Should COVID vaccines be given annually? Proposal divided US scientists
Scientists are divided over the FDA’s proposal to update COVID-19 vaccines once a year, similar to the agency’s approach to updating flu vaccines. At a meeting of the Food and Drug Administration’s Vaccine Advisory Committee on Jan. 26, some researchers argued that the plan would help streamline the country’s complex COVID-19 immunization schedule and may boost uptake as a result.
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But others weren’t convinced that the vaccine should be updated every fall in the United States — or whether healthy adults should be urged to receive an annual COVID-19 shot at all. The proposal, released Monday, is “not a bad idea in theory,” says Angela Shin, a vaccinologist at Children’s Hospital of Philadelphia in Pennsylvania. But she wonders if the data supports updating the vaccine formulation once a year, because SARS-CoV-2 generates new variants at a different rate than influenza. says Shin, a former member of the US Centers for Disease Control and Prevention (CDC) Advisory Panel on Immunization Practices.
The update schedule for influenza vaccines is based on the well-documented seasonal pattern of emergence of new strains: selection of Northern Hemisphere vaccine strains depends in part on releases that circulated widely during the previous Southern Hemisphere winter. Although there is some evidence that SARS-CoV-2 also spreads seasonally, this pattern is not as predictable as the flu.
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“We understand the seasonality of influenza, and we know exactly when to get vaccinated for optimal effect,” says Luciana Borio, former acting chief scientist at the Food and Drug Administration and now a global health specialist at the Council on Foreign Relations in New York City. But “we simply don’t know whether people need to be vaccinated every year or less frequently to protect against severe COVID.”
In addition, SARS-CoV-2 variants do not sweep the world uniformly as influenza strains do, which means that it will be difficult to coordinate the composition of the COVID-19 strike globally. Bruce Gillen, a global health specialist with the Rockefeller Foundation’s Epidemic Prevention Initiative in New York City, asked at the meeting whether the annual update proposal implicitly required other countries to follow the FDA’s decisions. “Not necessarily,” answered Bill Falstich, vice president of global supply chain at vaccine maker Pfizer, which is based in New York City.
Although offering COVID-19 vaccines alongside flu shots can boost uptake, Gillen also questioned the plan to offer the updated vaccine in the US fall. During the pandemic, the United States has seen a wave of COVID-19 in the late summer as well as a significant increase in the winter, which may indicate that it is better to administer the vaccine earlier in the year, he says.
Peter Marks, chief of the Food and Drug Administration’s Biology Evaluation and Research Center in Silver Spring, Maryland, noted that giving the vaccine before the winter surge could prevent a rush in hospitalizations. In the winter, clinics are flooded with patients from the flu and respiratory syncytial virus (RSV), which has led to some US hospitals nearing capacity this season.
At the same meeting, the Vaccine Advisory Committee unanimously endorsed the agency’s proposal to adopt a single formulation of the COVID-19 vaccine for initial and booster doses. Currently, people in the US complete their initial series of COVID-19 vaccines – at least two doses of vaccines made by Pfizer – BioNTech, Moderna or Novavax, or one dose of Johnson & Johnson’s vaccine – all of which must then be followed by a booster dose after two months. As for the booster, Pfizer-BioNTech and Moderna initially provided an extra dose of their original vaccine, but the two companies now only offer “bivalent” boosters, which include more than one strain of SARS-CoV-2.
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The use of bivalent boosters was low in the United States: about 15% of eligible people received the bivalent vaccine. Some experts say this is because so many people have had a mixture of vaccines, which has led to confusion about what kind of booster they should get and when.
“We desperately need to streamline the vaccination schedule,” says Megan Raney, MD, a physician and public health specialist at Brown University in Providence, Rhode Island. “If we’re going to maintain our ability to vaccinate the country, we have to move toward a more standardized schedule, from a behavioral science point of view.” She adds that the proposal to adopt a single vaccine formulation for the entire series would alleviate some of this confusion, and may boost vaccine uptake because the vaccines could be offered alongside annual flu shots. “These changes make a lot of sense.”
Standardizing the vaccine formulation for the primary and booster series could mean that the bivalent vaccine will become the main formulation for people who have not yet had a primary series.
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The bivalent boosters currently in use in the US, UK and elsewhere target both the “ancestral” SARS-CoV-2 strain circulating at the start of the pandemic and the Omicron strain. Centers for Disease Control and Prevention (CDC) data shared at the advisory meeting shows that people ages 5 and older who only received one strain booster are twice as likely to die from COVID-19 than those who get a bivalent booster. . However, any booster still reduces the chances of an overall death from COVID-19.
Some members of the discussion group expressed concerns about the decision to use a bivalent formulation, rather than an updated single-strain formulation, in future vaccines. The scientists note that there is little data on the effectiveness of bivalent vaccines when given as a primary series — particularly in young children, who make up a large percentage of people now receiving the primary series in the United States. And some studies1And2 had hinted that the inclusion of the ancestral strain might impair the effectiveness of the vaccine against Omicron, due to a phenomenon called immunological fingerprint.
Marks indicated at the meeting that the advisory committee would meet again in May or June to discuss whether a change of formulation was warranted, and that the committee would then discuss whether the updated vaccine should include only one strain of SARS-CoV-2, or multiple . strains. That’s an important scientific question—but in the meantime, “especially if you’re older or have chronic illnesses, a booster is better than no booster when you’re in the middle of a surge,” says Rani.