One Dose of J.&J. Vaccine Is Ineffective Against Delta, Study Suggests

According to results from a laboratory study posted online on Tuesday, Johnson & Johnson's COVID-19 vaccine is much less effective against the Delta and Lambda variants than against the original virus, The New York Times reported.

"The message that we wanted to give was not that people shouldn't get the Johnson & Johnson vaccine, but we hope that in the future, it will be boosted with either another dose of Johnson & Johnson or a boost with Pfizer or Moderna,"  said study lead Nathaniel Landau.

Johnson & Johnson spokeswoman Seema Kumar said that the data "do not speak to the full nature of immune protection," adding that studies sponsored by the company indicate that the vaccine "generated strong, persistent activity against the rapidly spreading Delta variant."

The researchers looked at blood samples taken from 17 people who had been immunised with two doses of an mRNA vaccine and 10 people with one dose of Johnson & Johnson's vaccine.

Johnson & Johnson's vaccine started out with a lower efficacy than the mRNA vaccines and showed a larger drop in efficacy against the Delta and Lambda variants.

While the FDA has said that people who are "fully vaccinated do not need a booster shot at this time," Landau noted that the new data should prompt the agency to revisit its recommendations.