'Worst version of COVID' will be dominant in U.S. by July

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For the last 18 months, the original COVID-19 vaccines — first as a two-dose series, then as boosters — have done an extraordinary job shielding us from illness, hospitalization and death. Globally, they saved nearly 20 million lives in 2021 alone. Even today, unvaccinated Americans are twice as likely as vaccinated Americans to test positive for COVID — and six times as likely to die from the disease.

But viruses evolve, and vaccines should too.

That was the big-picture takeaway from a pivotal meeting this week of the U.S. Food and Drug Administration’s expert advisory panel. The question before them was simple: Ahead of an expected winter surge, should vaccine manufacturers tweak their forthcoming booster shots to target Omicron — the ultra-infectious variant that has spent the last seven months surging throughout the world in one form or another — or should they stick with the tried-and-true 2020 recipe?

The panel voted 19-2 on Tuesday in favor of Omicron boosters. The question now, however, is which version of Omicron the next round of shots should target.

For anyone who hasn’t been paying attention, the Omicron strain that triggered last winter’s massive COVID wave (BA.1) is now extinct. In March, it was supplanted by the even more transmissible BA.2 … which was supplanted in May by the even more transmissible BA.2.12.1 … which is now being supplanted by the (you guessed it) even more transmissible BA.4 and BA.5.

Experts say BA.5 is the one to worry about: “The worst version of the virus that we’ve seen,” as Dr. Eric Topol, the founder of Scripps Research Translational Institute, recently put it. Together, the closely related BA.4 and BA.5 now account for the majority of new U.S. COVID cases, according to the latest data from the Centers for Disease Control and Prevention — but BA.5 (36.6%) is spreading a lot faster than BA.4 (15.7%). By early July, it will be the dominant strain in the U.S.

That’s troublesome for several reasons. To our immune system, the distance from BA.1 to heavily mutated BA.4 and BA.5 is “far greater,” Topol writes, than the distance from the original BA.1 virus to previous blockbuster variants such as Alpha and Delta — which makes them harder to recognize and respond to.

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