HealthDay News — Vaccination protects against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and hospitalization during a period with increasing predominance of the delta variant, according to research published in the early-release issue of the US Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Jennifer B Griffin, PhD, from the Los Angeles County Department of Public Health, and colleagues used COVID-19 surveillance and California Immunization Registry 2 data to describe age-adjusted infection and hospitalization rates during May 1 to July 25, 2021, by vaccination status.

The researchers found that 25.3% of 43,127 reported SARS-CoV-2 infections in Los Angeles County residents aged 16 years and older were in fully vaccinated persons, 3.3% were in partially vaccinated persons, and 71.4% were in unvaccinated persons. The percentages of persons infected with SARS-CoV-2 who were hospitalized, admitted to the intensive care unit, and required mechanical ventilation were lower for fully vaccinated persons (3.2%, 0.5%, and 0.2%, respectively) compared with partially vaccinated (6.2%, 1.0%, and 0.3%, respectively) and unvaccinated persons (7.6%, 1.5%, and 0.5%, respectively). Compared with fully vaccinated persons, the SARS-CoV-2 infection rate and hospitalization rate among unvaccinated persons was 4.9 and 29.2 times higher, respectively, on July 25, 2021. The percentages of B.1.617.2 (delta) variant infections increased during May 1 to July 25 among fully vaccinated persons (8.6% to 91.2%), partially vaccinated persons (0% to 88.1%), and unvaccinated persons (8.2% to 87.1%).

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“Ongoing surveillance to characterize postvaccination infections, hospitalizations, and deaths will be important to monitor vaccine effectiveness, particularly as new variants emerge,” the authors write.

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