mRNA Vaccine Effectiveness Against Coronavirus Disease 2019 Hospitalization Among Solid Organ Transplant Recipients

Background The study objective was to evaluate 2 and 3 dose COVID-19 mRNA vaccine effectiveness (VE) in preventing COVID-19 hospitalization among adult solid organ transplant (SOT) recipients. Methods 21-site case-control analysis of 10,425 adults hospitalized March-December 2021. Cases were hospitalized with COVID-19; controls were hospitalized for an alternative diagnosis (SARS-CoV-2 negative). Participants were classified as: SOT recipient (n=440), other immunocompromising condition (n=1684), or immunocompetent (n=8301). VE against COVID-19 associated hospitalization was calculated as 1–adjusted odds ratio of prior vaccination among cases compared with controls. Results Among SOT recipients, VE was 29% (95% CI: -19 to 58%) for 2 doses and 77% (95% CI: 48 to 90%) for 3 doses. Among patients with other immunocompromising conditions, VE was 72% (95% CI: 64 to 79%) for 2 doses and 92% (95% CI: 85 to 95%) for 3 doses. Among immunocompetent patients, VE was 88% (95% CI: 87 to 90%) for 2 doses and 96% (95% CI: 83 to 99%) for 3 doses. Conclusion Effectiveness of COVID-19 mRNA vaccines was lower for SOT recipients than immunocompetent people and those with other immunocompromising conditions. Among SOT recipients, vaccination with 3 doses of an mRNA vaccine led to substantially greater protection than 2 doses.