The Food and Drug Administration on Wednesday authorized booster doses for the Johnson & Johnson COVID-19 vaccine and for certain populations who got the Moderna COVID-19 vaccine, and cleared the way to "mix and match" boosters for all three coronavirus vaccines.
Everyone who received the Johnson & Johnson COVID-19 vaccine can receive a booster as soon as two months after the first dose, effectively transforming the country’s only single-shot vaccine into a two-dose regimen.
By Friday, millions of qualifying people vaccinated with Moderna could get a supplemental dose six months after the second dose. Those 65 years old or older, with certain co-morbid conditions or in high-risk jobs or institutions like homeless shelters and prisons all qualify for another dose.
About 60 percent of adults younger than 65 are eligible for a booster because of an essential job or comorbidity, according to the Centers for Disease Control and Prevention. The booster dose is half of the original 100-microgram dose.
In addition, Americans don’t have to be picky about which shot they receive. The FDA said it amended the emergency use authorizations of all three vaccines to allow “mixing and matching,” whether one's vaccine card reads Pfizer-BioNTech, Moderna or Johnson & Johnson.
The action tees up a meeting of advisers to the CDC on Thursday. The recommendations of the CDC’s Advisory Committee on Immunization Practices cannot alter the FDA’s emergency use authorization, but influence how public health resources are directed. The advisers and CDC could still narrow the populations recommended for a boost.
The FDA emergency use authorizations come less than a week after the agency's independent advisory committee unanimously recommended that special populations receive a third shot of the Moderna vaccine, and everyone who received one Johnson & Johnson shot receive a second.
Boosting Johnson & Johnson recipients with an mRNA vaccine such as those by Pfizer-BioNTech or Moderna may be seven to 12 times as powerful, according to a phase 1-2 trial of 458 volunteers backed by the National Institutes of Health. And Johnson & Johnson recipients saw a much higher boost than patients originally vaccinated with two mRNA shots.
But the study tested a Moderna shot at a full 100-microgram dose, not the 50 microgram dose authorized by FDA.
Moderna and Pfizer-BioNTech patients also saw a slightly better boost with heterologous vaccines.
The “mix-and-match” approach is not all that unusual, according to some FDA advisers.
“It’s quite typical in vaccine programs to provide interchangeability data in studies to allow for the flexibility that would lead to a successful vaccination program,” said Paula Annunziato, vice president of vaccine clinical development at Merck, last week.
Boosters are likely to better protect people with weaker immune systems and people frequently exposed to COVID-19. In others with strong immune systems but at high risk of infection, boosters could also stave off asymptomatic cases and mild cases, at least temporarily, reducing the risk of transmission for people who may have unvaccinated loved ones.
Federal health officials also hope a booster could reduce rates of long-haul COVID, but the data on breakthrough cases and long COVID is still evolving.
The FDA's move will deepen the rift between the Biden White House and the World Health Organization, which wants a moratorium on booster shots in wealthy countries, citing dismal vaccination rates in low-income countries.
A debate over to what degree vaccine acquired immunity may be waning in the U.S. also divides independent scientists close to the White House.
Some of the president’s outside scientific advisers argue the White House and FDA moved ahead of the data on declining immunity, saying that memory immune cells are likely to confer long-term protection even as antibodies wane.
A White House plan to roll out boosters for every American was scaled back after FDA’s advisers rejected the plan as premature.
Paul Offit, one of the FDA’s advisers on COVID-19 vaccines and director of the Vaccine Education Center at Children’s Hospital of Philadelphia, said there has been a “real pressure to boost.”
“Often we on the committee get the data a day before,” he said. “Obviously we want to get past this pandemic, but it seems to everybody like the way to get past the pandemic is to get the unvaccinated vaccinated.”
“The people at the adult hospital next door, the people in the ICU, it’s not because they haven’t gotten a third dose. It’s because they haven’t gotten any doses,” he said.
More than 15 million people have received the Johnson & Johnson vaccine. Both the FDA and the CDC consider the vaccine highly effective against severe cases, but less effective than the Pfizer-BioNTech and Moderna vaccines.
The company argued two doses of its vaccine would amp up efficacy in preventing any illness to 94 percent, comparable to the other authorized vaccines.
“I think that were this not a pandemic, this always would have been a two-dose vaccine,” said Offit.
Moderna also tested whether immunity had waned during the delta variant by comparing people who received the vaccine earlier in the clinical trial with people who initially unknowingly received a placebo and “crossed over” to receive a real vaccine about five months later, in response to a request by FDA to study it.
People who got the second shot more recently had twice the odds of fending off a rare severe breakthrough case caused by delta. But FDA was not given the opportunity to independently verify the results.
Boosters for middle-aged people?
FDA is also expected to eventually authorize shots for people as young as 40 years old in the coming months, according to some media reports.
Booster proponent Peter Marks, who directs the FDA’s Center for Biologics Evaluation and Research, floated the 40-year-old threshold at the end of a meeting of FDA advisers last week, citing Israeli data on waning immunity from the Pfizer vaccine.
“They did present data that seems [to just me] compelling in the 40-and-up age group,” Marks said.
Marks has also helmed the FDA’s Office of Vaccines Research and Review in place of its top two regulators, who reportedly are retiring in protest of the fast booster rollout pace.
For people younger than 40, the rate of severe cases after boosters was not high enough to make statistically significant conclusions.
At last week's meeting, Marks suggested taking a vote on lowering the eligibility age.
But the idea was shot down by committee chair Arnold Monto, an epidemiologist at the University of Michigan's School of Public Health, who expressed pessimism that it would pass unanimously.
“We don’t want to do that,” said Monto. “People will start counting the votes ‘no.’”
Offit expressed concern that the Israeli data may be an outlier.
“The Israeli data keeps getting presented to us but in many ways it’s at variance with data generated from the United States, where we don’t see a falloff in efficacy from severe illness,” said Offit.
Former FDA drug reviewers say agency advisers were hesitant to expand eligibility beyond the especially vulnerable.
“It may be that we have the broader population needing another dose,” said Jesse Goodman, a Georgetown University biotech expert and former FDA chief scientist. “But right now we have limited safety data. And you’re being quite proactive to do this with the at-risk populations that the committee already proposed.”