Decreased chlamydia notifications in six European Union/European Economic Area countries and England, 2024.

Over the last decade, bacterial sexually transmitted infection notifications have increased across the European Union/European Economic Area (EU/EEA) and England. However, six EU/EEA countries - Denmark, Finland, Ireland, the Netherlands, Norway and Sweden - and England, reported declines in chlamydia notifications from 2023 to 2024. To explore potential drivers of these decreases, the European Centre for Disease Prevention and Control, together with experts from the seven countries, analysed national surveillance data from 2015 to 2024 and contextualised findings with information on testing practices, policies and public health interventions. Chlamydia notifications in 2024 were compared with expected counts based on trends before the COVID-19 pandemic (2015-2019) using a negative binomial model. Across countries, decreases between 2023 and 2024 ranged from 13% to 19%, primarily affecting 15-24-year-olds. Case numbers fell below the 95% prediction interval in three countries. Five countries reported reduced testing volumes among young people, and all observed lower positivity rates. Some countries implemented online testing and targeted sexual health promotion campaigns. Although reduced testing, changes in behaviour during the COVID-19 pandemic and the risk profile of those accessing testing may have contributed to the declines, further investigation into underlying drivers is necessary to inform sexual health strategies in Europe.