From December 2020-September 2021, approximately 27 million COVID-19 infections, 1.6 million hospitalizations, and 235000 deaths were prevented by vaccination.
Before the COVID-19 vaccine rollout, there were an estimated 16 million confirmed infections and 310000 related deaths in the US. By the end of September 2021, approximately 67% of adults and 83% of adults over 65 years were fully vaccinated with an authorized COVID-19 vaccine.
COVID-19 morbidities and mortalities avoided through the direct protection of vaccinated individuals is unclear. Thus, one JAMA Network Open study estimated the COVID-19 infections, hospitalizations, and deaths prevented among vaccinated adults in the US.
The modeling study utilized a multiplier to infer the avoided number of COVID-19 infections and deaths from December 1, 2020-September 30, 2021. These data were extrapolated from COVID-19-associated hospitalizations, stratified by US state, month, and age group (18-49; 50-64; ≥65 years).
The estimates were combined with available information of vaccine coverage and efficacy. The study authors explained, “To estimate the expected burden of COVID-19 in the absence of vaccination, we multiplied the estimated risks of infection, hospitalizations, and deaths for each age group, month, and state by the estimated numbers of susceptible individuals in each equivalent age group, month, and state in the absence of vaccination. The prevented burden of COVID-19 was calculated as the difference between expected outcomes in the absence of vaccination and the observed burden with vaccination.”
Notably, 2 major case surges occurred during this study period. The program began during the peak of the COVID-19 wave during winter 2020, and continued through the rise of the highly infectious Delta variant in June 2021.
From December 1, 2020-September 30, 2021, the investigators calculated that COVID-19 vaccination prevented approximately 27 million infections, 1.6 million hospitalizations, and 235000 deaths in the US.
Thus, vaccination prevented 30% of all expected infections, 33% of all expected hospitalizations, and 34% of all expected deaths in US adults.
Most of the prevented deaths were among those 65 years and older, with an avoided 75900 hospitalizations and 154000 deaths.
For the month of September 2021 alone, fully vaccinated adults were predicted to have avoided 52% of expected infections, 56% of expected hospitalizations, and 58% of expected deaths.
The investigators concluded that the US COVID-19 vaccine rollout prevented a significant burden of morbidity and mortality by granting direct protection to vaccinated persons. They wrote, “This study is among the first, to our knowledge, to present estimates of age group–specific impacts of vaccination among vaccinated persons in the US over time and by US Department of Health and Human Services (HHS) region.”