moderna and some federal health officials say a third, smaller dose could boost protection in the face of the highly contagious Delta variant and a looming flu season experts warn could be unusually severe for hospitals.

The FDA and CDC have already authorized Pfizer’s third shot for older and higher-risk Americans. More than 7.3 million vaccinated people have received a booster shot of Pfizer’s vaccine, according to the Centers for Disease Control and Prevention. Around 1.5 million have received a third dose of Moderna’s vaccine, which only some immunocompromised Americans are eligible to receive for now.

The FDA’s Vaccines and Related Biological Products Advisory Committee is also expected to vote Friday on Johnson & Johnson’s request to give a second dose to some “high risk” Americans as early as two months after they were first vaccinated with the single-shot vaccine.

“Our goal at the end of that is to hopefully have a harmonized approach to boosters for the three different vaccines, and hopefully try to harmonize — make it a little bit simpler for our recommendation for boosters in the general population,” Dr. Peter Marks, the FDA’s top vaccines official, said last week at an event hosted by the COVID-19 Vaccine Education and Equity Project.

This week’s meetings are just a key first step in the process of allowing booster doses for Moderna and Johnson & Johnson. State and local health officials are planning for the possibility that Moderna and Johnson & Johnson’s booster shots could be fully green-lit as early as next week.

After the advisory panel’s vote, the FDA is expected to move quickly to decide on a formal authorization for the booster shots. But before booster shots can be given, the CDC must also first issue guidance that would allow their use. The CDC’s Advisory Committee on Immunization Practices is planning to meet next week to vote on those recommendations.

The Biden administration has already moved to prepare vaccinators to begin administering Moderna’s booster shots, which the company says should come in a 50 microgram dose at least six months after adults were first vaccinated. From their current stock of vaccine, providers will be able to simply draw up half of the 100 microgram doses that made up Moderna’s first two shots.

While health officials have voiced concern over possible logistical challenges to having smaller dose sizes, Moderna said in documents submitted to the advisory panel that it chose to cut the size of its booster shots after seeing both it and the larger dose “induced at least a 66-fold rise” in antibodies. The company also claims the smaller dose would result “in a substantial increase” of vaccine supply for other countries, while potentially leading to milder side effects than from a larger third dose.

Like with Pfizer’s booster shots, Moderna says its trial data show that side effects from its proposed third dose would likely be similar to the second dose. The company’s study of the booster shot turned up no cases of myocarditis or pericarditis, the rare but potentially serious cases of heart inflammation that have been seen in a small number of people who received Pfizer and Moderna’s vaccines.

Moderna also said participants in its earlier trial have seen “significantly higher rates” of so-called breakthrough infections of COVID-19 as more time passes, suggesting that “lower antibody persistence and the increased transmissibility of the Delta variant could be contributing to higher breakthrough rates.”

In addition to presentations from Moderna and the FDA’s scientists, the committee is also scheduled to hear an update on Thursday from Israeli health officials who previously touted data suggesting the country’s nationwide Pfizer booster shot rollout curbed the Delta variant’s surge earlier this year.

Though the pace of new cases, hospitalizations, and deaths from COVID-19 have declined from their latest peak in the U.S., federal health officials have warned that transmission of the virus remains at dangerous levels as the country approaches “a potentially severe flu season this year” — raising concerns about a potential “twindemic.” More than 86% of counties nationwide remain at “high” transmission of COVID-19, according to the CDC’s tally.

Then on Friday, after voting on Johnson & Johnson’s booster shot request, the panel is expected to get a presentation from scientists on the findings of a clinical trial backed by the National Institutes of Health that tested mixing-and-matching COVID-19 booster shots from different manufacturers.

Data from the study, which was released Wednesday as a preprint that has yet to be peer-reviewed, suggest it could be safe and effective to administer what’s called a “heterologous” boost for most people. For example, recipients of Johnson & Johnson’s vaccine who received Pfizer’s booster shot saw antibodies reach levels correlated with high vaccine efficacy and turned up no safety concerns.

“These data suggest that if a vaccine is approved or authorized as a booster, an immune response will be generated regardless of the primary Covid-19 vaccination regimen,” the study’s authors wrote.