Mixing Vaccines Boosts COVID-19 Immunity

By Reuters Staff

January 28, 2022

(Reuters Health) - Mixing vaccines may slightly increase the effectiveness of immunization against COVID-19, according to findings from a study of 458 U.S. patients who received booster shots.

The test looked at booster shots using the Pfizer, Moderna and Johnson & Johnson vaccines, and results are published in the New England Journal of Medicine.

When the booster was the same product as the original vaccine, neutralizing antibody titers increased by a factor of 4 to 20, but when a different product was used for the booster, that increased titers by a factor of 6 to 73.

The only combination that didn't result in an increase in spike-specific T-cell responses was among patients who only received the Johnson & Johnson vaccine as primary vaccine and booster.

However, CD8+ T-cell levels were more durable in patients primed with the Johnson & Johnson vaccine, and using that product as a booster "substantially increased spike-specific CD8+ T cells in the mRNA vaccine recipients," writes the team led by Dr. Robert Atmar of the Baylor College of Medicine in Houston.

"Thus, the heterologous boost immunization strategy provides an immune response that may prove to be beneficial for durable prevention and control of Covid-19," they write.

Whether the vaccination regimen included a different brand of booster or not, the boosters had "an acceptable safety profile and were immunogenic in adults who had completed a primary Covid-19 vaccine regimen at least 12 weeks earlier," the study team reports.

SOURCE: https://bit.ly/3KN06Xy The New England Journal of Medicine, online January 26, 2022.

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