LAUSR

Key Points Question How does the effectiveness of COVID-19 vaccines against laboratory-confirmed Omicron infection and symptomatic disease change at different times from last dose administration and number of doses, and how does this compare with previously circulating SARS-CoV-2 variants and subvariants? Findings This systematic review and meta-analysis of secondary data from 40 studies found that the estimated vaccine effectiveness against both laboratory-confirmed Omicron infection and symptomatic disease was lower than 20% at 6 months from the administration of the primary vaccination cycle and less than 30% at 9 months from the administration of a booster dose. Compared with the Delta variant, a more prominent and quicker waning of protection was found. Meaning These findings suggest that the effectiveness of COVID-19 vaccines against Omicron rapidly wanes over time.