Mixing COVID-19 Vaccine Boosters Increases Immune Response

Yesterday, the National Institutes of Health (NIH) released a study showing that people vaccinated with one of the three COVID-19 shots authorized in the US (Janssen/Johnson & Johnson, Pfizer-BioNTech, and Moderna, inc.) could reap more benefits by getting a different booster dose than their original vaccine.

According to the study, “boosting with any of the three vaccines currently licensed or authorized for emergency use in the US will stimulate an anamnestic response in persons who previously received of the primary series of any of these vaccines. Homologous boosts provided a wide range of immunogenicity responses, with heterologous boosts providing comparable or higher titers.”

The investigators enrolled 458 participants in the study and divided them into two age groups, 18-55 years and 56 years and older. A relatively equal number of participants received each of the three Emergency Use Authorization (EUA) vaccines, and either a homologous or heterologous booster dose four to six months later.

The results showed that a heterologous booster dose of any of the three EUA vaccines led to a significantly greater immune response. However, an mRNA booster of Pfizer-BioNTech or Moderna spiked antibody levels noticeably higher than the Johnson & Johnson booster. Participants who originally received a Johnson & Johnson vaccine had lower antibody levels before the study, so they experienced a major spike after receiving the mRNA booster.

These findings, that receiving a different booster is not only safe but more effective, are vital; the accessibility of certain COVID-19 vaccines differs by time and region, so the potential to receive a booster of whichever vaccine is available is an important step toward building herd immunity.

So far, only the Pfizer-BioNTech vaccine is approved for boosters (for certain high-risk populations). However, the FDA Vaccines and Related Biological Products Advisory Committee (VRBPAC) is meeting today to discuss possible approval of the Moderna booster dose, and tomorrow to discuss Johnson & Johnson.