Moderna or Pfizer booster works best for J&J vaccinated, study finds

People who received the Janssen vaccine against COVID-19 from Johnson & Johnson (J&J) they may benefit from a booster dose of Pfizer or Moderna, preliminary results of a US study showed.

The study, funded by the National Institutes of Health (NIH), was eagerly awaited in the United States because it looked at the possibility of “mixing” vaccines, using a different vaccine than the starting doses for the booster vaccine, which is currently not allowed in the country.

The study was conducted in 458 adults who had been vaccinated with one of the three approved brands in the United States (Pfizer, Moderna or J&J) for at least 12 weeks.

Each of these three groups was divided into three new groups to receive one of the available vaccines as a booster. The nine groups were made up of about 50 people each.

The researchers then tested the antibody levels 15 days after the booster shot.

For people initially inoculated with J&J, antibody levels were four times higher after a boost from J&J, 35 times higher after a boost from Pfizer, and 76 times higher after a boost from Moderna.

And antibody levels for those who had originally received Moderna injections were higher “regardless of the booster shot administered,” compared to those who had initially received Pfizer or J&J, according to the study.

Furthermore, “no safety concerns were identified” after the booster doses were administered.

However, the study, which has not yet been peer-reviewed, has several limitations. The number of participants was small and the immune response could evolve over time, beyond the 15 days observed during the study.

“It is important not to get too carried away by the findings,” tweeted Peter Hotez, a professor at Baylor College of Medicine.

The test results of a second J&J booster injection conducted by the company itself were “impressive,” he said.

The NIH study should prompt discussions by a committee of experts from the US Food and Drug Administration (FDA), which is scheduled to consider requests for booster doses from Moderna and J&J on Thursday and Friday, respectively.

A Pfizer booster has already been approved in the United States for certain populations, such as people 65 and older, adults with high-risk medical conditions, and those in jobs where they are frequently exposed to the coronavirus.