Fewer reinfections among older participants
Researchers from Clalit Health Services in Tel Aviv, Israel, retrospectively analyzed the electronic health records of 83,356 recipients of at least one dose of the Pfizer/BioNTech COVID-19 vaccine after recovery from infection and 65,676 unvaccinated survivors.
The observational study began on Mar 1, 2021, after the Israeli Ministry of Health approved COVID-19 vaccination for all patients who had recovered from COVID-19 3 or more months before. All participants had recovered from a primary SARS-CoV-2 infection from Aug 23, 2020 (190 days before the study period), to May 31, 2021 (90 days after study initiation). Average patient age was 39.3 years (range, 16 to 110).
COVID-19 reinfection occurred in 354 of 83,356 vaccinated participants (0.4%; 2.5 cases per 100,000 person-days) and in 2,168 of 65,676 of their unvaccinated peers (3.3%; 10.2 per 100,000).
In the 16- to 64-year age-group, 326 of 73,972 vaccinated participants (0.4%; 2.6 cases per 100,000 person-days) were reinfected, compared with 2,120 of 60,877 of their unvaccinated counterparts (3.5%; 10.8 per 100,000).
Among patients 65 years and older, reinfection occurred in 28 of 9,384 vaccinated (0.3%; 1.5 cases per 100,000 person-days) and 48 of 4,799 unvaccinated participants (1.0%; 3.0 per 100,000). The study authors said that the difference between the two age-groups may be explained by an assumption that older COVID-19 survivors would have taken more precautions against reinfection than younger people.
Source: COVID vaccines offer lasting protection against reinfection, studies find | CIDRAP