Infections are falling as Delta fades, but the newer strain is spreading fast. If we can’t stomach a lockdown, we need to vaccinate the other 75% of the planet.

(Originally published Sept. 7 in “What in the World“) The Mu strain of Covid-19 appears to be spreading fast, and is now in 49 U.S. states—up from a reported three just a day before—and in 39 countries. It still only represents 1% of all U.S. cases so far, and still no word on how well vaccines work against it, so stay tuned.

In the meantime, the overall surge brought to you by the Delta strain is ebbing fast, but not fast enough to stop a fall rollback in summer reopening by businesses. With nationwide infections quadruple the level a year ago, the U.S. is on track to start by Sept. 20 offering booster shots to those who received Pfizer vaccines. Those who received Moderna or Johnson & Johnson will have to wait longer. The U.S. Food and Drug Administration is fortunate enough to have the nation of Israel as its guinea pig: the Israelis have already been doling out boosters and will share their results with the U.S. If all goes well and Mu doesn’t prove elusive to existing vaccines, however, we could see a resumption of reopening measures by November.

Boosters in the U.S. and elsewhere in the wealthy world won’t do much to help the roughly 5.8 billion people who haven’t yet been vaccinated. The G20 has jumped on the vaccine inequity bandwagon, calling for rich nations to do more to get vaccines to the rest of the world. The “jab the world” song seems to have fallen off the hit parade since Delta’s resurgence across the developed world. But Germany’s health minister, Jens Spahn, was absolutely correct when he pointed out that “the pandemic is only over when infections subside worldwide, pointing to the dangers of variants emerging in unvaccinated hot spots spreading elsewhere.”