Covid-19 Vaccine Booster Increases Antibody Response in Macaques

Researchers report that a booster dose of the Moderna Covid-19 vaccine given to rhesus macaques enhanced their immune response, providing protection against all known circulating SARS-CoV-2 variants.

Several variants of concern show reduced sensitivity to vaccine-elicited immunity. And, vaccine-induced antibody responses wane over time. Both factors contribute to the continuing pandemic. 

A team led by scientists at NIAID’s Vaccine Research Center set out to test whether a booster dose could improve antibody responses, especially against variants of concern, including Delta. The study results appeared in Science.

Researchers gave the primary two-dose regimen of the Moderna Covid-19 vaccine to the macaques. Six months later, they received a booster dose of the same vaccine, which increased levels of neutralizing antibodies.

Nine weeks after the boost, the monkeys were exposed to the SARS-CoV-2 Beta variant. Viral load was negligible in their lungs and substantially reduced in their noses compared to unvaccinated monkeys. These data suggest that a booster triggers a strong immune memory response and longer-lasting immunity. 

The researchers focused on the Beta variant because it has consistently proven highly resistant to neutralization. While the Delta variant is highly transmissible, it has only an intermediate ability to resist neutralization.

The results suggest that an mRNA booster vaccine in people could improve the duration and potency of protection against upper and lower airway infection by any of the circulating variants, thus protecting against severe disease and potentially limiting mild infection and virus transmission. Boosters may be especially beneficial for high-risk groups including the elderly, people with pre-existing conditions and those who responded poorly to primary vaccination.