BACKGROUND AND PURPOSE:

• Tenforde et al. (CDC MMWR, 2022) assessed the effectiveness of the updated bivalent mRNA COVID-19 vaccine boosters (containing mRNA targeting Omicron lineages of SARS-CoV-2) at preventing COVID-19 medical encounters

METHODS:

• Cohort study
  • Multistate VISION Network (See ‘Learn More – Primary Sources’ below)
• Population
  • Immunocompetent adults aged ≥18 years
  • Emergency department/urgent care (ED/UC) encounter or hospitalization for a COVID-19–like illness
• Exposure
  • Unvaccinated: No vaccination
  • Monovalent only: Vaccinated with 2, 3 or 4 doses of a monovalent-only mRNA vaccine
  • Mono + Bivalent: Vaccinated with 2, 3, or 4 monovalent doses plus a bivalent booster dose ≥60 days after receipt of their last monovalent dose
• Study design
  • Multivariable logistic regression was used to calculate odds ratios, with adjustment for age, race and ethnicity, sex, calendar day, geographic region and SARS-CoV-2 circulation
• Primary outcome
  • Vaccine effectiveness (VE) against ED/UC encounters and hospitalizations

RESULTS:

• ED/UC patients COVID-19 positive: 9009 | ED/UC patients COVID-19 negative: 69,294
  • Unvaccinated: 31%
  • Mono + Bivalent: 5%
• VE of a bivalent booster dose (after 2, 3, or 4 monovalent doses) against ED/UC encounters was
  • Compared to no vaccination: 56%
  • Compared to monovalent only vaccination with last dose 2 to 4 months earlier: 31%
  • Compared to monovalent only vaccination with last dose ≥11 months earlier: 50%
• VE of a bivalent booster dose (after 2, 3, or 4 monovalent doses) against hospitalizations was
  • Compared to no vaccination: 57%
  • Compared to monovalent only vaccination with last dose 5 to 7 months earlier: 38%
  • Compared to monovalent only vaccination with last dose ≥11 months earlier: 45%

CONCLUSION:

• During September to November 2022, when the BA.5 and other Omicron sublineages were predominant, bivalent COVID-19 vaccine was effective at preventing patients from requiring medical care for COVID-19 infection compared to monovalent vaccine or no vaccine
• The authors state

These findings support efforts to improve coverage with bivalent vaccines, although optimal timing for receipt of bivalent vaccine booster doses needs to be established 

Learn More – Primary Sources:

Early Estimates of Bivalent mRNA Vaccine Effectiveness in Preventing COVID-19–Associated Emergency Department or Urgent Care Encounters and Hospitalizations Among Immunocompetent Adults