The potential clinical impact of implementing different COVID-19 boosters in fall 2022 in the United States.

OBJECTIVE: Emerging SARS-COV-2 variants are spurring the development of adapted vaccines as public health authorities plan for fall vaccinations. This study estimated the number of infections and hospitalizations prevented by three potential booster strategies for adults (≥18 years) in the United States: boosting with either Moderna's (1) licensed first generation monovalent vaccine mRNA-1273 (ancestral strain) or (2) candidate bivalent vaccine mRNA-1273.214 (ancestral + BA.1 variant of concern [VOC]) starting in September 2022, or (3) Moderna's updated candidate bivalent vaccine mRNA-1273.222 (ancestral + BA.4/5 VOC) starting November 2022 due to longer development time. METHODS: An age-stratified, transmission dynamic, Susceptible-Exposed-Infection-Recovered (SEIR) model, adapted from previous literature, was used to estimate infections over time; the model contains compartments defined by SEIR and vaccination status. A decision tree was used to estimate clinical consequences of infections. Calibration was performed so the model tracks the actual course of the pandemic to present time. RESULTS: Vaccinating with mRNA-1273(Sept), mRNA-1273.214(Sept), and mRNA-1273.222(Nov) is predicted to reduce infections by 34%, 40%, and 18%, respectively, and hospitalizations by 42%, 48%, and 25%, respectively, over 6 months compared to no booster. Sensitivity analyses around transmissibility, vaccine coverage, masking, and waning illustrate that boosting with mRNA-1273.214 in September prevented more cases of infection and hospitalization than the other vaccines. LIMITATIONS AND CONCLUSIONS: With the emergence of new variants, key characteristics of the virus that affect estimates of spread and clinical impact also evolve, making parameter estimation difficult. Our analysis demonstrated that boosting with mRNA-1273.214 was more effective over 6 months in preventing infections and hospitalizations with a BA.4/5 subvariant than the tailored vaccine, simply because it could be deployed 2 months earlier. We conclude that there is no advantage to delay boosting until a more effective BA.4/5 vaccine is available; earlier boosting with mRNA-1273.214 will prevent the most infections and hospitalizations.

An Economic Comparison of Influenza Vaccines Recommended for Use in Eligible Adults under 65 Years in the United Kingdom.

Background: In the United Kingdom (UK), a cell-based quadrivalent influenza vaccine (QIVc) and a recombinant vaccine (QIVr) are recommended for eligible adults under 65 years. The objective of this analysis was to determine the potential cost-effectiveness of QIVc compared to QIVr for this age group using a range of assumptions about relative vaccine effectiveness (rVE). Methods: A dynamic transmission model, calibrated to match infection data from the UK, was used to estimate the clinical and economic impact of vaccination across 10 influenza seasons. The list price was £12.50 for QIVc and £22.00 for QIVr. The base case effectiveness of QIVc was 63.9%. As there are no data comparing the vaccines in the 18 to 64-year-old age group, rVE was varied. Results: For the base case, the rVE of QIVr compared with QIVc must be at least 25% in order for the cost per quality-adjusted life-year gained to be £20,000 or lower. Sensitivity analysis demonstrated that the rVE required for QIVr to be cost-effective was most dependent on the absolute effectiveness of QIVc. Conclusion: At list prices, our analysis predicts that the rVE for QIVr must be at least 25% compared to QIVc in order to be considered cost-effective.

The Cost-Effectiveness of Expanding Vaccination with a Cell-Based Influenza Vaccine to Low Risk Adults Aged 50 to 64 Years in the United Kingdom.

BACKGROUND: In response to COVID-19, the UK National Health Service (NHS) extended influenza vaccination in 50- to 64-year-olds from at-risk only to all in this age group for the 2020/21 season. The objective of this research is to determine the cost-effectiveness of continuing to vaccinate all with a quadrivalent cell-based vaccine (QIVc) compared to returning to an at-risk only policy after the pandemic resolves. METHODS: A dynamic transmission model, calibrated to match infection data from the UK, was used to estimate the clinical and economic impact of vaccination across 10 influenza seasons. The base case effectiveness of QIVc was 63.9% and the list price was GBP 9.94. RESULTS: Vaccinating 50% of all 50- to 64-year-olds with QIVc reduced the average annual number of clinical infections (-682,000), hospitalizations (-5800) and deaths (-740) in the UK. The base case incremental cost per quality-adjusted life-year gained (ICER) of all compared to at-risk only was GBP6000 (NHS perspective). When the cost of lost productivity was considered, vaccinating all 50- to 64-year-olds with QIVc became cost-saving. CONCLUSION: Vaccinating all 50- to 64-year-olds with QIVc is likely to be cost-effective. The NHS should consider continuing this policy in future seasons.