Once health officials made it clear that the world would need a booster dose of the COVID-19 vaccine, they needed to know if people could mix doses of vaccines from different manufacturers.
In the first to learn To provide results on such cross-dosing, researchers say it is safe for people who have received any of the three vaccines available in the US to receive a booster dose of another – and that they found early evidence that certain Combinations can elicit stronger immune responses than others. The study, published on a preprint server and not yet peer-reviewed, came the same day the Food and Drug Administration (FDA) convened a panel of external experts to review Moderna’s application for a booster vaccination. The FDA and Centers for Disease Control have granted emergency approval for Pfizer-BioNTech’s booster, but are currently reviewing data on the safety and effectiveness of Moderna and J&J boosters.
For the mix-and-match study, the researchers looked at 458 people who were originally vaccinated with Pfizer BioNTech, Moderna, or Johnson & Johnson-Janssen vaccines and then randomly assigned one of the three booster doses about four to six months later. It was not designed to directly compare the immune responses of one booster with another, but rather to give researchers a comprehensive sense of whether the antibody responses produced were overall similar for all three boosters – for example, to see if people were having the originally received Pfizer®, – BioNTech’s vaccine produced similar immune responses after receiving an additional dose of a Pfizer BioNTech, Moderna, or J & J’s shot.
In general, people who received a booster vaccine with a different vaccine than the one originally received had antibody increases that were similar or higher than those who received a different dose of the same vaccine from their first vaccination (s). There were small differences, however. Individuals who received the J&J individual vaccine had higher jumps in neutralizing antibodies after a booster dose of the Pfizer BioNTech or Moderna vaccine compared to another dose of the J&J vaccine: 50-fold for the former two vs. 5 fold in the latter. It’s not clear why, but it could be related to J & J’s vaccine being based on a different technology from that of Pfizer-BioNTech and Moderna.
The J&J Shot uses an adenovirus vector to deliver viral genes to the immune system, which then recognizes them as foreign and triggers an attack, while Pfizer-BioNTech and Moderna vaccines use new technology to capture the mRNA form of the genetic SARS-CoV-2 to deliver material directly. And there is some early evidence that different technologies may induce different types of immunity – for example, some preliminary data suggests that J & J’s vaccine may be more effective at addressing T-cell-based responses that may be more permanent, amplified faster and able to recognize new variants than the highly antibody-based responses that Moderna and Pfizer-BioNTech initially generate. The FDA will consider such data when evaluating booster vaccinations from Moderna and J&J Janssen on October 14-15.
The results are encouraging as they suggest that it is safe for providers to combine dosages when it comes to boosters. Public health experts have spoken out in favor of anyone immunized against COVID-19 getting a booster shot to combat the diminishing protection afforded by the vaccines in the face of the faster-spreading Delta variant, and the option of one of the three vaccines this will ensure more people will get the extra shot.
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