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This week, the US Food and Drug Administration is expected to authorize the first updated versions of COVID-19 boosters since the pandemic began.
The new vaccines are reformulated versions of the Moderna and Pfizer-BioNTech vaccines. These are known as “bivalent” vaccines because they are designed to protect against the original strain and the highly contagious omicron variant.
Specifically, the vaccines are programmed to target the omicron subvariants BA.4 and BA.5, which are the dominant strains infecting humans and the most adept at sneaking around the immune system.
The hope is that the vaccines will boost people’s weakening immunity and provide stronger protection against contracting the virus, spreading it, and getting sick with COVID and prolonged COVID.
The Biden administration plans to begin offering the new vaccines after Labor Day to help reduce the impact of what could be another spike in infections this fall and winter.
“This is a really important moment in this pandemic,” Dr. Ashish Jha, the White House’s COVID-19 response coordinator, told NPR. “This is the first major vaccine improvement — the first major vaccine change — in two and a half years.”
But the formulation of boosters and the process for authorizing them has sparked debate among scientists.
For the first time, the FDA is evaluating how well vaccines work without the results of tests done directly on people. To save time, the FDA initially evaluates vaccines with tests on mice alongside the results of human tests of an earlier version of the bivalent vaccine.
Some experts worry that mouse studies are not very reliable in predicting how well vaccines work in humans.
“It can be problematic if the public thinks that the new bivalent boosters are a super strong shield against infection and therefore increase their behavioral risk and expose themselves to more viruses,” says John Moore, an immunologist at Weill Cornell Medicine.
But federal officials are defending the decision.
Studies in mice show that the new vaccines may be about 20 times more protective against omicron than the original vaccines and about five times more protective than the first attempt to create bivalent omicron-specific vaccines, Dr. Peter Marks, director of The Center for Biologics Research Evaluation and Research at the FDA, told NPR in an interview.
“This makes us feel confident that they will do what they are intended to do, which is to produce a good immune response against the BA.4/5 variant, as well as renew our overall response, given the original component of the vaccine,” Marks says.
The decision to rely on mouse studies became necessary after the FDA in June rejected new boosters targeting the original strain of omicron, known as BA.1, and instead asked vaccine companies to develop new injections targeting the strains. who have replaced him.
Some scientists think there’s a chance the new vaccines could also give people immunity that lasts longer than the original vaccines, and maybe even protect against new variants emerging. But more research is needed to confirm this.
Some experts say the data from BA.1 boosters show that any potential improvement could be quite modest at best.
“We want a silver bullet. And the booster turned into the silver bullet. And we’re putting all our eggs in the vaccine basket,” says Dr. Celine Gunder, a senior fellow at the Kaiser Family Foundation. “I’m very skeptical about how much improvement these vaccines will bring in terms of population immunity and prevention of severe disease.”
Gounder also worries that the country has given up on doing anything else to protect people, such as wearing masks and improving ventilation.
But others are more optimistic about the new boosters.
“I’m personally very excited about bivalent vaccines,” says Jenna Gutmiller, assistant professor of immunology at the University of Colorado.
“We really need an updated vaccine to provide protection against current omicron viruses, as well as potentially all future omicron variants,” says Guttmiller. “I think it will be fine.”
After the FDA clears the vaccines, advisers from the Centers for Disease Control and Prevention will meet Thursday and Friday to decide whether to recommend them and who should get them. Then CDC Director Rochelle Walensky would have to sign off on that recommendation.
Some experts say that only people who are at high risk because of their age or their backgroundg health problems should get another boost as the first shots still protect most people from serious illness. Others say that anyone age 12 and older who has not been recently infected or boosted should get another shot.
“I would say that anyone who’s been more than six months since their previous boost or previous infection should go get a boost,” says E. John Wherry, an immunologist at the University of Pennsylvania.
“Any opportunity to get more boosters into the population to increase vaccine uptake is going to be a positive thing to help us get through this pandemic,” Wherry says.
The Biden administration has purchased more than 170 million doses of the new boosters, which are set to become available after Labor Day.
It remains unclear how much demand there will be for the new boosters, given that many eligible people have yet to receive their first or second boosters.