According to a new study by the US Centers of Disease Control and Prevention (CDC), the efficacy of a third dose of the Pfizer and Moderna COVID-19 vaccines declines considerably by the fourth month following administration.

The results of the study are based on over 241,204 visits to the emergency department or an urgent care clinic, and 93,408 hospital admissions, which were more serious, among adults with COVID-like illness, between August 26, last year and January 22, this year.

Investigators determined vaccine efficacy by comparing the likelihood of a positive COVID-19 test between vaccinated and unvaccinated patients. During the period when Omicron variant was predominant, vaccine efficacy against COVID-related emergency department or urgent care visits was 87% in the two months after a third jab, while it declined to 66% by the fourth month. Efficacy against hospitalization was 91% in the first two months, and dropped to 78% by the fourth month after the third shot… (NDTV – AFP, February 12, 2022)