COVID-19 deaths and hospitalizations averted by rapid vaccination rollout in the United States

Moghadas, S.; Sah, P.; Fitzpatrick, M. C.; Shoukat, A.; Pandey, A.; Vilches, T. N.; Singer, B. H.; Schneider, E. C.; Galvani, A. P.

Importance: Randomized clinical trials have shown that the COVID-19 vaccines currently approved in the US are highly efficacious. However, more evidence is needed to understand the population-level impact of the US vaccination rollout in the face of the changing landscape of COVID-19 pandemic in the US, including variants with higher transmissibility and immune escape. Objective: To quantify the population-level impact of the US vaccination campaign in averting cases, hospitalizations and deaths from December 12, 2020 to June 28, 2021. Design: Age-stratified agent-based model which included transmission dynamics of the Alpha, Gamma and Delta variants in addition to the original Wuhan-1 variant. Setting: Our model was calibrated to COVID-19 outbreak and vaccine rollout in the US. Model predictions were made at the country level. Participants: Simulated age-stratified population representing US demographics. Main Outcomes and Measures: Cases, hospitalizations and deaths averted by vaccination against COVID-19 in the US, compared to the counterfactuals of no vaccination and vaccination administered at half the actual pace. Results: The swift vaccine rollout in the US curbed a potential resurgence of cases in April 2021, which would have been otherwise fuelled by the Alpha variant. Compared to the scenario without vaccines, we estimated that the actual vaccination program averted more than 26 million cases, 1.2 million hospitalizations and saved 279,000 lives. A vaccination campaign with half the actual rollout rate would have led to an additional 460,000 hospitalizations and 121,000 deaths. Conclusions and Relevance: The COVID-19 vaccination campaign in the US has had an extraordinary impact on reducing disease burden despite the emergence of highly transmissible variants. These findings highlight that the pace of vaccination was essential for mitigating COVID-19 in the US, and underscore the urgent need to close the vaccine coverage gaps in communities across the country.