BACKGROUND AND PURPOSE:

• Pilishvili et al. (NEJM, 2021) evaluated COVID-19 vaccine effectiveness in health care personnel according to vaccine product

METHODS:

• Test-negative case-control study
• Participants
  • Health care personnel across 25 states who had been tested for SARS-CoV-2
  • Enrolled from December 2020 (2 weeks following introduction of COVID-19 vaccine) through May 2021
• Exposures
  • Vaccine product
    • Moderna
    • Pfizer
  • Vaccine status
    • Partial vaccination
      • 14 days after receipt of the first dose through 6 days after receipt of the second dose
    • Complete vaccination
      • ≥7 days after receipt of the second dose
• Study design
  • Cases and controls were matched according to week of the test date and site
    • Cases were determined by PCR or antigen-based tests and at least one COVID-19 symptom
  • Vaccine effectiveness was adjusted for age, race and ethnic group, underlying conditions, and exposures to persons with COVID-19
• Primary outcome
  • Vaccine effectiveness

RESULTS:

• Cases: 1482 participants | Controls: 3449 participants
• Vaccine effectiveness for partial vaccination
  • Pfizer: 77.6% (95% CI, 70.9 to 82.7)
  • Moderna: 88.9% (95% CI, 78.7 to 94.2)
• Vaccine effectiveness for complete vaccination
  • Pfizer: 88.8% (95% CI, 84.6 to 91.8)
  • Moderna: 96.3% (95% CI, 91.3 to 98.4)
• Vaccine effectiveness was similar in subgroups defined according to a
  • Age (<50 years or ≥50 years)
  • Race and ethnic group
  • Presence of underlying conditions
  • Level of patient contact
• Evidence of waning vaccine effect assessed in 2 week intervals after receipt of second dose
  • Lower during weeks 9 through 14 than during weeks 3 through 8 after receipt of the second dose, but large overlapping CIs

CONCLUSION:

• During the study period, vaccine effectiveness in health care personnel for both the Pfizer and Moderna COVID-19 vaccines was high (~89% for Pfizer and ~96% for Moderna)
• Vaccine effectiveness was similarly high for adults of different ages, races/ethnicities, and with underlying conditions
• The authors state

In this population of health care personnel, vaccine effectiveness was similar among persons with underlying medical conditions or other risk factors for severe Covid-19, including pregnancy; in different subgroups of health care personnel defined according to job category; and in racial and ethnic groups that have been disproportionately affected by the pandemic

The long-term duration of protection and the effectiveness of these vaccines against emerging variants is unknown and should be monitored to indicate whether changes to vaccine composition or vaccine policy are needed

Learn More – Primary Sources:

Effectiveness of mRNA Covid-19 Vaccine among U.S. Health Care Personnel

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