LAUSR

We aimed to perform meta‐analyses to summarize the overall effectiveness of the mRNA‐1273 vaccine against COVID‐19 caused by the Delta variant from real‐world studies. A systematic literature search with no language restriction was performed in electronic databases to identify eligible observational studies that reported the effectiveness of the mRNA‐1273 vaccine to prevent reverse transcription‐polymerase chain reaction (RT‐PCR) confirmed COVID‐19 caused by Delta variant of SARS‐CoV‐2 (B.1.617.2). A random‐effects meta‐analysis model was used to estimate the pooled odds ratio (OR) at a 95% confidence interval (CI), and the vaccine effectiveness was indicated as (pooled OR − 1)/OR. Five studies were included for this systematic review and meta‐analysis. The meta‐analysis revealed that the administration of mRNA‐1273 vaccine protected against RT‐PCR confirmed COVID‐19 caused by Delta variant ≥21 days post first dose, with pooled vaccine effectiveness of 66% (95% CI: 65%–67%), as well as ≥14 days after the second dose, with pooled vaccine effectiveness of 91% (95% CI: 84%–95%). In conclusion, the mRNA‐1273 vaccine offers a substantial protection rate against RT‐PCR confirmed COVID‐19 caused by the Delta variant upon full vaccination, although with slightly reduced effectiveness relative to other strains of SARS‐CoV‐2.