| Methods |
Matched case‐control study |
| Participants |
Adults aged 18 years and above with indication for vaccination or above 65 years (n = 180) |
| Interventions |
Cases (n = 90) hospitalised with IPD from 1978 to 1982 (no previous pneumococcal disease)
Controls (n = 90) selected from roster of hospitalised patients with no previous episode of pneumonia
14‐valent PPV |
| Outcomes |
B1. IPD (immunocompetent and immunocompetent elderly) |
| Notes |
Matched 1:1 according to age, date of hospitalisation, condition identified and vaccination indication (duration, severity and number of illnesses)
Vaccination history reviewed from 1978 onwards
Vaccinated defined as receiving dose at least 2 weeks prior to selected hospitalisation (14‐valent PPV) |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
High risk |
Non‐random study |
| Allocation concealment (selection bias) |
Low risk |
Study investigators determining participant inclusion unlikely to be aware of vaccination status |
| Confounding
All outcomes |
Low risk |
2/6 important confounding factors considered, however critical factors covered |
| Blinding of participants and personnel (performance bias)
All outcomes |
Unclear risk |
NA |
| Blinding of outcome assessment (detection bias)
All outcomes |
Low risk |
Due to specificity of the outcome |
| Incomplete outcome data (attrition bias)
All outcomes |
Unclear risk |
Not described |
| Selective reporting (reporting bias) |
Low risk |
Limited extent to which analysis could have been manipulated to bias the findings |
