Effectiveness of MRNA booster vaccine among healthcare workers in New York City during the Omicron surge, December 2021 to January 2022

Elizabeth V. Robilotti, Karissa Whiting, Anabella Lucca, Chester Poon, Krupa Jani, Tracy McMillen, Scott Freeswick, Deborah Korenstein, N. Esther Babady, Venkatraman E. Seshan, Mini Kamboj

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Objective: 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 to January 15, 2022, SARS-CoV-2 infections among HCWs at a large tertiary cancer centre in New York City were examined to estimate infection rates (aggregated positive tests / person-days) and 95% CIs over the Omicron period in 3D and 2D mRNA vaccinated HCWs and were compared using rate ratios. We described the clinical features of post-vaccine infections and impact of prior (pre-Omicron) COVID infection on vaccine effectiveness. Results: Among the 20857 HCWs in our cohort, 20,660 completed the 2D series with an mRNA vaccine during our study period and 12461 had received a third dose by January 15, 2022. The infection rate ratio for 3D versus 2D vaccinated HCWs was 0.667 (95% CI 0.623, 0.713) for an estimated 3D vaccine effectiveness of 33.3% compared to two doses only during the Omicron dominant period from December 15, 2021 to January 15, 2022. Breakthrough Omicron infections after 3D + 14 days occurred in 1,315 HCWs. Omicron infections were mild, with 16% of 3D and 11% 2D HCWs being asymptomatic. Discussion: Study demonstrates improved vaccine-derived protection against COVID-19 infection in 3D versus 2D mRNA vaccinees during the Omicron surge. The advantage of 3D vaccination was maintained irrespective of prior COVID-19 infection status.

Original languageEnglish
Pages (from-to)1624-1628
Number of pages5
JournalClinical Microbiology and Infection
Volume28
Issue number12
DOIs
StatePublished - Dec 2022
Externally publishedYes

Keywords

  • Booster breakthrough infections
  • SARS-CoV-2
  • Vaccine effectiveness

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