Comparison of new and recurring post-acute infection syndrome - results from a German population-based cohort

New respiratory infections after or while experiencing post-acute infectious syndromes (PAIS) can lead to resurgence of symptoms. Data comparing symptoms, related impairment, and duration of first and recurring PAIS episodes are lacking. This cross-sectional study was conducted in September/October 2025 within a large population-based digital cohort in Germany (DigiHero, registered under DRKS00025600). We included data from 2,801 participants retrospectively reporting a respiratory infection between September 2024 and August 2025 with subsequent long-lasting symptoms ≥ 12 weeks after infection. We compared self-reported first and recurring PAIS episodes. Of detected PAIS cases, 57% (n = 1,609) were the first episode and 43% (n = 1,192) already experienced a PAIS episode in the past. While symptom patterns were broadly similar, those reporting recurring PAIS without full recovery from a previous episode (n = 308) displayed a higher number and longer duration of long-lasting symptoms and a higher level of impairment due to their symptoms compared to those with first PAIS episodes or recurring cases that were fully recovered at the time of the new infection (n = 303). Among participants with recurring PAIS who compared their most recent with their first episode, 43% reported similar impairment, while 32% reported greater and 26% lower impairment. While after the COVID-19 pandemic PAIS is still occurring, a substantial proportion of all PAIS cases in 2024/25 in the DigiHero cohort resulted from those with recurring PAIS. Symptom profiles were in general similar for first and recurring PAIS episodes. However, recurring cases exhibited greater impairment and longer symptom duration, when they did not fully recover from a preceding PAIS episode before the new infection.