COVID-19 Vaccine Prevents Against Reinfection

WEDNESDAY, Dec. 7, 2022 (HealthDay News) — Completing a primary COVID-19 vaccination series is associated with significant protection against reinfection among previously infected individuals, according to a study published online Nov. 22 in PLOS Medicine.

Katrine Finderup Nielsen, from the Statens Serum Institut in Copenhagen, Denmark, and colleagues evaluated the vaccine effectiveness against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection, COVID-19-related hospitalization, and COVID-19-related death in individuals with prior SARS-CoV-2 infection. The reinfection analysis included 44,192 SARS-CoV-2 infections.

The researchers found that 19.2 percent of individuals had completed their primary vaccination series during the alpha period, 64.6 percent during the delta period, and 64.6 percent during the omicron period. Vaccine effectiveness peaked at 71 percent at ≥104 days after vaccination during the alpha period, 94 percent 14 to 43 days after vaccination during the delta period, and 60 percent 14 to 43 days after vaccination during the omicron period. During the omicron period, waning immunity following vaccination was most pronounced.

“Even though vaccination seems to protect to a lesser degree against reinfection with the omicron variant, these findings are of public health relevance as they show that previously infected individuals still benefit from COVID-19 vaccination in all three variant periods,” the authors write.