Surveillance of severe acute respiratory infections (SARI) using ICD-10 codes from electronic health records (EHR) lacks consensus on optimal case-defining codes.

We determined codes that maximise sensitivity (Se) and positive predictive value (PPV) for SARI associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza virus and respiratory syncytial virus (RSV) in Denmark, Iceland, Malta, Norway and Spain.

We included hospitalisations from week 21/2021 to 39/2023, with ICD-10 diagnostic codes for respiratory disease (three-character codes J00–J99) or COVID-19 (U07.1, U07.2, country-specific codes for Denmark). We assessed Se and PPV of individual codes against laboratory results. Based on Se and PPV rank-sum, we selected the top 10 codes and combined them into 10 sets per pathogen. We identified sets that maximised the clinical utility index (CUI = Se × PPV), categorised as excellent (≥ 0.81), good (0.64–0.80), satisfactory (0.49–0.63) and poor (< 0.49).

We assessed 395,163 hospitalisations for SARI-SARS-CoV-2, 313,418 for SARI-influenza and 192,936 for SARI-RSV, all tested. For SARI-SARS-CoV-2, code U07.1 (B34.2A, B97.2A for Denmark) had excellent utility in Denmark, Malta, Norway, Spain (≥ 0.82), and good utility in Iceland (0.79). For SARI-influenza, J09, J10 and J11 performed excellently in Denmark, Norway, Spain (≥ 0.83), satisfactorily in Malta (0.52), and poorly in Iceland (0.43). For SARI-RSV, J12, J20 and J21 achieved highest CUI but had poor utility (0.17–0.34).

COVID-19- and influenza-specific three-character ICD-10 codes accurately identified SARI associated with SARS-CoV-2 and influenza virus. For SARI-RSV, four-character codes should be explored. We recommend context-specific assessments in countries adopting EHR-based surveillance.

Danish women vaccinated with the 4-valent human papillomavirus (HPV) vaccine (HPV types: 6/11/16/18) at age 14 in 2008 reached screening age in 2017, allowing assessment of long-term effects on prevalence, persistence and incidence of HPV infections.

To examine the HPV status of cervical samples over time among women vaccinated as girls.

Between February 2017 and February 2024, residual material from cytology-analysed samples collected through the ‘Trial23’ study, part of the national screening programme, was tested for HPV16/18 and non-vaccine high-risk (HR) HPV types. Prevalence in first, second and third samples, and persistence and incidence between samples were calculated.

Over 7 years, 8,659 women provided at least one sample, 5,835 at least two and 2,461 at least three. In 7,800 vaccinated women, HPV16/18 prevalence was 0.4% (95% confidence interval (CI): 0.2–0.5), 0.3% (95% CI: 0.1–0.4) and 0.2% (95% CI: 0.0–0.4) in three consecutive samples. Prevalence of non-vaccine HR HPV was 32% (95% CI: 31–33), 28% (95% CI: 27–29) and 31% (95% CI: 29–33). Persistence of HPV16/18 and non-vaccine HPV among vaccinated women was 40% and 53%. In adjusted analyses comparing vaccinated vs unvaccinated women, incidence was significantly lower for HPV16/18 (adjusted relative risk (aRR) < 0.10) while incidence of non-vaccine HR HPV types was higher (aRR: 1.66; 95% CI: 1.12–2.45). No significant difference was observed for persistence.

Our study provides real-world evidence of stable protection against HPV16/18 infections in women vaccinated as girls. Less intensive screening seems reasonable until women vaccinated with the 9-valent vaccine reach screening age, when screening should be reconsidered.