Mix-n-match COVID boosters may produce more durable immunity

A single-center study today in JAMA Network Open finds longer-lasting humoral and cellular immune responses in US adults given a Johnson & Johnson (J&J) COVID-19 vaccine booster rather than a Pfizer/BioNTech booster after receiving two doses of the Pfizer vaccine at least 6 months earlier.

Researchers from Beth Israel Deaconess Medical Center led the study of 68 adults in Boston given either a Pfizer or a J&J COVID-19 booster 6 or more months after receiving two doses of the Pfizer vaccine. Enrollment took place from Aug 12 to Oct 25, 2021, and follow-up lasted 4 months.

The median age of the 41 recipients of a J&J booster was 36 years, while it was 35 in the 27 Pfizer recipients. Of all participants, 82% were women, 78% were White, 10% were Asian, 6% were Black, 6% were Hispanic or Latino, and 4% were more than one race.

Antibodies fell dramatically 4 months after Pfizer booster

Both boosters were tied to improved humoral and cellular immune responses, including against SARS-CoV-2 variants of concern such as Omicron. A Pfizer booster was tied to a rapid rise in Omicron-neutralizing antibodies that peaked at a median titer of 1,018 in week 2, and then dropped 6.9-fold to 148 at 4 months. In contrast, after a J&J booster, Omicron-neutralizing antibodies rose, peaking at a median titer of 859 in week 4, and then fell only 2.1-fold to 403 by 4 months.

The findings, the researchers said, show that both COVID-19 vaccine strategies (same or different booster) increase Omicron-neutralizing antibody and T-cell responses in Pfizer vaccine recipients but that responses at 4 months were higher after the J&J booster than after the Pfizer version.

"A heterologous mix-and-match vaccine strategy was associated with durable antibody and T-cell responses against the SARS-CoV-2 Omicron variant," they wrote. "These data suggest potential immunologic benefits of mix-and-match heterologous COVID-19 vaccine regimens and emphasizes the importance of durability for COVID-19 vaccine boosting strategies."

The authors noted that previously reported rapid waning of SARS-CoV-2 antibody responses and clinical effectiveness after third and fourth doses of the Pfizer COVID-19 vaccine has led to recommendations for frequent mRNA vaccine boosting, "which may be challenging to sustain as a long-term policy in the developed world and difficult to implement in the developing world," they wrote. "Future studies could explore reduced booster doses as well as Omicron-containing boosters."

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