Vaccines against the coronavirus are based on two different types of technology. The Pfizer and Moderna vaccines, which use mRNA technology, appear to be more effective than J&J, the new study reports.
Published by bioRxiv on Tuesday, the study examined blood samples in a laboratory setting. It is yet to be peer-reviewed.
However, the conclusions align with a similar study of the AstraZeneca vaccine – which, like J&J, is also adenoviral vector-based – that was released by the British government in May.
That study concludes one dose of the vaccine is 33 per cent effective against symptomatic disease of the Delta variant and 60 per cent effective against the variant after the second dose.
The new study suggests that the 13 million people who received the single dose J&J vaccine in the US may need to receive a second dose, ideally either of the Pfizer or Moderna vaccine.
It says: “While a single dose vaccination has advantages, the benefit provided by a second immunisation may be well worth the inconvenience.”
“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,” Nathaniel Landau, a virologist at New York University’s Grossman School of Medicine who led the study, told The New York Times.
The results contradict a study published by Johnson & Johnson at the beginning of the month that says a single dose of their vaccine is effective against the Delta variant and others, showing that the durability of the immune response lasts at least eight months.
A Johnson & Johnson representative told the Times that the data from the latest study “do not speak to the full nature of immune protection”.
The Independent has contacted the company for further comment.
The Delta variant now accounts for approximately 83 per cent of cases in the US, according to the Centers for Disease Control and Prevention.
No vaccine is 100 per cent effective, as the rise in breakthrough cases of Covid in vaccinated people demonstrates, but they have proven effective in preventing serious illness, hospitalisation, and death.