BACKGROUND AND PURPOSE:

• Using real-world data, Cavanaugh et al. (CDC MMWR, 2021) assessed the association between vaccination and SARS-CoV-2 reinfection among persons previously infected with SARS-CoV-2

METHODS:

• Case-control study
  • Residents of Kentucky
• Participants
  • ≥18 years
  • Confirmed SARS-CoV-2 infection between March and December of 2020
• Exposures
  • Reinfection status
    • Case patients: SARS-CoV-2 infection in 2020 and another positive test between May and June 2021
    • Control patients: SARS-CoV-2 infection in 2020 and no reinfection
  • Vaccination status
    • Fully vaccinated: first dose of J&J or second dose of Pfizer/Moderna was received ≥14 days before the reinfection date
    • Partially vaccinated: ≥1 dose of vaccine, but either the vaccination series was not completed or the final dose was received <14 days before the case-patient’s reinfection date
    • No vaccination
• Matching of cases and controls
  • Based on age, sex, and date of initial infection

RESULTS:

• Case-patients: 246 | Control patients: 492
  • 60.6% female, 82.9% of case patients initially infected October to December 2020
  • Case-patients full vaccinated: 20.3%
  • Control-patients fully vaccinated: 34.3%
• Partial vaccination
  • Case-patients: 6.9%
  • Controls: 7.9%
• Compared to patients with previous infections who were fully vaccinated, those with previous infections who were unvaccinated were 2.34 times more likely to experience reinfection
  • OR 2.34 (95% CI, 1.58 to 3.47)
• Partial vaccination was not significantly associated with reinfection
  • OR 1.56 (95% CI, 0.81 to 3.01)

CONCLUSION:

• In the real world, individuals with a history of SARS-CoV-2 infection that were unvaccinated were 2.34 times more likely to experience reinfection that those who were vaccinated
• Lack of a significant association with partial vs full vaccination should be interpreted with caution | Statistical power limited due to small ‘n’ of individuals who were partially vaccinated
• To reduce the risk of reinfection, everyone that is eligible for a COVID-19 vaccine should be offered one, even if they have previously been infected
• The authors state

The findings from this study suggest that among previously infected persons, full vaccination is associated with reduced likelihood of reinfection, and, conversely, being unvaccinated is associated with higher likelihood of being reinfected

Learn More – Primary Sources:

Reduced Risk of Reinfection with SARS-CoV-2 After COVID-19 Vaccination – Kentucky, May-June 2021

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