TThe Covid-19 vaccines are on track for a major prescription change this fall.
Today’s vaccines still contain the original coronavirus strain, the one that caused the pandemic – even though it was long ago replaced by mutated versions as the virus rapidly evolves.
On Thursday, the Food and Drug Administration’s scientific advisers said the next round of shots in the US should only include protections against the newest variants that are now globally dominant – a branch of the Omicron family tree called XBB.
The FDA will make the final decision. Vaccine makers said at the meeting that they could have updated vaccines available within months, depending on the strain.
While the number of infections has declined, the virus could be a real concern over the coming winter, FDA vaccine chief Peter Marks said as the daylong meeting began.
“We are concerned that we will have another wave of COVID-19 at a time when the virus has continued to develop, the immunity of the population has further declined and we are moving indoors for the winter,” he said.
Here are some things you should know:
WHY ANOTHER ROUND OF SHOT?
The FDA had told Americans to expect an updated fall vaccine against Covid-19, just as they get a new flu shot every fall. Although most of the population is infected or has had at least one round of vaccination, the coronavirus continues to bring new variants to the market.
What is now being used in the US are combination shots from Pfizer and Moderna that combine the original strain with protection against last year’s most common omicron variants, called BA.4 and BA.5. But only 17% of Americans rolled up their sleeves for a combo booster.
And while the FDA this spring allowed seniors and others at high risk to receive an additional booster dose, by the fall most people will be many months past their last shot.
The currently available recordings still help prevent serious illness and death, even as XBB variants have taken over. But the protection gradually diminishes over time and was short-lived against milder infections, even before the virus inevitably evolved again.
SHARPENING PROTECTION
Last year, as regulators struggled to decide how to update the vaccine, a combo shot seemed like the safest bet. Omicron was fairly new and there was no way of knowing how long it would last or if the next big change in the coronavirus would be more like the original strain.
Preserving the original tension in the recording actually has a downside called ‘imprinting’. After repeated exposure to the original strain, the people’s immune systems tended to recognize it and react more strongly to it than to half the new booster dose that was brand new.
So the FDA is leaning towards choosing a fall shot prescription that only targets XBB. The hope is that the XBB variants are different enough to trigger the immune system to make more diverse, cross-protective virus-fighting antibodies.
The World Health Organization’s vaccine advisers and European regulators have recently issued similar recommendations.
FORECAST WHAT WILL LEAVE THIS WINTER
Another challenge: deciding which XBB variant to target – since what’s spreading now will probably have mutated again by winter.
Regulators will make their best guess, just as they do every year when determining the fall flu vaccine prescription.
The FDA has identified three XBB subtypes as top grades. Vaccine makers have already developed XBB-targeted formulas.
HOW MANY MORE SHOT?
Older adults and others at high risk due to severely weak immune systems still have the highest hospitalizations from Covid-19, even though cases have declined. One question is whether they are urged to get a single trap shot or qualify for more than one.
Another is how many doses the youngest children who have never been vaccinated would need.
Ultimately, the Centers for Disease Control and Prevention will make the final recommendations.
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The Associated Press Health and Science division is supported by the Science and Educational Media Group of the Howard Hughes Medical Institute. The AP is solely responsible for all content.