Effectiveness of mRNA booster vaccine among health Care workers in New York City during the omicron surge, December 2021- January 2022.
Academic Article
Overview
abstract
OBJECTIVES: To describe effectiveness of mRNA vaccines by comparing 2-dose (2D) and 3-dose (3D) healthcare worker (HCW) recipients in the setting of Omicron variant dominance. Performance of 2D and 3D vaccine series against SARS-CoV-2 variants and the clinical outcomes of HCWs may inform return-to-work guidance. METHODS: In a retrospective study from December 15, 2020 - January 15, 2022, SARS CoV-2 infections among HCWs at a large tertiary cancer center in New York City (NYC) were examined to estimate infection rates over the omicron period (aggregated positive tests/person-days) and 95% CIs in 2D and 3D mRNA vaccinated HCWs and were compared using rate ratios. We describe the clinical features of post-vaccine infections and impact of prior (pre-Omicron) COVID infection on vaccine effectiveness (VE). RESULTS: Among the 20,857 HCWs in our cohort, 20,660 completed the 2D series with an mRNA vaccine during our study period and 12,461 had received a third dose by January 15, 2022. The infection rate ratio for 2D vs. 3D vaccinated HCWs was 0.667 (95% CI 0.623, 0.713) for an estimated 3D VE of 33.2% compared to 2 doses only during the Omicron dominant period from 12/15/21- 1/15/22. Breakthrough (BT) Omicron infections after 3D + 14 days occurred in 1315 HCWs. Omicron infections were mild, with 16% of 3D and 11% 2D HCWs being asymptomatic. CONCLUSIONS: Study demonstrates improved vaccine-derived protection against COVID-19 infection in 3D vs. 2D mRNA vaccinees during the Omicron surge. The advantage of 3D vaccination was maintained irrespective of prior COVID-19 infection status.
