THURSDAY, Aug. 26, 2021 (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 Aug. 24 early-release issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.
Jennifer B. Griffin, Ph.D., 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 percent 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 percent were in partially vaccinated persons, and 71.4 percent 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 percent, respectively) compared with partially vaccinated (6.2, 1.0, and 0.3 percent, respectively) and unvaccinated persons (7.6, 1.5, and 0.5 percent, 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 percent), partially vaccinated persons (0 to 88.1 percent), and unvaccinated persons (8.2 to 87.1 percent).
"Ongoing surveillance to characterize postvaccination infections, hospitalizations, and deaths will be important to monitor vaccine effectiveness, particularly as new variants emerge," the authors write.