In the past two weeks, many medical experts started to question whether the Johnson & Johnson vaccine, which is administered in a single dose, would be as effective as the two-dose Pfizer-BioNTech or Moderna vaccine in protecting against the new, highly transmissible delta variant that is poised to become the dominant strain in the U.S.
The reason for their doubts were studies showing that the J&J vaccine was less effective at preventing disease than the other two vaccines and also less protective against variants. In recent days, several scientists and even members of the public who originally got J&J decided to get a “booster dose” of an mRNA vaccine, Pfizer-BioNTech or Moderna, to bolster their immune systems.
But data released Thursday night by Johnson & Johnson showed that the vaccine remains highly protective against the delta variant and immunity may be long-lasting.
“Those who got J&J should be less worried than they may have been before about delta,” said Dr. David Diemert, a professor of medicine at George Washington University who was not involved in J&J’s research. “It is reassuring.”
The Food and Drug Administration granted the J&J vaccine emergency use authorization in February on the heels of the Pfizer-BioNTech and Moderna vaccines. After a 10-day pause in April, triggered when the vaccine was found to be associated with rare but severe blood clots, distribution resumed. About 12 million Americans have received it so far.
Experts say the delta variant, first identified in India, is 40% to 60% more transmissible than other variants, meaning that unvaccinated people can more easily catch covid-19 and that those who have been vaccinated face a higher risk of breakthrough infections. The delta variant has also been associated with greater disease severity than other variants. In the U.S., it now accounts for about 25% of covid cases.
The Johnson & Johnson data released Thursday offered the first window into how well the J&J shot holds up against the delta variant.
“We believe that our vaccine offers durable protection against COVID-19 and elicits neutralizing activity against the Delta variant,” Dr. Paul Stoffels, chief scientific officer at Johnson & Johnson, said in a press release.
The data comes from two small-sample preprint studies, which have not yet been peer reviewed and were both conducted in laboratories.
One of the new studies showed that the J&J vaccine continued to produce a high number of antibodies in the presence of the delta variant. And the number was actually higher than what recent data had shown for antibody levels against the beta variant (first identified in South Africa).