Abstract Background and objectives Healthcare professionals (HCP) have a key role in raising awareness and informing older adult patients about vaccines. However, HCPs are sometimes unaware of existing vaccines or have little knowledge on them. This study aimed to identify the information flows within HCP networks and to find out which HCPs play a key role in interprofessional information transfer. Methods An online questionnaire was distributed in Hungary (HU), Italy (IT), the Netherlands (NL) and France (FR) among HCPs, such as general practitioners (GP), medical specialists (MS), public health physicians (PHP), pharmacists, specialists elderly care (SEC) and nurses. The questionnaire included a case study in which a new vaccine for older adults was about to be made available. HCPs were asked whom they would contact for additional information and by whom they would be contacted on their turn, to reveal the information flow. Data were analyzed using social network analysis, comparing the results between countries. Results Preliminary results show the top three information providers. These were identical for NL and IT, with the MS being contacted by the highest number of different HCP-types, followed by the GP and PHP. FR and HU had GP ranked first and MS second. The PHP ranked also third in HU, but in FR it was the geriatrician instead. The main requesters of information were pharmacists (IT, HU), GPs (NL) and community nurses (FR). Hospital nurses (IT, FR), SEC (NL) and GPs (HU) ranked second on the number of HCP-types they would contact for information on a new vaccine. Conclusions In each country GPs and MS were the most important information providers in the HCP network when a new vaccine is introduced. Main information requesters varied per country and were pharmacists, GPs, nurses, and SEC. Thus, GPs were both main information providers and requesters (NL, HU). Key messages • Our study identified the HCP-(information)network regarding (new) vaccines for older adults. GPs and MS are the main providers of information, while pharmacists, nurses, and GPs are main requesters. • Identifying the HCPs in the information network makes it possible to specifically target key HCPs and to provide them with tailormade information on new vaccines.