Vaccine-induced immune response to Omicron diminishes considerably over time

According to new clinical trial data, although COVID-19 booster vaccinations in adults produce increasing levels of antibodies against the Omicron variant of SARS-CoV-2, the levels of antibodies decrease considerably within three months. The findings, published recently in Cell Reports Medicine, are from a study sponsored by a part f the National Institution of Health, the National Institute of Allergy and Infectious Diseases. The trial was run by NIAID’s Infectious Diseases Clinical Research Consortium.

Investigators had COVID-19 booster vaccines administered to adults in the US who, under Emergency Use Authorization, had formerly received a primary COVID-19 vaccination series. Several participants received the same vaccine as their initial series, and others received a different vaccine. Immune responses were then evaluated over time by investigators. Results formerly stated in The New England Journal of Medicine showed all combinations of primary and booster vaccines lead to higher neutralizing antibody levels in the recipients.

In the new analysis, it has been reported that nearly all vaccine combinations evaluated had produced higher levels of neutralizing antibodies to the Omicron BA.1 sub-lineage. Although, in the group that received Ad26.COV2.S as a primary vaccine and boost, antibody levels against Omicron were low. In addition, immune responses to Omicron in all groups diminished considerably, with levels of neutralizing antibodies decreasing from 2.4- to 5.3 three months after the booster vaccine was administered. Omicron sub-lineages BA.4/BA.5 and BA.2.12.1 were 1.5 and 2.5 times less prone to neutralization, respectively, compared to the BA.1 sub-lineage, and 7.5 and 12.4 times less inclined relative to the ancestral D614G strain. The dominant variant in the US currently being BA.5.

The findings are consistent with real-world reports showing weakening protection against SARS-CoV-2 infection during the Omicron wave in people who received an initial vaccine series plus a booster shot, the authors note. In addition, the immune response to Omicron sub-lineages show reduced susceptibility to these quickly developing subvariants. The data can be used to notify decisions regarding upcoming vaccine schedule recommendations, including the necessity for variant vaccine boosting.