President Joe Biden said that Texas Gov. Greg Abbott made a “big mistake” last month when he eliminated mandated masks and ended capacity restrictions on businesses. Nevertheless, new COVID virus cases there have decreased 24 percent in the past two weeks.

That’s completely baffling to some New Yorkers, who, despite still diligently covering their faces in public and observing capacity limits nearly everywhere, have seen virus cases statewide shoot up 33 percent in the past 14 days — the third-highest rate of new infections in the country, behind Michigan and New Jersey.

What gives?

Don’t listen to know-nothings who insist, against all evidence, that masks and social distancing don’t work. They do. But in other parts of the country, vaccinations are outpacing the virus’ spread. In New York, we’re facing new, even more contagious, mutated variations of the virus, which are spreading as fast if not faster than we’re able to get out shots, especially among young people who have just become eligible. That’s not translating into rising hospitalizations and deaths, but it is fueling new infections.

City health officials tell us two super-contagious mutant strains, the “New York” variant, labeled B.1.526, and the “U.K.” variant, B.1.1.7, now make up half of all of New York’s new COVID cases. The vaccines are working, though, both against plain-old SARS-CoV-2 and its new cousins. Since early February in New York City, when vaccines became widely available to the elderly, COVID infection rates among people age 65 and over, the likeliest to die from the disease, have been cut in half. That’s why fewer people are needing serious medical treatment and dying.

But just because deaths have gone down is no reason to rest easy. So long as variants keep spreading they’ll keep mutating, evolving new defenses that eventually could render useless our miraculous vaccines. The Biden administration should consider sending extra doses to hot spots like New York now battling the variants. If this is a war, surge defenses where the threat is largest.