The recommendation mirrors the eligibility criteria for the Pfizer-BioNTech booster, which was authorized in September. Nearly 70 million Americans have been fully vaccinated with the Moderna vaccine, and millions of them would be eligible for a follow-up dose six months after vaccination if the agency authorizes the extra shot, which would be half the dose initially given.
The recommendation will now be considered by FDA officials, who are expected to reach a decision on the Moderna booster within days. An advisory committee to the Centers for Disease Control and Prevention that makes recommendations on how vaccines should be used is scheduled to meet Wednesday.
Boosters are a key part of the Biden administration's plan to manage the pandemic, and the outside advisers agreed they are an important tool for select groups of people. Cases of covid-19 have been declining in the United States as the lethal fourth-wave of the pandemic, fueled by the delta variant, appears to be ebbing. But public health experts remain worried about the possibility of another surge this winter as colder weather drives people indoors, where transmission chiefly occurs.
Some health experts have argued that there is not enough evidence to justify administering boosters to certain populations, especially younger, healthier people who, if they become infected, are likely to have asymptomatic or mild infections. But several Biden health officials believe it is important to reduce cases in vaccinated people, even if they do not result in hospitalization, to bring down the overall caseload.
At the start of Thursday's advisory committee meeting, Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, outlined the potential rationale for boosters. He said all three of the vaccines available in the United States remain highly protective against severe outcomes, but added that even milder cases may warrant prevention.
"Vaccine effectiveness against mild and moderate disease does appear to wane over time for the different vaccines, and we do need to account for the fact that mild to moderate covid-19 can be associated with adverse outcomes, such as blood clots and long covid-19, even in those who have breakthrough infections after vaccination," Marks said.
Several of the advisers pushed back on the notion that extra shots are needed for all Americans and said they worried the emphasis on boosters could distract from the potential of standard vaccine regimens to end the pandemic, which has killed more than 720,000 people in the United States.
"The effect of a booster is much less than vaccinating unvaccinated individuals - that means both here and abroad," said Eric Rubin, editor of the New England Journal of Medicine and a member of the advisory committee. "If we want to get out of this thing, we've got to vaccinate the unvaccinated."
The vote to recommend boosters for older adults and people at risk because of underlying health conditions or exposures at their jobs came after a full-day examination of data on the safety and effectiveness of a booster. Several experts noted there was only minimal safety data. Moderna presented studies of about 350 people who were given a booster dose, six months after their initial shots.
While the committee gave a thumbs up to boosters for some people, a separate discussion about whether people as young as 18 should be eligible for an extra dose triggered spirited objections from several members.
"I'm not convinced that the epidemiology of the pandemic at the moment in the U.S. supports this request," said Archana Chatterjee, dean of the Chicago Medical School.
"I worry that we haven't clearly defined what the goal of this vaccine is. If the goal of this vaccine is to prevent asymptomatic or mild infection, that is a goal that we have set for no other vaccine. . . . That is a high bar to which we hold no other vaccine," said Paul Offit, a vaccine expert at Children's Hospital of Philadelphia.
Some outside experts criticized the discussion as shortsighted and warned that cases could climb again, as they have several times throughout the pandemic.
"You can't just say it's getting better. The surge is coming down just like the surge came down last winter and last summer. That's a shortsighted discussion," said Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. "I'm incredibly doubtful this is our last surge, and I think some geographic areas are going to get hit again."
The committee's acting chairman, Arnold Monto, said he hoped a framework could be developed to determine if a booster is warranted in younger age groups going forward - and to better understand the potential benefits and risk.
"The concern that I have is that we don't want to wait until we see some more severe infections in the under 65-year-old general population, because getting this vaccine out takes time and requires extreme logistic efforts," said Monto, a professor of public health and epidemiology at the University of Michigan.
Committee members reviewed data that showed Moderna's two-shot regimen remains robustly protective at more than five months after vaccination: 93% effective in preventing all virus-related symptomatic illness and 98% protective against severe cases.
To make the case for boosters, Jacqueline Miller, head of Moderna's infectious-disease therapeutic area, presented data showing that six to eight months after vaccination, antibody levels dropped in vaccine recipients. A half-dose booster at least six months after initial vaccination restored those antibodies in a study of nearly 300 people.
Miller also presented data on breakthrough cases among people in the clinical trial of the company's vaccine, which began in summer 2020. Among those vaccine recipients, there was a clear uptick in breakthrough infections this July and August.
"Prior to July, the maximum number of cases reported in [vaccinated individuals] in a single month was 23," Miller said. "This increased to 81 cases in July and 169 cases in August, with 97 percent of these cases due to the delta variant."
A Moderna analysis showed that protection against infections appears to diminish over time. People vaccinated earlier in the large clinical trial were more likely to have breakthrough cases this July and August compared with the group that received the placebo in the trial and thus were vaccinated more recently.
During the meeting, questions were raised about why Moderna has not made a bigger commitment to supply doses to low- and middle-income countries. The Biden administration is frustrated that Moderna has not made a greater commitment to supplying doses to the rest of the world.
Miller referred to an open letter from Moderna chief executive Stephane Bancel. She said the company was not enforcing its patents during the pandemic and added that a half-dose instead of a full-dose booster will "make more vaccine available for the world, so that frees up a billion extra doses."
Representatives from Israel presented data on that country's experience with Pfizer-BioNTech booster doses, showing that as the country faced an uptick in infections this summer, the implementation of a booster campaign - initially targeted at adults 60 and older - helped thwart the rise in infections and severe cases in vaccinated people.
They also presented data showing that across age groups, including younger people, the rate of infection dropped after a booster dose. The rate of severe disease also dropped for people 40 and older. There were not enough severe cases among younger people to estimate a benefit.
Fully vaccinated people "were part of the wave, some of them getting severely ill and dying," said Sharon Alroy-Preis, director of public health services for Israel's Ministry of Health. "There is no question in my mind that the break of the curve was due to the booster dose."
On Friday, the same committee will meet at an all-day meeting to make a recommendation about a possible booster dose of the Johnson & Johnson vaccine.
It will also review data from a National Institutes of Health trial that tested whether mixing and matching booster doses from different companies was feasible. If the committee deems it safe for a person to receive a different booster than their primary vaccination, it could simplify logistics.
Published : October 15, 2021
By : The Washington Post