BACKGROUND: Immunocompromised patients and those with certain underlying medical conditions are at risk of pneumococcal disease, but in France their vaccine coverage is largely unknown. We aimed to assess the number of adult patients eligible for pneumococcal vaccination in France. METHODS: We conducted an annual cross-sectional study based on retrospective data from the French National Health Data System. Over 2014-2018, we included all adults continuously affiliated to the General health insurance scheme (covering 76% of the population), at risk of pneumococcal disease. Patients were identified with published or newly developed algorithms using diagnoses and reimbursements for hospital stays, medical procedures, and specific treatments, laboratory tests, or medical devices. RESULTS: On January 1, 2018, we identified 4,045,021 at-risk patients (11% increase since 2014). Mean age was 66.1years (55.1% were aged≥65), 51% were men, and 18% had at least two conditions. Of these, 3,634,594 had a chronic medical condition (including 2,617,921 patients treated for diabetes, 616,003 for chronic respiratory disease, 424,223 for heart failure, and 285,214 for chronic liver disease) and 570,035 were immunocompromised (of these, 191,527 were treated with immunosuppressive drugs or biotherapy, 152,255 with chemotherapy for cancer, and 100,604 for HIV). CONCLUSION: These published or newly developed algorithms - which can be used to address other public health issues - identified more than 4 million adults eligible for pneumococcal vaccination in the main health insurance scheme (10% of the studied adult population). This is a first step towards ensuring patients get vaccinated as part of their chronic condition management.