But there’s a possible mix of jabs that may—with careful study—ultimately prove even more effective: a dose of Johnson & Johnson’s conventional, adenovirus-based vaccine combined with a high-tech mRNA jab from Pfizer or Moderna. Multiple early studies in Europe focused on the AstraZeneca shot, which is similar to the J&J, have found that an adenovirus “prime,” or initial shot followed by an mRNA booster, might provoke the strongest and most enduring immune response yet to the coronavirus…

Meanwhile, some studies have indicated that the Moderna vaccine creates a stronger immune response than the Pfizer vax, especially against the Delta variant. Inasmuch as that may be true, and in light of what initial European studies have been finding, the best possible vaccine mix in the United States may prove to be Johnson & Johnson plus Moderna, Klausner suggested.

But Johnson & Johnson plus Pfizer could be pretty good, too. Gostin, for his part, said he expects the FDA to eventually authorize Americans to combine Johnson & Johnson with either one of the mRNA vaccines.

“That seems a highly likely result in the U.S,” he said.