Tweaked COVID boosters close but how much will they help?

COVID-19 vaccines tweaked to better match today’s omicron threat are expected to roll out in a few weeks but still up in the air is how much benefit the booster shots will offer, who should get one -- and how soon.

Pfizer and rival Moderna both asked U.S. regulators this week to authorize modified versions of their booster vaccine — shots that are half the original recipe and half protection against BA.4 and BA.5, the newest versions of omicron.

The Food and Drug Administration ordered that recipe at the end of June, and now has to decide if this combination -- what scientists call a “bivalent vaccine” -- is ready.

The Biden administration hopes updated boosters could help blunt a winter COVID-19 surge in a population weary of the virus — and of vaccinations. But while the first-ever modification to these vaccines is momentous, it's more of an expected next step — like how flu vaccines get updated every year — than a true next-generation shot.

“We need to give a clear, forward-looking set of expectations,” said University of Pennsylvania immunologist E. John Wherry, who compares vaccine tweaks to periodically updating your computer software.

WHY DID FDA ORDER COMBO SHOTS?

BA.5 currently is causing nearly all COVID-19 infections in the U.S. and much of the world. Current COVID-19 vaccines match the coronavirus strain that circulated in early 2020. And while those vaccinations still offer strong protection against serious illness or death from COVID-19, there’s little effectiveness against infection from the wildly mutated omicron family.

The gamble is that BA.5, or something similar, still will be circulating when cold weather hits so the combo shots will be a good match. (Vaccines target the spike protein that coat the coronavirus, and the BA.4 and BA.5 spikes are...