Q&A: Prosser and team find updated COVID-19 vaccine more cost-effective for older adults
Analysis helped inform recommendations for the vaccines, which led to availability nationwide in early September
The U-M COVID-19 Vaccination Modeling Team prepared a preliminary economic analysis of the updated vaccines against the novel coronavirus for the Centers for Disease Control and Prevention (CDC), and presented it at the June 24, 2024 meeting of the CDC Advisory Committee on Immunization Practices (ACIP). That analysis helped inform ACIP’s recommendations for the vaccines, which led to their availability nationwide in early September.
Lisa Prosser, Ph.D., M.S., led the U-M team’s analysis. Prosser is the Marilyn Fisher Blanch Research Professor of Pediatrics at the U-M Medical School, and a professor in the U-M School of Public Health. She had done previous cost-effectiveness analyses of vaccines against COVID and other conditions, which have been used in setting national vaccine policy for children and adults. She comments on the latest analysis:
What COVID-19 vaccines are available for the 2024–2025 season?
There are three updated COVID-19 vaccines currently available, including mRNA vaccines from Pfizer and Moderna and one protein-based vaccine from Novavax. Our economic analysis does not focus on the individual vaccine products. It focuses on the mRNA vaccines together, considering a generalized mRNA vaccine intervention that incorporates the range of attributes of the available mRNA vaccines.
What is the primary focus of this economic analysis?
The objective of the June 2024 economic analysis is to provide information to the CDC ACIP as they were developing their vaccination recommendations for COVID-19 vaccines for the 2024–25 season. This is the Phase 3 analysis, as we presented two earlier versions of this model to the CDC in September 2023 and February 2024.
This research is the result of collaborative work with the CDC. It is important to note that we do not make recommendations to the ACIP. Instead, we provide information that they will then use as part of their deliberations to make recommendations. The ACIP considers a number of different areas of evidence as part of their practice recommendations, which is summarized in a different part of the presentation to the ACIP.
What age groups did you study?
We evaluated five age groups within the analysis: two pediatric age groups, 5–11 and 12–17 years, and three adult age groups, 18–49, 50–64, and 65 years and older. This is the first economic analysis that includes results for the pediatric age groups.
What methods did you employ?
We used simulation modeling, or computer modeling, to project health and economic outcomes for hypothetical individuals who can travel through the two arms [the intervention arm and the non-intervention arm] of our simulation model.
We modeled the effects of vaccination by having two arms of the simulation model that are identical, but in the intervention arm we reduce the probability of any of those outcomes, including having COVID-19 illness, being hospitalized, or dying from COVID-19 by the effectiveness of vaccination.
We ran hypothetical individuals through the simulation model and then counted up all the outcomes in both arms. By comparing the vaccinated group to the unvaccinated group, we can calculate the benefits of vaccination in terms of both reduced illness, reduced hospitalization, and reduced death, as well as reduced or increased costs because there are costs saved with avoided illnesses but also increased costs due to costs of vaccination.
What calculations were used?
We calculated all the numbers of COVID-19 illness, hospitalization, and death in both arms of the simulation model. We also translated each of those health outcomes into a measure called a quality-adjusted life year (QALY), which can be thought of as equivalent to a year in perfect health. And by using that measure, we can essentially combine the quality-of-life effects of illness, hospitalization, and death into one single measure.
The primary outcome for the analysis is the incremental cost-effectiveness ratio (ICER), which is calculated by subtracting the total costs in the intervention arm from the non-intervention arm and the total quality adjusted life years in the intervention arm from the non-intervention arm. The metric, dollars per QALY, is a very common measure that we use in health economics to understand the value of all types of interventions.
What are the significant findings of this economic analysis?
The analysis shows that vaccination averts illness, hospitalization, and death for all age groups, but with substantial variation in impact by age. We see many more hospitalizations and deaths averted for older individuals compared to younger adults or pediatric age groups.
We do sensitivity analyses to understand the uncertainty associated with the results. In other words, if we change the inputs into the model, such as the effectiveness of vaccination, how much does this change the results? And the conclusion, when looking at the overall level of uncertainty, is that our results are very robust for older age groups, but that there is substantial uncertainty for younger age groups.
We could think about certain types of patients for whom vaccination could be very cost-effective in younger age groups, and for others it would not be cost-effective. Whereas, when we look at individuals 65 and older, we vary those inputs into the simulation model, and that cost-effectiveness looks very favorable for that particular age group.
What does the economic analysis suggest for the pediatric population?
This is the first analysis in which pediatric age groups have been incorporated into the simulation, specifically because the evidence base is so much less robust. Fewer children are getting vaccinated, so there are less data on which to develop the simulation model. So it's important to note that there is a higher degree of uncertainty for these pediatric results compared to the adult age groups.
What is the bottom line?
Age is an essential part of the economic analysis because the effects of COVID-19 illness vary substantially by age group, with much more severe outcomes in terms of critical illness and death for older individuals compared to younger age groups. The results of the economic analysis show that the cost-effectiveness for vaccination is much more favorable for older individuals than for younger individuals.
For individuals age 65 and older, vaccination appears to have favorable cost-effectiveness across many different scenarios. Whereas for younger adults and pediatric age groups, if we run some scenarios that proxy for those that are at higher risk for complications, at higher risk for being hospitalized, or for dying from influenza, the results are favorable for those higher-risk scenarios but less favorable for lower-risk individuals.
How will this analysis move to implementation?
The CDC ACIP reviewed the results from our economic analysis along with other studies focusing on vaccine effectiveness, the burden of illness for COVID-19, safety for the vaccine products, ability to implement the recommendations, as well as other factors. After considering all of those, at the end of the meeting, the ACIP took a formal vote to recommend annual vaccinations for all individuals six months and older.
What was most interesting about the analysis?
This economic analysis is especially interesting because of the differences by age groups. It highlights how much the value of vaccination can vary by age. What we weren't able to incorporate into the economic analysis is the importance of risk status. That is something that we are planning to incorporate into the modeling analysis for next year's recommendations, such as looking at high-risk compared to non-high-risk populations. This analysis also shows that the vaccine would be more cost-effective for the younger age groups at a cost per dose of less than $50.
How will this analysis guide clinicians and patients?
This analysis provides important information on the CDC's guidance for annual vaccinations. Similar to their recommendations for annual influenza vaccinations, these results will be taken into account for clinicians when their patients are coming in for their annual visits. It will also support efforts to provide vaccination clinics in the employer and other settings.
What is the impact on insurers and government healthcare programs?
Having an ACIP recommendation for a vaccine ensures that the vaccine is covered by most insurance plans.