Updated ‘23–‘24 COVID-19 Vaccine Protects Adults but Comes at High Cost for Older and High-Risk Groups

A single dose of the 2023–2024 COVID-19 mRNA vaccine prevented significant illness and death across age groups; however, its economic value was higher for older adults and higher-risk populations, according to a recent study published in JAMA Network Open.

While ongoing prevention efforts occur, COVID continues to cause significant illness and death among adults. In 2020 and 2021, the FDA authorized two mRNA vaccines, Moderna and Pfizer-BioNTech, for emergency use to prevent severe COVID. In September 2023, these monovalent COVID vaccines for the 2023–2024 season were approved.

Around the same time, the CDC’s Advisory Committee on Immunization Practices (ACIP) reviewed recommendations for their use, with an additional review in February 2024.

This study aimed to support ACIP decisions on seasonal COVID vaccination by estimating the annual disease burden, healthcare use and cost-effectiveness of vaccinating adults aged 18 and older compared with not receiving the updated vaccine.

A second phase evaluated the potential benefits of an additional midyear dose, focusing on the incremental effectiveness and economic value of a second 2023–2024 COVID-19 mRNA vaccine dose for U.S. adults.

Results from a recent case-control study support these findings.

The study examined medically attended COVID-like illness from September 2023 to August 2024 and found that the 2023–2024 vaccines reduced emergency and urgent care visits, hospitalizations and critical illness among adults 18 years and older. It was found that vaccine effectiveness was highest and most durable against critical illness, especially for adults 65 and older, reflecting the added protection beyond prior infection or previous vaccination.

The study also highlighted that vaccines containing the monovalent XBB.1.5 component offered stronger protection when other variants closely matched the vaccine. In addition, a second dose appeared to provide extra protection for older adults, particularly those at higher risk.

For U.S. adults, a single dose is projected to prevent substantial illness and death, with hospitalizations avoided ranging from 39 per 100,000 among adults 18 to 49 years old to 391 per 100,000 in those 65 and older and deaths prevented ranging from 1.4 to 43.4 per 100,000.

The number of COVID cases prevented was about the same for all age groups, ranging from roughly 7,600 to 9,000 per 100,000 people.

Cost analyses showed that vaccination was most cost-effective for older adults, with vaccination being cost-saving for those 65 and older. Adults 50 to 64 years had an incremental cost-effectiveness ratio (ICER) of $25,787 per quality-adjusted life year (QALY) and adults 18 to 49 years had an ICER of $115,588 per QALY. ICERs for younger adults were highly sensitive to vaccine effectiveness, dose cost, and hospitalization risk, while ICERs for older adults remained robust.

It was also found that a two-dose strategy was generally not cost-effective for adults under 65 but became favorable for adults 65 and older, especially higher-risk individuals or when the dose cost was below $50.

Supporting the study results are standout strengths that include the use of a decision analytic model to evaluate both health and economic outcomes, updated hospitalization data and sensitivity analyses across multiple parameters.

Limitations include reliance on unpublished data, exclusion of some Medicare-only populations and limited long COVID and pediatric data.

Study authors recommend ongoing updates to the model with current vaccine effectiveness, pediatric data and transmission effects to update future evaluations.