Durability of mRNA-1273 against COVID-19 in the time of Delta: Interim results from an observational cohort study

PLoS One. 2022 Apr 28;17(4):e0267824. doi: 10.1371/journal.pone.0267824. eCollection 2022.

Abstract

Background: We conducted a prospective cohort study at Kaiser Permanente Southern California to study the vaccine effectiveness (VE) of mRNA-1273 over time and during the emergence of the Delta variant.

Methods: The cohort for this planned interim analysis consisted of individuals aged ≥18 years receiving 2 doses of mRNA-1273 through June 2021, matched 1:1 to randomly selected unvaccinated individuals by age, sex, and race/ethnicity, with follow-up through September 2021. Outcomes were SARS-CoV-2 infection, and COVID-19 hospitalization and hospital death. Cox proportional hazards models were used to estimate adjusted hazard ratios (aHR) with 95% confidence intervals (CIs) comparing outcomes in the vaccinated and unvaccinated groups. Adjusted VE (%) was calculated as (1-aHR)x100. HRs and VEs were also estimated for SARS-CoV-2 infection by age, sex, race/ethnicity, and during the Delta period (June-September 2021). VE against SARS-CoV-2 infection and COVID-19 hospitalization was estimated at 0-<2, 2-<4, 4-<6, and 6-<8 months post-vaccination.

Results: 927,004 recipients of 2 doses of mRNA-1273 were matched to 927,004 unvaccinated individuals. VE (95% CI) was 82.8% (82.2-83.3%) against SARS-CoV-2 infection, 96.1% (95.5-96.6%) against COVID-19 hospitalization, and 97.2% (94.8-98.4%) against COVID-19 hospital death. VE against SARS-CoV-2 infection was similar by age, sex, and race/ethnicity, and was 86.5% (84.8-88.0%) during the Delta period. VE against SARS-CoV-2 infection decreased from 88.0% at 0-<2 months to 75.5% at 6-<8 months.

Conclusions: These interim results provide continued evidence for protection of 2 doses of mRNA-1273 against SARS-CoV-2 infection over 8 months post-vaccination and during the Delta period, and against COVID-19 hospitalization and hospital death.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 2019-nCoV Vaccine mRNA-1273
  • Adolescent
  • Adult
  • COVID-19* / epidemiology
  • COVID-19* / prevention & control
  • Cohort Studies
  • Humans
  • Prospective Studies
  • SARS-CoV-2 / genetics

Substances

  • 2019-nCoV Vaccine mRNA-1273

Supplementary concepts

  • SARS-CoV-2 variants

Grants and funding

This work and the medical writing and editorial assistance provided by MEDiSTRAVA were funded by Moderna, Inc.