Individuals who are not vaccinated against COVID-19 are more than twice as likely to have a COVID-19 reinfection compared with fully vaccinated individuals, according to a Centers for Disease Control and Prevention study.
"These findings suggest that among persons with previous SARS-CoV-2 infection, full vaccination provides additional protection against reinfection," the authors wrote. "All eligible persons should be offered vaccination, including those with previous SARS-CoV-2 infection, to reduce their risk for future infection."
The findings, published on August 6 in the CDC's Morbidity and Mortality Weekly Report (MMWR), detail a case-control evaluation of the association between vaccination and SARS-CoV-2 reinfection in Kentucky during May–June 2021 among persons previously infected with SARS-CoV-2 in 2020. The comparison included 246 case-patients who were reinfected and 492 controls who were infected in 2020 but not in May-June 2021.
Kentucky residents aged ≥18 years with SARS-CoV-2 infection confirmed by positive nucleic acid amplification test or antigen test results† reported in Kentucky’s National Electronic Disease Surveillance System (NEDSS) during March–December 2020 were eligible for inclusion. Case-patients were considered fully vaccinated if a single dose of Janssen (Johnson & Johnson) or a second dose of an mRNA vaccine (Pfizer-BioNTech or Moderna) was received at least 14 days before the reinfection date.
Among case-patients, 20.3% were fully vaccinated, compared with 34.3% of controls. Kentucky residents with previous infections who were unvaccinated had 2.34 times the odds of reinfection compared with those who were fully vaccinated. Partial vaccination was not significantly associated with reinfection risk, but this group was small (6.9% of case-patients and 7.9% of controls), which limited statistical power.