STRANGE NEW RESPECT: As Virus Data Mounts, the J.&J. Vaccine Holds Its Own: Once dismissed as less effective, the vaccine now seems to be preventing infections and illness about as well as the two mRNA options.

Roughly 17 million Americans received the Johnson & Johnson Covid vaccine, only to be told later that it was the least protective of the options available in the United States. But new data suggest that the vaccine is now preventing infections, hospitalizations and deaths at least as well as the Pfizer-BioNTech and Moderna vaccines. . . .

Until last June, the cumulative data from the C.D.C. showed that immunization with the Moderna vaccine resulted in the lowest rates of breakthrough infections; those who got Johnson & Johnson saw the highest rates, with Pfizer-BioNTech somewhere in the middle.

During the summer months, the gaps — particularly between J.&J. and Pfizer — began to narrow. By now, all the vaccines seem to be performing about equally well against coronavirus infections; in fact, Johnson & Johnson appears to be holding up slightly better.

None of the vaccines has lived up to the initial hopes. They’re not worthless, but they’ve underperformed.