Home Uncategorized US experts debate how to update COVID-19 vaccines

US experts debate how to update COVID-19 vaccines


WASHINGTON (AP) — More than two years into the COVID-19 pandemic, U.S. health officials are beginning to grapple with how to keep vaccines up to date to better protect Americans against the ever-evolving coronavirus.

On Wednesday, a group of Food and Drug Administration vaccine advisers spent hours debating key questions for revamping vaccines and conducting future booster campaigns. They did not come to any definitive conclusions.

Questions experts faced included: how often vaccines against new strains should be updated, how effective they are in warranting approval, and whether updates should be coordinated with global health authorities.

Last week, the FDA authorized a fourth dose of the Pfizer or Moderna vaccines for anyone 50 or older and for some younger people with severely weakened immune systems. It is an effort to get ahead of another possible push.

But the FDA’s head of vaccines, Dr Peter Marks, acknowledged at the meeting “we just can’t stimulate people as often as we are.” He called the latest recall update a “stop-gap” measure to protect vulnerable Americans while regulators decide if and how to modify current vaccines.

Marks warned that declining vaccine protection, new variants and colder weather in the fall could increase the risk of further outbreaks.

“Our goal here is to stay ahead of future variants and outbreaks and to ensure that we do our best to reduce the number of illnesses and deaths from COVID-19,” Marks said, adding that expects more vaccine panel meetings in the coming months. .

Some of the key questions addressed by the panel:


One area where experts seemed to agree is that vaccines should be judged on their ability to prevent serious illnesses that lead to hospitalization and death.

“We need to focus on the worst case scenario, which is severe disease, and we need to switch strains when we lose that battle,” said Dr Mark Sawyer of the University of California, San Diego.

By this measure, current vaccines have held up remarkably well.

During the last omicron-induced surge, two doses of the vaccine were nearly 80% effective against needing a respirator or dying – and a booster boosted that protection to 94%, researchers recently reported. federal scientists.

But only about half of Americans eligible for a third shot got one. And many experts have said it’s unsustainable to keep asking Americans to get boosts every few months.

A panelist from the Centers for Disease Control and Prevention suggested that 80% protection against severe disease could become the standard for evaluating vaccines.

“I think we may have to accept that level of protection and then use other alternative means to protect individuals with therapies and other measures,” said CDC chief medical officer Dr. Amanda Cohn.

Presentations at the meeting by government health officials and independent researchers highlighted the challenges of predicting when the next major variant of COVID-19 might appear.

Trevor Bedford, disease modeler at Fred Hutchinson Cancer Research Center, said a major new strain like omicron could emerge every 1.5 years to once a decade, based on currently available data. Given this unpredictability, researchers will need methods to quickly determine whether current vaccines work against emerging variants.


The three COVID-19 vaccines currently in use in the United States are based on the original version of the coronavirus that emerged in late 2019. Updating vaccines will be a complex task, likely requiring coordination between the FDA, manufacturers and global health authorities .

To speed vaccines to market, the FDA has relied on research shortcuts to judge effectiveness, primarily looking at their early impact on immune system antibody levels. A number of panelists said Wednesday they want more rigorous data from studies that follow patients over time to see who gets sick or dies.

But this approach would probably take too long.

“We face a conundrum in that it will be difficult to generate all the data we want in a short time when a new variant emerges,” said Dr Ofer Levy of Harvard Medical School.

A representative from the US Biomedical Advanced Research and Development Authority outlined the narrow window manufacturers could face to reformulate, study and mass-produce an updated vaccine by September.

“If you’re not on your way to a clinical trial in early May, I think it’s going to be very difficult to get enough products out of the manufacturers to meet the demand,” said Robert Johnson, BARDA Deputy Assistant Secretary. .

The annual flu vaccine update process offers a possible model, as presented by a representative of the World Health Organization.

Twice a year, WHO experts recommend flu vaccine updates to target emerging strains. The FDA then takes those recommendations to its own vaccine panel, which votes on whether they make sense for the United States, paving the way for manufacturers to tweak their vaccines and begin mass production.

But COVID-19 has not yet fallen into a predictable flu-like pattern. And as the coronavirus evolves, different strains may become dominant in different parts of the world.

Several experts said they would need more meetings with more data and proposals from the FDA to decide on a strategy.

“We had never been here before. We’re all working together to do our best and it’s very complex,” said Oveta Fuller of the University of Michigan Medical School.


The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute Department of Science Education. The AP is solely responsible for all content.