J&J vaccine may be less effective against Delta, study suggests

• The coronavirus vaccine made by Johnson & Johnson is much less effective against the Delta and Lambda variants than against the original virus, according to a new study posted online on Tuesday.
• Although troubling, the findings result from experiments conducted with blood samples in a laboratory, and may not reflect the vaccine's performance in the real world. But the conclusions add to evidence that the 13 million people inoculated with the J&J vaccine may need to receive a second dose - ideally of one of the mRNA vaccines made by Pfizer-BioNTech or Moderna, the authors said.
• The conclusions are at odds with those from smaller studies published by Johnson & Johnson earlier this month suggesting that a single dose of the vaccine is effective against the variant even eight months after inoculation.
• The new study has not yet been peer reviewed nor published in a scientific journal. But it is consistent with observations that a single dose of the AstraZeneca vaccine - which has a similar architecture to the J&J vaccine - shows only about 33% efficacy against symptomatic disease caused by the Delta variant.
• 'The message that we wanted to give was not that people shouldn't get the J&J vaccine, but we hope that in the future, it will be boosted with either another dose of J&J or a boost with Pfizer or Moderna,' said Nathaniel Landau, a virologist at NYU's Grossman School of Medicine, who led the study.
• Other experts said the results are what they would have expected, because all of the vaccines seem to work better when given in two doses. 'I have always thought, and often said, that the J&J vaccine is a two-dose vaccine,' said John Moore, a virologist at Weill Cornell Medicine in New York.
• Dr Moore pointed to several studies in monkeys and people that have shown greater efficacy with two doses of the J&J vaccine, compared with one dose. He said the new study was particularly credible because it was published by a team with no ties to any of the vaccine manufacturers.
• But the data from the new study 'does not speak to the full nature of immune protection,' said Seema Kumar, a spokesperson for J&J. Studies that have been sponsored by the company indicate that the vaccine 'generated strong persistent activity against the rapidly spreading Delta variant,' she said.
• The Delta variant is the most contagious version yet of the coronavirus. It accounts for 83% of infections in the United States, Dr Rochelle Walensky, director of the Centers for Disease Control and Prevention, said at a Senate hearing on Tuesday.
• The variant may also be mainly responsible for a recent rise in infections. Although they are still low relative to last winter, cases are rising in all 50 states, and hospitalizations are increasing in nearly all of them. In the two weeks ending on Tuesday, the nation averaged 268 deaths per day. 
• Delta may cause more breakthrough infections than earlier forms of the virus, but more than 99% of the hospitalizations and deaths are occurring among unvaccinated people. Rates of immunization in the country have stalled, with just under 60% of adults fully protected against the virus.
• Several studies have suggested that the mRNA vaccines made by the Pfizer-BioNTech and Moderna will maintain their efficacy against the coronavirus, including all variants identified so far. One recent study showed, for example, that the vaccines trigger a persistent immune reaction in the body that may protect against the coronavirus for years.
• But evidence on the J&J vaccine has been limited, because it was rolled out later than the mRNA vaccines, Most studies of effectiveness of the coronavirus vaccines were conducted at medical centers and hospitals that relied on staff members who received the mRNA vaccines.

New York Times - 20 July 2021