Scientists are split about US FDA proposal to update COVID-19 vaccines once a year, similar to agency’s approach for annually updating influenza vaccines.
Scientists are split about a US Food and Drug Administration’s (FDA) proposal to update COVID-19 vaccines once a year, similar to the agency’s approach for annually updating influenza vaccines. At a meeting of the FDA’s vaccine advisory panel on 26 January, some researchers argued that the proposal to offer an updated vaccine every US autumn would help simplify the country’s complex COVID immunization schedule and might boost uptake as a result.
But other scientists were less convinced about the timeline — or whether healthy adults should be urged to receive an annual COVID-19 jab at all. Angela Shen, a vaccine specialist at Children’s Hospital of Philadelphia in Pennsylvania, says the FDA proposal, released on Monday, is “conceptually not a bad idea”. But she questions whether the data support updating the vaccine composition once a year because SARS-CoV-2 spawns new variants at a much faster rate than influenza.
“Just scratching out ‘flu’ and replacing it with ‘COVID’ on all the documents might not work, because COVID is not the flu,” says Shen, who is a member of a US Centers for Disease Control and Prevention advisory panel on immunization practices.
The timeline for updating flu jabs is based on the well-documented seasonal pattern for the emergence of new influenza strains: selection of strains for Northern Hemisphere vaccines are based in part on which strains spread widely during the previous Southern Hemisphere winter. Although there is some evidence that SARS-CoV-2 also spreads seasonally, that pattern is not as predictable as influenza.
“We understand the seasonality of flu, and know exactly when to vaccinate for optimal effect,” says Luciana Borio, a former acting chief scientist at the FDA, who is now a global-health specialist at the Council on Foreign Relations in New York City. But “we simply do not know whether people need to be vaccinated every year or less frequently to be protected from severe COVID”.
Additionally, SARS-CoV-2 variants don’t sweep the world as uniformly as they do for influenza, which means it will be difficult to coordinate the composition of a COVID-19 jab globally.
Bruce Gellin, a global-health specialist at The Rockefeller Foundation’s Pandemic Prevention Initiative in New York City, asked at the meeting if this FDA proposal to update vaccine formulation annually would implicitly require that other countries worldwide follow the FDA’s decisions. Bill Falstich, vice president for global supply chain for vaccine-manufacturer Pfizer, responded at the meeting, “Not necessarily.”
Although the benefits of offering an updated COVID-19 vaccine alongside influenza vaccines in the fall could potentially boost uptake, Gellin also questioned the plan to offer an updated vaccine in the US autumn. There has been a late-summer COVID-19 surge in addition to a larger winter surge for the past few years in the United States, which could suggest giving the vaccine earlier in the year, he says.
But timing the jab prior to the winter surge could allay a surge of hospitalizations, noted Peter Marks, the head of FDA’s Center for Biologics Evaluation and Research in Silver Spring, Maryland. During winter, clinics are swamped with people infected with influenza and RSV, which led to some US hospitals nearing capacity this year.
At the same meeting, the vaccine advisory panel unanimously endorsed the FDA proposal to adopt a single COVID-19 vaccination composition for both the primary and booster series. Currently, people in the United States complete a primary COVID-19 vaccination series – at least two doses of Pfizer-BioNTech, Moderna or Novavax vaccines, or a single jab of a Johnson & Johnson vaccine – all of which should then be followed by a booster shot two months later.
For this booster, Pfizer-BioNTech and Moderna first offered an additional dose of its original vaccine, but now the companies offer only a ‘bivalent’ booster, which includes more than one strain of SARS-CoV-2.
Uptake of the bivalent booster has been low in the United States: about 15% of eligible people have received the two-strain jab. Some experts say that is because many people have received a mixture of vaccines, which has led to confusion over which type of jab they should receive and when.
“We desperately need to simplify the vaccination schedule”, says Megan Ranney, a physician and public-health specialist at Brown University in Providence, Rhode Island. “If we’re going to sustain our ability to vaccinate the country, we have to move toward a more standardized schedule from a behavioural science point-of-view.”
The proposal would alleviate some of that confusion, and it might boost vaccine uptake because they might be offered alongside annual influenza vaccines, she adds. “These changes make a lot of sense.”
Standardizing vaccine composition for both the primary and booster series would probably mean the bivalent vaccine will become the formulation for people who haven’t received a primary series yet.
The current bivalent boosters used in the United States, the United Kingdom and elsewhere target both the ‘ancestral’ SARS-CoV-2 strain circulating at the start of the pandemic and an Omicron strain. US Centers for Disease Control and Prevention data show that people 5 and older who were vaccinated with a single-strain booster were twice as likely to die from COVID-19 as those who received a bivalent booster.
But some panellists at the meeting had concerns about the decision to use a bivalent formulation in future vaccines, instead of an updated single-strain one. Scientists noted that there is limited data for effectiveness of the bivalent vaccine as a primary series, particularly in young children, who make up a significant portion of the people receiving a primary series today.
And some studies have hinted that including the ancestral strain might blunt the vaccine’s effectiveness against Omicron because of a phenomenon called immune imprinting.
Marks noted at the meeting that the advisory panel would convene again in May or June to discuss if a change is warranted to the COVID-19 vaccine formulation, and that the panel would then tackle if an updated vaccine should include just one strain, or multiple strains of SARS-CoV-2.
This is an important scientific question to understand, Ranney says, but in the meantime, “especially if you’re older or have chronic conditions, a booster is better than no booster when you’re in the middle of a surge”, she adds.
Originally published at Nature