OBJECTIVES: Immunocompromised (IC) individuals and those aged ≥65 years are considered at high risk of severe disease following COVID-19 infections. In Japan, COVID-19 vaccines have been recommended to protect these vulnerable populations. Recent analyses found the Moderna mRNA vaccine more effective in preventing medical encounters following COVID-19 infections than the Pfizer-BioNTech vaccine in both populations (e.g., relative risk for hospitalization of 0.83 in IC individuals). The objectives of the study were to separately estimate the impact of differential vaccine effectiveness on clinical outcomes and treatment costs for individuals aged ≥65 years, and IC individuals aged ≥18 in the Tokyo prefecture.

METHODS: A decision-analytic model was used to predict clinical and economic outcomes of vaccinating with either the Moderna or Pfizer-BioNTech COVID-19 vaccines over a 1-year time horizon. Base-case and low to high infection incidence scenarios were created based on the observed incidence in Tokyo during the Omicron period. Fall 2023 vaccine coverage was estimated from previous vaccines. Consequences of infection (outpatient and hospitalizations, myocarditis, death, long-COVID) and COVID-19 treatment costs were calculated.

RESULTS: Considering the base-case and low to high incidence scenarios, vaccinating persons aged ≥65 years with the Moderna vaccine could prevent additional COVID-19 outcomes compared with the Pfizer-BioNTech vaccine: 1,500 (1,120–1,870) hospitalizations, 120 (90-150) deaths and 1,170 (880-1,460) cases of long COVID. The reduced morbidity corresponds to ¥0.94B-¥1.56B in treatment costs saved. Compared to the Pfizer-BioNTech vaccine, the Moderna vaccine could prevent an additional 550 (420-690) hospitalizations, 46 (35-58) deaths, and 480 (360-600) cases of long-COVID in the IC population, saving ¥344M-¥573M in treatment costs.

CONCLUSIONS: Vaccinating those aged ≥65 years and IC individuals aged ≥18 years with the Moderna vaccine in the Tokyo prefecture is estimated to prevent more cases of COVID-19 related hospitalizations, deaths, and long-COVID, and associated treatment costs compared with the Pfizer-BioNTech vaccine.