Routine vaccinations in the United States (US) generate substantial benefits by preventing an estimated 40,000 premature deaths with a net economic savings greater than $68.8 billion, among the cohort born in 2009 [1]. Since 1964, the Advisory Committee on Immunization Practices (ACIP) makes recommendations to the Centers for Disease Control and Prevention on the routine use of vaccines and related immunization pharmacological products in the US [2]. Part of ACIP deliberations on the recommended use of an immunization product considers the benefits and costs of vaccination strategies, estimated with cost-effectiveness models [3].

Identifying the most appropriate value for a cost per vaccine dose input in an economic model requires careful consideration of the objectives and perspective of the economic model [4]. In the case of a pre-market vaccine, a price or price range for the vaccine is often provided by the manufacturer. For simplicity and because future trends in the cost of the vaccine are unknown, models typically assume the cost per dose of the vaccine is constant in inflation-adjusted terms throughout the time horizon of the model.

Health care costs and pricing in the US are complex [5] and are generally not transparent [6]. At least three kinds of real-world costs may be relevant for economic decision-making in health care, including: (1) the list price or wholesale price of a product or service, (2) the contracted price, which is the negotiated price of a product, service, or group of either products or services between government agencies, health care systems or providers and the product manufacturers, and (3) the reimbursement for health care services paid by private insurance or public payers, such as Medicare and Medicaid.

The purpose of this study was to investigate the inflation-adjusted price trends of ACIP recommended vaccines using the manufacturers’ listed price and CDC contracted price as reported on the CDC Vaccine Price List (Price List). The CDC contracted price on the Price List documents the costs paid by federal vaccine contracts. The proportion of vaccines administered under the CDC pricing varies by vaccine. For example, the CDC administered Vaccines for Children (VFC) federal program provides no cost vaccines for eligible children. In 2014, an estimated 50 % of all children in the U.S. were VFC eligible [7]. The trends of the two reported vaccine prices can be used to assess the reasonableness of an assumption of constant future costs per dose of vaccines and can inform best practices for cost-effectiveness analyses of vaccines, whether done pre-market or post-market introduction.

An increase was observed for many vaccines for both private (32 of 50, or 64 %, Table 1, Fig. 1) and CDC costs (36 of 51, or 71 %, Table 2). Negative changes in cost per year was observed for the remaining vaccines. Adult vaccines had larger average annual percent increase in private cost (1.4 %) than pediatric vaccines (0.9 %) (Table 3). Among pediatric vaccines, the HPV vaccine Gardasil^®9 had the largest change in costs per year in private cost ($9.25, 4.1 % increase per year) and in the CDC cost ($7.89, 4.3 % increase per year). Among adult vaccines, Gardasil^®9 had the largest change in cost per year in private cost ($9.03, 4.0 % increase per year) and the pneumococcal vaccine Pneumovax^®23 had the largest change in cost per year in CDC cost ($4.66, 10.0 % increase per year). Vaccines with the largest declines in costs include the Hib vaccine Hiberix^® ($1.21, 6.0 % decrease per year), and the meningococcal vaccine Bexsero^® ($2.59, 1.9 % decrease per year, adult only) which declined the most in cost per year in private and CDC cost, respectively.

Vaccines added to the CDC Price List in 2010 or later had 2.6 % and 1.5 % annual increase in private and CDC costs, respectively. In contrast, vaccines added to the CDC Price List before 2010 had an average 0.04 % and 0.5 % annual increase in private and CDC costs, respectively. Additional sensitivity analyses did not impact findings and are included in the supplementary materials.

In this study, many vaccines’ costs increased more than the PCE health care rate of inflation, i.e., faster than other health care services that are captured in the PCE index. The annual change in costs was greater for products that were added to the Price List in 2010 or later compared to products added earlier, while vaccines with the greatest increase in cost were not always the most expensive. These findings have important implications for cost-effectiveness analyses best practices, and public-health programs.

For cost-effectiveness analyses of vaccines in the US, our findings suggest that multi-year vaccination programs can underestimate the long-term costs of vaccination when assuming a constant vaccine cost per dose. Price increases for vaccines included in the pediatric vaccine schedule accounted for a 19.5 % increase in the overall vaccine purchase cost per child over a 18 year period (1996 to 2014) [14]. This is similar to observed increases in per capita excess medical cost for diabetes over a 10 year period, which was 22 % between 2007 and 2017, and 18 % between 2012 and 2022 [15,16]. Higher vaccine costs (that are constant through time) are typically assessed in the sensitivity analyses of cost-effectiveness models, but for newly introduced vaccines it may be reasonable to include a scenario with an increasing inflation-adjusted cost per dose in addition to an appropriate discount rate to the costs and benefits occurring in the future [17]. Further, our results suggest CEAs could be periodically updated to understand vaccines’ cost-effectiveness over their lifespans. If the cost of a vaccine increases faster than other health care costs, then previous assessments of cost-effectiveness of vaccines could be too favorable, relative to a more up-to-date assessments that incorporate recent changes in costs.

About one third of vaccines examined in this study exhibited decreasing costs, which occurs if a vaccine’s yearly cost increase is less than the rate of inflation. A previous study found a set of specific vaccines that were subject to a price cap did not experience increasing CDC costs per dose over time [18]. In general, costs per dose that are decreasing or stable over time would be less of a concern than increasing costs per dose for vaccination programs and decision makers, because decreasing costs per dose yields lower program expenditures and better economic value for public health systems. On the other hand, increasing costs per dose can be a major obstacle for effective public health programs, like the entitlement VFC or discretionary Section 317 immunization programs. If these programs receive funding that is constant through time while vaccine dose costs increase through time, then the amount of vaccine doses that could be purchased in future years and, by extension, the number of individuals that can be vaccinated would decrease. This decreased ability to provide routine or outbreak response vaccinations could place additional financial strain on immunization programs. Better anticipating future changes to vaccine cost can help vaccine programs and decision makers ensure adequate budget projections to meet program needs.

This study considered the manufacturer reported and the negotiated CDC cost per vaccine dose. We did not gather other contracted costs with the manufacturers, or payer costs based on health insurance claims data. Previous studies have reported the proportion of vaccine private insurance reimbursements exceeding the private List Price ranges from 95 % (pediatric HPV) to as little as 25 % (adult Td) of claims by vaccine [19,20]. This would be an important area for future research along with causal analysis focused on understanding the factors contributing to observed differences in changes in cost per dose by vaccine, age group, year of introduction, etc. Future studies could also examine factors that affect negotiated vaccine prices internationally, and the potential influence of ACIP cost-effectiveness considerations on vaccine prices in the U.S.

To summarize, inflation-adjusted costs of vaccines have increased, on average, and larger annual increases were among vaccines introduced in 2010 or later than vaccines introduced before 2010. These vaccine cost changes highlight the limitations of a constant vaccine cost assumption used in many economic models, especially for new vaccines. These findings can inform cost-effectiveness analyses of long-term vaccination programs and policy.