Vaccine-Induced Immunity to Omicron Wanes Over Time

New clinical trial data reveals that while Covid-19 booster vaccinations in adults elicit high levels of neutralizing antibodies against the Omicron variant of SARS-CoV-2, antibody levels decrease substantially within 3 months. The findings, published in Cell Reports Medicine, are from a study led by NIAID’s Infectious Diseases Clinical Research Consortium. 

As part of a “mix and match” clinical trial, investigators administered Covid-19 booster shots to adults in the U.S. who had previously received a primary Covid-19 vaccination series. Some participants received the same vaccine as their primary series; others received a different vaccine. Investigators then evaluated immune responses over time. 

In the new analysis, investigators found nearly all vaccine combinations evaluated elicited high levels of neutralizing antibodies to the Omicron BA.1 sub-lineage. Immune responses to Omicron in all groups waned substantially, with neutralizing antibody levels decreasing 2.4- to 5.3-fold by 3 months post-boost. 

Omicron sub-lineages BA.2.12.1 and BA.4/BA.5 were 1.5 and 2.5 times less susceptible to neutralization, respectively, compared to the BA.1 sub-lineage, and 7.5 and 12.4 times less susceptible relative to the ancestral D614G strain. BA.5 currently is the dominant variant in the U.S. 

Additionally, the immune response to Omicron sub-lineages show reduced susceptibility to these rapidly emerging subvariants. The data could be used to inform decisions regarding future vaccine schedule recommendations, including the need for variant vaccine boosting.