Vaccine Effectiveness Against SARS-CoV-2 Infection Wanes Over Time

TUESDAY, June 14, 2022 (HealthDay News) — Vaccine effectiveness (VE) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and symptomatic COVID-19 wanes over time, but remains strong against severe COVID-19, according to a review published online May 7 in BMC Infectious Diseases.

Paddy Ssentongo, M.D., Ph.D., from the Penn State College of Medicine and Milton S. Hershey Medical Center, and colleagues conducted a systematic review and meta-analysis of the duration of VE against SARS-CoV-2 infection, symptomatic COVID-19, and severe COVID-19. Data were included from 18 studies representing nearly 7 million individuals.

The researchers found that VE against all SARS-CoV-2 infections decreased from 83 percent in the first month after completion of the original vaccination series to 22 percent at five months or longer. In addition, a decline was seen in VE against symptomatic COVID-19, from 94 percent in the first month after vaccination to 64 percent by the fourth month. For all ages, VE against severe COVID-19 was high overall, with VE of 90 percent at five months or longer after full vaccination. In individuals aged ≥65 years and those who received Ad26.COV2.S, VE against severe COVID-19 was lower.

“COVID-19 vaccines are critical for ending the pandemic, and even if their effectiveness against infection wanes, they provide key and important protection against severe COVID-19 disease that can lead to hospitalization,” Ssentongo said in a statement. “Future studies will need to explore the evolution of effectiveness against omicron and newer variant-related hospitalizations.”

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