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The Binax NOW Flu A+B enzyme immunochromatographic assay was compared to Real-Time PCR assay for 542 specimen from nasal-wash or nasopharyngeal swab collected during the pandemic of 2009. The overall sensitivity, specificity, positive predictive value, and negative predictive value of the assay were 44.6%, 95.8%, 73.5%, and 86.9%, respectively. The assay sensitivity shows mixed values decreasing significantly in infants and children age, which is linked with the quality and the way sample is collected.

•Co-circulation of different clades/subclades of influenza A viruses in 2018/2019 in the Region.•Most circulating A(H1N1)pdm09 viruses (6B.1A) carried S183P in hemagglutinin.•Genetically heterogeneous A(H3N2) viruses, with co-circulation of clades 3C.2a and 3C.3a.•Antigenically distinct A(H3N2) clade 3C.3a viruses were increasingly detected until 02/2019 and then decreased.•Co-circulation of genetically and antigenically diverse A(H3N2) strains challenges vaccine strain selection. The 2018/2019 influenza season in the WHO European Region was dominated by influenza A (H1N1)pdm09 and (H3N2) viruses, with very few influenza B viruses detected. Countries in the European Region reported virus characterization data to The European Surveillance System for weeks 40/2018 to 20/2019. These virus antigenic and genetic characterization and haemagglutinin (HA) sequence data were analysed to describe and assess circulating viruses relative to the 2018/2019 vaccine virus components for the northern hemisphere. Thirty countries reported 4776 viruses characterized genetically and 3311 viruses antigenically. All genetically characterized A(H1N1)pdm09 viruses fell in subclade 6B.1A, of which 90% carried the amino acid substitution S183P in the HA gene. Antigenic data indicated that circulating A(H1N1)pdm09 viruses were similar to the 2018/2019 vaccine virus. Genetic data showed that A(H3N2) viruses mostly fell in clade 3C.2a (75%) and 90% of which were subclade 3C.2a1b. A lower proportion fell in clade 3C.3a (23%) and were antigenically distinct from the vaccine virus. All B/Victoria viruses belonged to clade 1A; 30% carried a double amino acid deletion in HA and were genetically and antigenically similar to the vaccine virus component, while 55% carried a triple amino acid deletion or no deletion in HA; these were antigenically distinct from each other and from the vaccine component. All B/Yamagata viruses belonged to clade 3 and were antigenically similar to the virus component in the quadrivalent vaccine for 2018/2019. A simultaneous circulation of genetically and antigenically diverse A(H3N2) and B/Victoria viruses was observed and represented a challenge to vaccine strain selection.

Abstract Background Healthcare workers (HCWs) have experienced high rates of coronavirus disease 2019 (COVID-19) morbidity and mortality. We estimated COVID-19 2-dose primary series and monovalent booster vaccine effectiveness (VE) against symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron (BA.1 and BA.2) infection among HCWs in 3 Albanian hospitals during January–May 2022. Methods Study participants completed weekly symptom questionnaires, underwent polymerase chain reaction (PCR) testing when symptomatic, and provided quarterly blood samples for serology. We estimated VE using Cox regression models (1 – hazard ratio), with vaccination status as the time-varying exposure and unvaccinated HCWs as the reference group, adjusting for potential confounders: age, sex, prior SARS-CoV-2 infection (detected by PCR, rapid antigen test, or serology), and household size. Results At the start of the analysis period, 76% of 1462 HCWs had received a primary series, 10% had received a booster dose, and 9% were unvaccinated; 1307 (89%) HCWs had evidence of prior infection. Overall, 86% of primary series and 98% of booster doses received were BNT162b2. The median time interval from the second dose and the booster dose to the start of the analysis period was 289 (interquartile range [IQR], 210–292) days and 30 (IQR, 22–46) days, respectively. VE against symptomatic PCR-confirmed infection was 34% (95% confidence interval [CI], −36% to 68%) for the primary series and 88% (95% CI, 39%–98%) for the booster. Conclusions Among Albanian HCWs, most of whom had been previously infected, COVID-19 booster dose offered improved VE during a period of Omicron BA.1 and BA.2 circulation. Our findings support promoting booster dose uptake among Albanian HCWs, which, as of January 2023, was only 20%. Clinical Trials Registration. NCT04811391.

