Data from 10 U.S. states show waning of mRNA SARS-CoV-2 vaccine effectiveness against moderate and severe COVID-19, researchers report, supporting “recommendations for a booster dose after a primary series and consideration of additional booster doses.”
The VISION network of 261 hospitals, 272 emergency departments, and 119 urgent care centers contributed testing and outcomes information that was analyzed using a test-negative case-control study design. “45,903 people admitted to hospital with covid-19 (cases) were compared with 213,103 people with covid-like illness who tested negative for SARS-CoV-2 (controls), and 103,287 people admitted to emergency department or urgent care with covid-19 (cases) were compared with 531,168 people with covid-like illness who tested negative for SARS-CoV-2,” the authors report. “In the omicron period, vaccine effectiveness against covid-19 requiring admission to hospital was 89% (95% confidence interval 88% to 90%) within two months after dose 3 but waned to 66% (63% to 68%) by four to five months. Vaccine effectiveness of three doses against emergency department or urgent care visits was 83% (82% to 84%) initially but waned to 46% (44% to 49%) by four to five months. Waning was evident in all subgroups, including young adults and individuals who were not immunocompromised; although waning was more in people who were immunocompromised. Vaccine effectiveness increased among most groups after a fourth dose in whom this booster was recommended.”