BACKGROUND AND PURPOSE:

• Both mRNA COVID-19 vaccines (Moderna and Pfizer/BioNTech) have been shown to be effective at preventing symptomatic COVID-19 in phase III trials
• Thompson et al. (CDC MMWR, 2021) quantified SARS-CoV-2 infections among vaccinated, partially-vaccinated, and non-vaccinated essential personnel every week for 12 weeks

METHODS:

• Prospective cohort study (December 14, 2020 to March 13, 2021)
• Setting
  • Eight locations in the US
• Participants
  • Health care personnel | First responders | Other essential and frontline workers
  • No previous laboratory documentation of SARS-CoV-2 infection
• Exposure
  • Vaccination status
    • Fully immunized (≥14 days after second dose)
    • Partially immunized (≥14 days after first dose and before second dose)
    • Unvaccinated
• Study design
  • The CDC tested for SARS-CoV-2 infections
    • Every week regardless of symptom status and
    • At the onset of symptoms consistent with COVID-19–associated illness
  • SARS-CoV-2 infections were confirmed by RT-PCR
• Statistical analysis
  • Authors accounted for time-varying vaccination status
  • Results adjusted for site

RESULTS:

• 3,950 participants with no previous SARS-CoV-2 infection
  • Fully immunized: 62.8%
  • Partially immunized: 12.1%
• SARS-CoV-2 infection
  • Unvaccinated: 1.38 infections per 1,000 person-days
  • Fully immunized: 0.04 infections per 1,000 person-days
  • Partially immunized: 0.19 infections per 1,000 person-days
• Estimated mRNA vaccine effectiveness for prevention of infection
  • Full immunization: 90%
  • Partial immunization: 80%

CONCLUSION:

• Both mRNA COVID-19 vaccines are effective at preventing infection, both symptomatic and asymptomatic, in essential personnel in real world conditions
• The authors conclude

These interim vaccine effectiveness findings for both Pfizer-BioNTech’s and Moderna’s mRNA vaccines in real-world conditions complement and expand upon the vaccine effectiveness estimates from other recent studies and demonstrate that current vaccination efforts are resulting in substantial preventive benefits among working-age adults

They reinforce CDC’s recommendation of full 2-dose immunization with mRNA vaccines

COVID-19 vaccination is recommended for all eligible persons 

Learn More – Primary Sources:

Interim Estimates of Vaccine Effectiveness of BNT162b2 and mRNA-1273 COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Health Care Personnel, First Responders, and Other Essential and Frontline Workers — Eight U.S. Locations, December 2020–March 2021