Alliance for Pandemic Preparedness

February 1, 2021

The Impact of Vaccination on COVID-19 Outbreaks in the United States

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A modeling study evaluating the impact of a 2-dose COVID-19 vaccination campaign in the US showed that over a period of 300 days, vaccinating 40% of the population in sequential priority groups reduced the overall attack rate from 9% (without vaccination) to 4.6%, with the greatest relative reductions among those aged 65 and older. Modeled scenarios prioritized healthcare workers and high-risk individuals and did not include vaccinations for children under 18. Vaccination reduced adverse outcomes, with non-ICU hospitalizations, ICU hospitalizations, and deaths decreasing by 63.5%, 65.6%, and 69.3%, respectively. The model assumed a vaccine efficacy of 95%, an existing population immunity level of 10%, and a SARS-CoV-2 reproductive number of 1.2.

Moghadas et al. (Jan 30, 2021). The Impact of Vaccination on COVID-19 Outbreaks in the United States. Clinical Infectious Diseases. https://doi.org/10.1093/cid/ciab079