OBJECTIVES: The objective was to estimate the number of patients in Germany who received a 4-valent vaccine in 2011. This estimation was based on data collected through a sample of GP/Pediatrician practices (Vaccine Analyzer [VA] sample (0.43%; 1.13%). METHODS: The VA-sample was compared to the German population by age/gender. This comparison shows a disproportional distribution of the VA-sample. A disproportional sample distribution may result in biases of final estimates. Hence, we opted for a methodology to mitigate estimation biases that would result from a straight-forward projection methodology. The VA-sample was restricted to eligible practices. For the projection of the patient sample counts to the universe, a specific formula was used. The assumption is that the sampling ratio in terms of doses equals the sampling ratio in terms of patients. This assumption is theoretically valid as per medical recommendation one dose per patient shall be used. In summary, the estimation of total number of universe patients can be considered feasible from statistical point of view. RESULTS: The methodology to estimate total patient numbers is statistically valid and utilizes data sources in an efficient way. The assumption with regard to the conversion of patients into doses is in line with empirical findings. The stratified projection caters to disproportional distribution of VA-sample doctors. CONCLUSIONS: The usage of patient age information from the VA-sample is theoretically feasible. The empirical validation with independently sourced German Longitudial Prescription data of statutory insured patients shows differences, which is a certain weakness. As most vaccine-prescriptions are not patient-based the coverage is only 0.07% at paediatricians and 0.39% at GPs. However, VA-age distributions show an overall correlation of 80% which let the usage of VA-age distribution appears feasible. The suggested estimation method is methodologically sound and delivers results confirmed by observation, and statistically preferable to straightforward projection methods which are prone to bias.