HealthDay News — With increasing prevalence of the delta variant of SARS-CoV-2, there was a decline in vaccine protection against SARS-CoV-2 infection, while protection remained stronger against hospitalization and death, according to research published in the September 10 early-release issue of the US Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Heather M. Scobie, PhD, from the CDC COVID-19 Response Team, and colleagues analyzed reported COVID-19 cases, hospitalizations, and deaths among persons aged 18 years and older during April 4 to July 17, 2021, by vaccination status across 13 US jurisdictions using linked case surveillance and immunization registry data.

The researchers found that the age-standardized incidence rate ratios (IRRs) for cases among those who were not fully vaccinated vs those who were fully vaccinated decreased from 11.1 to 4.6 between 2 periods when the prevalence of the delta variant was lower (April 4 to June 19) and higher (June 20 to July 17) when averaged weekly; between the same periods, the IRRs for hospitalizations and deaths decreased from 13.3 to 10.4 and from 16.6 to 11.3, respectively. These findings were consistent with a suggested reduction in vaccine protection against infection and continued protection against COVID-19-associated hospitalization and death.

“The data might be helpful in communicating the real-time impact of vaccines (e.g., persons not fully vaccinated having over 10 times higher COVID-19 mortality risk) and guiding prevention strategies, such as vaccination and nonpharmacologic interventions,” the authors write.

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