Heatwave warnings in Europe: Research team calls for better evaluation of the effectiveness of health campaigns

For the study “Evidence-based communications for extreme heat and health”, now published in the renowned specialist journal Nature Health, the team led by lead author Dr Mirjam Jenny analysed eleven communication measures from Germany, France, Greece and the Netherlands, as well as initiatives by European and global institutions such as the World Health Organisation (WHO) and the World Meteorological Organisation (WMO). The study was based on three expert meetings, each attended by around 20 specialists from health authorities and research institutions in various European countries, which took place between May 2024 and June 2025. The study examined various communication initiatives, including websites, social media campaigns, leaflets, radio adverts, videos and warning notices on public transport. The campaigns are aimed at the general public as well as at particularly vulnerable groups, such as older people or those experiencing homelessness, and at visitors to major events such as the 2024 European Football Championship in Germany or the Olympic Games in Paris.

The study highlights the campaign by the French health authority, Santé publique France, as particularly successful. In contrast to traditional, risk-oriented messages, it adopts a positive, benefit-oriented approach and provides practical, everyday recommendations, such as cooling living spaces or improving sleep quality during heatwaves. A survey of more than 3,000 participants before and after the campaign showed that the positive framing generated greater engagement than traditional, threat-based communication. Almost half of those surveyed stated that they had implemented at least one recommended protective measure, whilst more than 70 per cent expressed their intention to do so in future.

The Netherlands is also setting a good example: the National Institute for Public Health and the Environment (RIVM) has carried out the first comprehensive evaluation of the Dutch Heat Action Plan for 2024 and 2025 in 20 years. The findings led to an adjustment of the communication strategy – moving away from purely self-protection information towards the message “Look out for one another when it’s hot”, which appeals in particular to carers and family members.

However, these two examples remain the exception. In most of the countries studied, communication measures are neither tested before their introduction nor evaluated after their implementation in terms of their impact on knowledge, risk perception or protective behaviour. Often, monitoring of success is limited to simple metrics such as website clicks. The study also shows that most campaigns continue to rely on fear-based, loss-oriented messages, whilst a differentiated approach to target groups – such as older people living alone, tourists or workers in particularly high-risk sectors – is rare.

Another key finding is that there has so far been little exchange between European countries regarding effective strategies, materials or evaluation methods. Existing European networks and institutions have so far been underutilised for this purpose. The researchers therefore advocate a more data-driven, theory-based approach to campaign development. Specifically, they recommend:

• the systematic pre-testing of communication materials prior to their publication,
• mandatory impact evaluation following roll-out, based on clear, verifiable objectives,
• the establishment of a Europe-wide database of evidence-based, previously evaluated materials for shared use,
• closer cooperation between European health authorities to pool resources and learn from one another.

The HEATCOM project, funded by the Federal Ministry of Health at the Institute for Planetary Health Behaviour at the University of Erfurt, which coordinated the expert meetings, already provides a data infrastructure for this purpose: in Germany, representative data on the population’s knowledge of heat, risk perception and protective behaviour are collected regularly. This data shows, for example, that around two-thirds of people in particularly vulnerable groups are completely unaware of their increased risk – a finding that underlines the urgency of more targeted communication.

Conclusion: In view of increasing heatwaves, it is not enough simply to disseminate warnings and safety advice – their effectiveness must also be demonstrated. The researchers are therefore calling on European health authorities to systematically test, evaluate and coordinate communication strategies across national borders in future in order to protect human lives.