Effectiveness of COVID-19 vaccines against symptomatic SARS-CoV-2 infection and severe outcomes with variants of concern in Ontario

Nat Microbiol. 2022 Mar;7(3):379-385. doi: 10.1038/s41564-021-01053-0. Epub 2022 Feb 7.

Abstract

SARS-CoV-2 variants of concern (VOC) are more transmissible and may have the potential for increased disease severity and decreased vaccine effectiveness. We estimated the effectiveness of BNT162b2 (Pfizer-BioNTech Comirnaty), mRNA-1273 (Moderna Spikevax) and ChAdOx1 (AstraZeneca Vaxzevria) vaccines against symptomatic SARS-CoV-2 infection and COVID-19 hospitalization or death caused by the Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1) and Delta (B.1.617.2) VOC in Ontario, Canada, using a test-negative design study. We identified 682,071 symptomatic community-dwelling individuals who were tested for SARS-CoV-2, and 15,269 individuals with a COVID-19 hospitalization or death. Effectiveness against symptomatic infection ≥7 d after two doses was 89-92% against Alpha, 87% against Beta, 88% against Gamma, 82-89% against Beta/Gamma and 87-95% against Delta across vaccine products. The corresponding estimates ≥14 d after one dose were lower. Effectiveness estimates against hospitalization or death were similar to or higher than against symptomatic infection. Effectiveness against symptomatic infection was generally lower for older adults (≥60 years) than for younger adults (<60 years) for most of the VOC-vaccine combinations. Our findings suggest that jurisdictions facing vaccine supply constraints may benefit from delaying the second dose in younger individuals to more rapidly achieve greater overall population protection; however, older adults would likely benefit most from minimizing the delay in receiving the second dose to achieve adequate protection against VOC.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 2019-nCoV Vaccine mRNA-1273 / administration & dosage
  • 2019-nCoV Vaccine mRNA-1273 / genetics
  • 2019-nCoV Vaccine mRNA-1273 / immunology*
  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • BNT162 Vaccine / administration & dosage
  • BNT162 Vaccine / genetics
  • BNT162 Vaccine / immunology*
  • COVID-19 / epidemiology
  • COVID-19 / mortality
  • COVID-19 / prevention & control*
  • COVID-19 / virology
  • ChAdOx1 nCoV-19 / administration & dosage
  • ChAdOx1 nCoV-19 / genetics
  • ChAdOx1 nCoV-19 / immunology*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Ontario / epidemiology
  • SARS-CoV-2 / classification
  • SARS-CoV-2 / genetics
  • SARS-CoV-2 / immunology*
  • Young Adult

Substances

  • ChAdOx1 nCoV-19
  • 2019-nCoV Vaccine mRNA-1273
  • BNT162 Vaccine

Supplementary concepts

  • SARS-CoV-2 variants