Why COVID-19 boosters weren’t tweaked to better match variants
More COVID-19 booster shots might be on the way — but when it’s your turn, you’ll get an extra dose of the original vaccine, not one updated to better match the extra-contagious delta variant.
And that has some experts wondering if the booster campaign is a bit of a missed opportunity to target delta and its likely descendants.
“Don’t we want to match the new strains that are most likely to circulate as closely as possible?” Dr. Cody Meissner of Tufts Medical Center, an adviser to the Food and Drug Administration, challenged Pfizer scientists recently.
“I don’t quite understand why this is not delta because that’s what we’re facing right now,” fellow adviser Dr. Patrick Moore of the University of Pittsburgh said last week as government experts debated whether it’s time for Moderna boosters. He wondered if such a switch would be particularly useful to block mild infection.
The simple answer: The FDA last month approved extra doses of Pfizer’s original recipe after studies showed it still works well enough against delta — and those doses could be rolled out right away. Now, the FDA is weighing evidence for boosters of the original Moderna and Johnson & Johnson vaccines.
“It’s less churn and burn on the manufacturing” to only switch formulas when it’s really necessary, said FDA vaccine chief Dr. Peter Marks.
But Pfizer and Moderna are hedging their bets. They’re already testing experimental doses customized to delta and another variant, learning how to rapidly tweak the formula in case a change is needed for today’s mutants or a new one.
What we know so far:
CURRENT VACCINES WORK AGAINST DELTA
Vaccines used in the
U.S. remain strongly effective against hospitalization and death from COVID-19, even after the delta variant took over, but authorities hope to shore up waning protection against less severe infection and for high-risk populations. Studies show an extra dose of the original formulas revs up virusfighting antibodies that fend off infection, including antibodies that target delta.
MIGHT A DELTA-SPECIFIC BOOSTER WORK BETTER?
Vaccines target the spike protein that coats the coronavirus. Mutations in that protein made delta more contagious but to the immune system, it doesn’t look all that different, said virus expert Richard Webby of St. Jude Children’s Research Hospital.
That means there’s no guarantee a delta-specific booster would protect any better, said University of Pennsylvania immunologist John Wherry. Waiting for studies to settle that question — and if necessary, brewing updated doses — would have delayed rolling out boosters to people deemed to need them now.
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