There are also some suggestions that the new subvariants have evolved to target the lungs—unlike Omicron, which usually resulted in a less dangerous infection of the upper respiratory tract…

The worst-case scenario is that BA.4 and BA.5 prove more capable of evading our antibodies than experts currently anticipate. Keep an eye on the hospitalization stats. If COVID hospitalizations start increasing in proportion to the growth in cases, it’s a sign the new sublineages are dodging our hard-won immunity.

In that case, a big spike in deaths is sure to follow.

That could be a big red flag for the Americas. COVID variants tend to travel from east to west, globally. New variants and subvariants tend to appear in the United States a few weeks after becoming dominant in the U.K. At present, BA.4 and BA.5 account for just a fifth of new cases in the U.S. Expect that proportion to increase.

The problem for Americans is that they’re much less protected than Britons. Yes, Americans have a lot of antibodies from past infection, but they’re also a lot less likely to be vaccinated—and even less likely to be boosted. Just 67 percent of Americans are fully vaxxed. A little over a third of the U.S. population has gotten a booster.