Diabetes Cohort Study Reveals Prolonged Delays in Pneumococcal Vaccination

Adults with diabetes carry a well-documented, elevated risk for invasive pneumococcal disease (IPD); however, a new population-based cohort study published in Vaccine shows that recorded first-dose pneumococcal vaccination among this group remains low and markedly delayed, even in a universal health care system with free-of-charge, risk-based entitlement.¹

Investigators used linked administrative health care databases from the Romagna Local Health Authority in Emilia-Romagna, Italy, to follow 77,138 adults with diabetes—57,113 in a prevalent cohort as of January 2017 and 20,025 newly diagnosed (incident) between 2017 and 2023—through June 30, 2024. Monthly vaccination coverage was estimated using a person-time approach, and time to first recorded pneumococcal vaccination was assessed with Kaplan-Meier and Cox proportional hazards methods, with sensitivity analyses treating death as a competing risk.¹

Coverage Trends Over Time

Recorded pneumococcal vaccination coverage rose from approximately 7.2% in January 2017 to 28% by June 2024. Despite steady growth, coverage never crossed the 30% threshold throughout the 7-year study period.¹

Among the incident cohort, which included individuals newly identified with diabetes, vaccination uptake did not concentrate soon after diagnosis. The cumulative probability of vaccination was just 4.4% at 1 year, and then rose to 12.6% at 3 years, 22.4% at 5 years, and 34.8% at 7 years. The study authors noted that a gradual accumulation, rather than an early spike following diagnosis, is compatible with incomplete integration of pneumococcal vaccination into routine chronic disease care pathways.¹

Predictors of Vaccination Uptake

In multivariable Cox regression, age was the strongest predictor of uptake, peaking among adults aged 60 to 69 years (HR, 7.30; 95% CI, 6.17-8.65) relative to the youngest reference group, a pattern the study authors attributed partly to overlap with Italy's age-based vaccination offer to the cohort turning 65 years.¹

Foreign citizenship was associated with substantially lower uptake (HR, 0.48; 95% CI, 0.43-0.54), while female sex showed a smaller but significant reduction (HR, 0.84; 95% CI, 0.81-0.86). Higher comorbidity burden, measured by the Charlson Comorbidity Index, was associated with modestly higher uptake; however, this association was attenuated when death was treated as a competing risk, suggesting that greater health care contact may create more vaccination opportunities even as higher mortality among sicker patients shortens the window to receive a dose.¹

Why Diabetes Raises Pneumococcal Risk

A 2024 meta-analysis of 36 observational studies found that adults with diabetes face more than double the risk of IPD compared with the general population (unadjusted OR, 2.42; 95% CI, 2.00-2.92) and a higher case-fatality rate (unadjusted OR, 1.61; 95% CI, 1.25-2.07). Chronic hyperglycemia is thought to impair neutrophil function and opsonophagocytosis, heightening susceptibility to pneumococcal infection.²

Evolving Vaccine Recommendations

The Advisory Committee on Immunization Practices (ACIP) has continued to refine adult pneumococcal vaccine guidance during the study's follow-up window. In October 2024, ACIP expanded its recommendation to include a single dose of a pneumococcal conjugate vaccine (PCV) for all adults aged 50 years and older who are vaccine-naïve or have unknown vaccination history, building on the existing risk-based recommendation—which includes diabetes—for adults aged 19 to 49 years. Newer higher-valency conjugate options, including the 21-valent PCV (Capvaxive; Merck & Co), have also entered the adult immunization landscape, with ACIP endorsing it as an additional option for eligible adults.⁴

Implications for Pharmacy Practice

The study authors emphasized that low, delayed uptake should not be attributed to patient hesitancy alone, noting that both individual demand and health system delivery likely contribute, though their relative roles could not be disentangled with the available data.¹

They called for systematic vaccination assessment at predefined points of diabetes care (eg, diagnosis, routine follow-up, specialist visits) to close the gap between formal eligibility and real-world uptake. For pharmacists, who are frequently positioned at points of routine patient contact, the findings reinforce an opportunity to proactively screen and offer pneumococcal vaccination to patients with diabetes rather than relying on reactive requests, particularly outside the narrow window of fall immunization campaigns.¹

REFERENCES

1. Lenzi J, Montalti M, Di Valerio Z, et al. Temporal patterns and potential missed opportunities in pneumococcal vaccination among adults with diabetes: a population-based cohort study. Vaccine. 2026;91:129063. doi: 10.1016/j.vaccine.2026.129063

2. Silverii GA, Gabutti G, Tafuri S, et al. Diabetes as a risk factor for pneumococcal disease and severe related outcomes and efficacy/effectiveness of vaccination in diabetic population. Results from meta-analysis of observational studies. Acta Diabetol. 2024;61(8):1029-1039. doi:10.1007/s00592-024-02282-5

3. Kobayashi M, Leidner AJ, Gierke R, et al. Expanded recommendations for use of pneumococcal conjugate vaccines among adults aged ≥50 years: recommendations of the Advisory Committee on Immunization Practices — United States, 2024. MMWR Morb Mortal Wkly Rep. 2025;74:1-8. doi:10.15585/mmwr.mm7401a1

4. CDC accepts new recommendations for adult pneumococcal vaccine. U.S. Pharmacist. July 18, 2024. Accessed September 2, 2026. https://www.uspharmacist.com/article/cdc-accepts-new-recommendations-for-adult-pneumococcal-vaccine