Study Finds mRNA COVID-19 Vaccines Have Stronger Initial Response, Ad26 Vaccine Remains More Stable Over Time

The Moderna COVID-19 vaccine elicited generally higher antibody responses that were also more durable compared to the Pfizer-BioNTech vaccine, according to a study published in the New England Journal of Medicine. The study compared the immune responses induced by 3 COVID-19 vaccines—Moderna, Pfizer-BioNTech, and Johnson & Johnson—and found that although the single-shot Johnson & Johnson vaccine induced lower initial antibody responses than the 2 mRNA vaccines, these responses were generally stable over time.

“Even though neutralizing antibody levels decline, stable T cell responses and non-neutralizing antibody functions at 8 months may explain how the vaccines continue to provide robust protection against severe COVID-19,” said Ai-ris Y. Collier, MD, a maternal-fetal medicine specialist at BIDMC, in a press release. “Getting vaccinated (even during pregnancy) is still the best tool we have to end the COVID-19 pandemic.”

The investigators evaluated and compared the immune responses induced by the 3 vaccines over the course of an 8-month follow-up period. The study included 61 participants and analyzed their levels of various antibodies, T cells, and other immune products, retrieving samples at 2 to 4 weeks following complete immunization and 8 months following vaccination. Thirty-one participants received the Pfizer-BioNTech vaccine, 22 received the Moderna vaccine, and 8 received the Johnson & Johnson vaccine.

“The mRNA vaccines were characterized by high peak antibody responses that declined sharply by month six and declined further by month 8,” said Dan H. Barouch, MD, PhD, director of the Center for Virology and Vaccine Research at BIDMC, in the release. “The single-shot Ad26 vaccine induced lower initial antibody responses, but these responses were generally stable over time with minimal to no evidence of decline.”

According to the investigators, these findings have important implications for understanding how vaccine immunity changes and wanes over time. They also emphasize that the precise immune responses necessary for an individual to receive protection against SARS-CoV-2 are not yet determined.

REFERENCE

Eight months later: Researchers compare immune responses elicited by three COVID-19 vaccines [news release]. EurekAlert; October 15, 2021. Accessed October 19, 2021. https://www.eurekalert.org/news-releases/931720