Completing a primary COVID-19 vaccination series is associated with significant protection against reinfection among previously infected individuals, according to a study published in PLOS Medicine. Palle Valentiner-Branth, MD, PhD, and colleagues evaluated the vaccine effectiveness against 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% of individuals had completed their primary vaccination series during the alpha period, 64.6% during the delta period, and 64.6% during the omicron period. Vaccine effectiveness peaked at 71% at 104 or more days after vaccination during the alpha period, 94% at 14-43 days after vaccination during the delta period, and 60% at 14-43 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,” Dr. Valentiner-Branth and colleagues wrote.