Two reports yesterday in the New England Journal of Medicine detail the effects of the COVID-19 vaccine booster on Omicron (B.1.1.529) variant antibody levels, one finding that concentrations were 20 times higher after a third Moderna vaccine dose than after the primary series, and the other showing the benefits of longer intervals between doses.20-fold jump in Omicron antibodies after boosterIn the first study, a team led by Moderna scientists assessed neutralizing antibody responses to a third Moderna vaccine dose against the Omicron variant versus the wild-type (D614G), Beta (B1351), and Delta (B1617.2) strains.
The study built upon a pilot study that found that vaccine immune response to Omicron was lower than that to the wild-type and Beta strains.The researchers measured Omicron variant neutralization using serum samples from participants who had received the two-dose Moderna vaccine regimen in the Coronavirus Efficacy (COVE) phase 2 and 3 trials of that vaccine.Participants were randomly assigned to receive either a third dose of the prototypical Moderna vaccine (the version available under an emergency use authorization for US adults), a 1:1 mix of the authorized vaccine and Beta variant messenger RNAs (mRNAs), or a 1:1 mix of Beta and Delta mRNAs.The Moderna vaccine induced detectable antibodies against Omicron in 85% of participants 1 month after the second dose.
The 50% inhibitory dilution (ID50) geometric mean titer was 35.0 times lower against Omicron than against the wild-type strain.
Independently performed live-virus focus-reduction and pseudovirus neutralization tests yielded similar results.Seven months after primary vaccine series completion, anti-Omicron antibodies were found in only 55% of