Pneumococcal vaccination coverage and adherence to recommended dosing schedules in adults: a repeated cross-sectional study in the INTEGO morbidity registry

Arne Janssens, Chloé Abels, Barbara Merckx, André Bento Abreu, Bert Vaes

Keywords: general practice, adult pneumococcal vaccination, coverage rate, equity

Background:
Belgium’s Superior Health Council (SHC) recommends pneumococcal vaccination for adults aged 16+ at high risk, 50-85 years with comorbidities, and healthy elderly aged 65-85 years, with specific vaccine administering sequence and timing (i.e., schedules). Currently there is no publicly funded adult pneumococcal vaccination program in Belgium.

Research questions:
This study investigated the seasonal pneumococcal vaccination trends, evolution of vaccination coverage rates (VCR) and adherence to SHC recommendations.

Method:
INTEGO is a general practice morbidity registry in Flanders (Belgium) representing 104 general practice centers and 226.793 patients in 2021. A repeated cross-sectional study for the period 2016-2021 was performed. To assess the association between (schedule adherent) pneumococcal vaccination status and patient characteristics (gender, age, comorbidity, influenza vaccination status and socio-economic status), adjusted odds ratios (aORs) were computed using multivariate logistic regression.

Results:
Pneumococcal VCR in Flanders showed a seasonal trend with a PCV13 peak in November (together with seasonal flu vaccination) and a PPV23 peak in January. The VCR in the population at risk increased from 18% in 2016 to 24% in 2021 (one-sided p = 2.2-16). VCR was highest for high-risk adults (29%), followed by the 50-to-85-year-olds with comorbidities (22%) and healthy elderly (15%). For persons with a lower socio-economic status, the aOR was 1.06 (95%CI 1.04;1.09) for immunization and 1.23 (95%CI 1.18;1.28) for schedule non-adherence. The aOR for schedule non-adherence was 0.51 (95%CI 0.49;0.54) for the 50-to-85-year-olds with comorbidities and 0.52 (95%CI 0.5;0.55) for healthy elderly compared to the high-risk group.

Conclusions:
General practice data from Flanders showed that VCR of target groups is slowly increasing, while displaying seasonal peaks. However, high-risk patients and adults with poor socio-economic status have lower odds of schedule adherence, which demonstrates the need for a publicly funded program in Belgium to ensure equitable access and to optimize the benefits of current recommendations for the target population.

Points for discussion:
Since we only used registered vaccines to determine a patient’s vaccination status and since not all vaccinations might be registered, vaccination coverage rates might slightly be underestimated.

Sensitivity analysis, including generalized linear mixed models and datasets with imputed smoking status, showed robustness of the results.

Although most European countries have a government funded program for pneumococcal vaccines, Belgium has not. This study demonstrates the need for a publicly funded program in Belgium to ensure equitable access. Additionally, a previous study within our group showed that pneumococcal vaccination protects against severe lower respiratory tract infections, which emphasizes the importance of such a program.