Evaluating real-world effectiveness and vaccine targeting strategies for the pneumococcal vaccine
A large real-world effectiveness study among more than 450,000 members examined the effectiveness of the pneumococcal vaccine (PPSV23) in protecting against the most severe forms of pneumococcal disease and hospital-treated pneumonia. Different vaccine targeting strategies have also been assessed, with a population-customized risk model demonstrating more precise vaccine targeting and resource allocation than simply using existing international guideline criteria.
Context and Aims
With the conjugate pneumococcal vaccine available as an alternative to the PPSV23 for pneumococcal disease prevention in adults, and the clinical efficacy of pneumococcal vaccines in question for preventing all-cause pneumonia, decisions about the extent of coverage and appropriate target populations for vaccination face health care managers and decision-makers.
Pneumococcal disease can present in various forms, from less severe community-treated pneumonia to more severe manifestations such as hospital treated pneumonia and invasive pneumococcal disease (IPD). This project aims to determine the vaccine’s effectiveness of preventing disease in the real-world setting and to identify in which sub-populations vaccine outreach should target by comparing various vaccine strategies.
The real-world effectiveness of the PPSV23 was evaluated using propensity score analyses and matching techniques to adjust for underlying differences between cases and non-cases, among more than 450,000 members aged 65 years and older in Clalit. Effectiveness was assessed for IPD and hospital-treated pneumonia.
For comparing vaccine targeting strategies the following analyses were conducted:
- Develop a population-customized risk model among more than 1 million Clalit members aged 50 years and older, considering risk factors such as age, sex, socioeconomic status, smoking status, and comorbidity burden
- Validate model in test sample
- Assign each member a risk score based on the risk model
- Compare the predictive ability of the customized risk model to risk groups defined according to internationally-recognized criteria for immunization practices, using various cut points of the customized model
- Assessments of vaccine strategies include representations of varying resource availability and compare utilizing a customized model vs. ACIP-based criteria
Key Findings and/or Potential Impact
The Clalit Research Institute found that while the pneumococcal vaccine (PPSV23) is highly effective at preventing invasive disease, there appears to be no measurable effectiveness in preventing hospital-treated pneumonia. Vaccination policy, particularly in consideration of new vaccinations against additional strains, will need to balance the benefit or preventing the rarer severe disease with the more common milder forms.
More precise and strategic targeting of vaccine administration can be achieved through utilizing clinical and administrative health record databases to create population-specific risk stratification models.
Leventer-Roberts M, Feldman BS, Brufman I, Cohen-Stavi CJ, Hoshen M, Balicer RD. Effectiveness of 23-valent pneumococcal polysaccharide vaccine against invasive disease and hospital-treated pneumonia among people aged ≥65 years: a retrospective case-control study. Clinical Infectious Diseases, 2015. 60(10): p. 1472-80.