High Burden of PCV21 Strains in Norway Shows Need for Effective US Vaccination Strategies

Compared with the pneumococcal 20-valent conjugate vaccine (PCV20) and pneumococcal 23-valent polysaccharide vaccine (PPSV23), serotypes covered by the pneumococcal 21-valent conjugate vaccine (PCV21, Capvaxive; Merck & Co.) are associated with a larger economic health burden in Norway, according to an analysis published by investigators in Infectious Diseases and Therapy. The results demonstrate the need for more prolific PCV21 vaccination in the United States as other developed countries grapple with the spread of Streptococcus pneumoniae (S pneumoniae) serotypes covered by the vaccine.¹

Were PCV21 Serotypes Associated With a Higher Burden for Patients?

The investigators utilized a published Markov model, adapted to the Norwegian health care system, to determine invasive pneumococcal disease (IPD) cases, deaths, and direct medical costs associated with PCV21, PCV20, and PPSV23 serotypes. The analysis included adults aged 65 and older, adults aged 50 through 64 years, and individuals aged 18 through 64 years with risk factors for severe IPD.¹

Disease Burden

First, the burden of disease was quantified. Across all age groups, the number of pneumococcal disease cases attributable to PCV21 serotypes was greater than the number of cases attributable to PCV20 and PPSV23 serotypes at all risk levels.¹

For adults aged 65 and older, there was a 41% increase in IPD cases attributed to PCV21 serotypes versus PCV20 serotypes and a 26% increase in cases versus PPSV23 serotypes. For adults aged 50 through 64 years, there were 39% more IPD cases attributable to PCV21 serotypes than PCV20 serotypes and 25% more than PPSV23 serotypes. Additionally, for adults aged 18 through 64 years with risk factors, IPD cases from PCV21 serotypes accounted for 37% more cases versus PCV20 serotypes and 22% more cases versus PPSV23 serotypes.¹

Cumulatively, among all age groups, 25% of cases were attributable to the 8 unique S pneumoniae serotypes unique to PCV21. There was a greater projected number of deaths attributable to PCV21 serotypes in all age groups and at all risk levels than deaths attributable to PCV20 and PPSV23 serotypes.¹

Economic Burden

The lifetime economic burden of pneumococcal disease due to serotypes of PCV21, PCV20, and PPSV23 was determined. Serotypes included in the PCV21 vaccine were associated with a higher economic burden compared with PCV20 and PPSV23 serotypes, with the model estimating that lifetime direct treatment costs for pneumococcal disease attributable to PCV21 serotypes were 3.9 billion Norwegian kroner (NOK) in adults aged 65 and older. The lifetime burden was 3.5 billion NOK in adults aged 50 through 64 years and 4.4 billion NOK in adults aged 18 through 64 with risk factors.¹

This can be compared with the estimated lifetime direct costs associated with PCV20 and PPSV23 serotypes. These costs were 2.8 billion NOK and 3.1 billion NOK in adults aged 65 and older; 2.5 billion NOK and 2.8 billion NOK in adults aged 50 through 64; and 3.2 billion NOK and 3.6 billion NOK for adults aged 18 through 64 with risk factors for PCV20 and PPSV23 serotypes, respectively.¹

According to the authors, within each age group, patients with the highest risk had the highest associated total direct lifetime costs.¹

What Should Pharmacists in the United States Take From This Data?

There is a clear and present burden due to serotypes protected by the PCV21 vaccine, specifically the 8 serotypes that are unique to the vaccine. As newer vaccines continue to be developed and proliferated, new serotypes will continue to emerge as major threats to patients. The situation is similar in the US, as serotypes unique to PCV21 are more prevalent among US adults with pneumococcal disease than serotypes unique to PCV20.^1,2

As serotypes evolve and their circulation shifts due to indirect protection and immunization throughout the population, it remains critical to reevaluate serotypes included in the most updated vaccines and quantify the burden of pneumococcal disease due to such serotypes. Pharmacists are essential members of the health care team in the immunization and infectious disease settings and can counsel patients or caregivers on the benefits of receiving the most up-to-date pneumococcal vaccine for protection against circulating serotypes that can cause severe IPD.^1,2

REFERENCES

1. Yi Z, Tajik AA, Klitkou S, et al. Estimating the health and economic burden of pneumococcal diseases attributable to PCV21 versus PCV20 or PPSV23 serotypes among adults in Norway. Infect Dis Ther. Published Online December 10, 2025. doi:10.1007/s40121-025-01275-3

2. Halpern L. PCV21-unique serotypes most prevalent in US adults with pneumococcal disease. Pharmacy Times. Published November 5, 2025. Accessed December 17, 2025. https://www.pharmacytimes.com/view/pcv21-unique-serotypes-most-prevalent-in-us-adults-with-pneumococcal-disease