Background: The CDC recently defined being "up-to-date" on COVID-19 vaccination as having received at least one dose of a COVID-19 bivalent vaccine. The purpose of this study was to compare the risk of COVID-19 among those "up-to-date" and "not up-to-date".
Methods: Employees of Cleveland Clinic in Ohio, USA, in employment when the COVID-19 bivalent vaccine first became available, and still employed when the XBB lineages became dominant, were included. Cumulative incidence of COVID-19 since the XBB lineages became dominant was compared across the"up-to-date" and "not up-to-date" states, by treating COVID-19 bivalent vaccination as a time-dependent covariate whose value changed on receipt of the vaccine. Risk of COVID-19 by vaccination status was also evaluated using multivariable Cox proportional hazards regression adjusting for propensity to get tested for COVID-19, age, sex, most recent prior SARS-CoV-2 infection, and number of prior vaccine doses.
Results: COVID-19 occurred in 1475 (3%) of 48 344 employees during the 100-day study period. The cumulative incidence of COVID-19 was lower in the "not up-to-date" than the "up-to-date" state. On multivariable analysis, being "up-to-date" was not associated with lower risk of COVID-19 (HR, 1.05; 95% C.I., 0.88-1.25; P-value, 0.58). Results were very similar when those 65 years and older were only considered "up-to-date" after 2 doses of the bivalent vaccine.
Conclusions: Since the XBB lineages became dominant, adults "up-to-date" on COVID-19 vaccination by the CDC definition do not have a lower risk of COVID-19 than those "not up-to-date", bringing into question the value of this risk classification definition.
Copyright: © 2023 Shrestha et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.