COVID-19 vaccine antibody responses in community-dwelling adults to 48 weeks post primary vaccine series

We report a decentralized prospective cohort study of self-reported adverse events and antibody responses to COVID vaccines derived from dried blood spots. Data are presented for 911 older (aged >70 years) and 375 younger (30-50 years) recruits to 48 weeks after the primary vaccine series. After a single vaccine, 83% younger and 45% older participants had overall seropositivity (p < 0.0001) increasing to 100/98% with the second dose, respectively (p = 0.084). A cancer diagnosis (p = 0.009), no mRNA-1273 vaccine doses (p <0 . 0001), and older age (p <0 .0001) predicted lower responses. Antibody levels declined in both cohorts at 12 and 24 weeks increasing with booster doses. At 48 weeks, for participants with 3 vaccine doses, the median antibody levels were higher in the older cohort (p = 0.04) with any dose of mRNA-1273 (p <0 . 0001) and with COVID infection (p <0 .001). The vaccines were well tolerated. Breakthrough COVID infections were uncommon (16% older cohort, 29% younger cohort; p < 0.0001) and mild.

Automated summary

This study is a decentralized prospective cohort study that examines adverse events and antibody responses to COVID vaccines using dried blood spots. The study includes 911 older participants and 375 younger participants followed for 48 weeks. The results show that both age and the type of vaccine received influenced antibody responses, with higher levels seen in the older cohort and those who received mRNA-1273 vaccine.