Background The emergence of SARS‐CoV‐2 in late 2019 saw the implementation of public health and social measures (PHSM) by countries across Europe to reduce its transmission and impact on populations. Consequently, countries reported changes in influenza circulation and extensive disruptions to routine surveillance systems. Methods We describe the epidemiology of influenza in Europe between Weeks 40/2020 and 39/2022 compared to the 2016/17 to 2019/20 seasons, to assess the impact of the COVID‐19 pandemic and PHSM on surveillance systems and influenza circulation. Results Low detections of influenza were observed through primary care sentinel sources during seasonal influenza periods (Week 40 to 20); 56 (of 39,457 specimens tested; < 1% positivity) in 2020/21 and 7261 (of 64,153 specimens tested; 11% positivity) detections in 2021/22 were observed, compared to an average of 18,383 (of 50,544 specimens tested; 36% positivity) detections in 2016/17 to 2019/20. Similarly, 11 (of 19,989 specimens tested; < 1% positivity) and 1488 (of 23,636 specimens tested; 6% positivity) detections were reported through SARI surveillance sources in 2020/21 and 2021/22, respectively, compared to an average of 2850 (of 10,389 specimens tested; 27% positivity) detections in 2016/17 to 2019/20. However, the 2021/22 interseasonal period saw unusual increases in influenza detections across surveillance site types when PHSM were easing. Conclusion In conclusion, findings suggest that the restriction and easing of PHSM measures were associated with variations in influenza detections. Our observations of out‐of‐season influenza activity highlight the importance of an integrated respiratory surveillance strategy to monitor circulating respiratory viruses throughout the year to inform optimal prevention and control strategies.

Abstract Background Recent studies explored which pathogens drive the global burden of pneumonia hospitalizations among young children. However, the etiology of broader acute lower respiratory tract infections (ALRIs) remains unclear. Methods Using a multicountry study (Albania, Jordan, Nicaragua, and the Philippines) of hospitalized infants and non-ill community controls between 2015 and 2017, we assessed the prevalence and severity of viral infections and coinfections. We also estimated the proportion of ALRI hospitalizations caused by 21 respiratory pathogens identified via multiplex real-time reverse transcription polymerase chain reaction with bayesian nested partially latent class models. Results An overall 3632 hospitalized infants and 1068 non-ill community controls participated in the study and had specimens tested. Among hospitalized infants, 1743 (48.0%) met the ALRI case definition for the etiology analysis. After accounting for the prevalence in non-ill controls, respiratory syncytial virus (RSV) was responsible for the largest proportion of ALRI hospitalizations, although the magnitude varied across sites—ranging from 65.2% (95% credible interval, 46.3%–79.6%) in Albania to 34.9% (95% credible interval, 20.0%–49.0%) in the Philippines. While the fraction of ALRI hospitalizations caused by RSV decreased as age increased, it remained the greatest driver. After RSV, rhinovirus/enterovirus (range, 13.4%–27.1%) and human metapneumovirus (range, 6.3%–12.0%) were the next-highest contributors to ALRI hospitalizations. Conclusions We observed substantial numbers of ALRI hospitalizations, with RSV as the largest source, particularly in infants aged <3 months. This underscores the potential for vaccines and long-lasting monoclonal antibodies on the horizon to reduce the burden of ALRI in infants worldwide.

Background Influenza virus infections are common and lead to substantial morbidity and mortality worldwide. We characterized the first eight influenza epidemics since the 2009 influenza pandemic by describing the distribution of viruses and epidemics temporally and geographically across the WHO European Region. Methods We retrospectively analyzed laboratory‐confirmed influenza detections in ambulatory patients from sentinel sites. Data were aggregated by reporting entity and season (weeks 40‐20) for 2010‐2011 to 2017‐2018. We explored geographical spread using correlation coefficients. Results There was variation in the regional influenza epidemics during the study period. Influenza A virus subtypes alternated in dominance, except for 2013‐2014 during which both cocirculated, and only one season (2017‐2018) was B virus dominant. The median start week for epidemics in the Region was week 50, the time to the peak ranged between four and 13 weeks, and the duration of the epidemic ranged between 19 and 25 weeks. There was evidence of a west‐to‐east spread across the Region during epidemics in 2010‐2011 (r = .365; P = .019), 2012‐2013 (r = .484; P = .001), 2014‐2015 (r = .423; P = .006), and 2017‐2018 (r = .566; P < .001) seasons. Variation in virus distribution and timing existed within reporting entities across seasons and across reporting entities for a given season. Conclusions Aggregated influenza detection data from sentinel surveillance sites by season between 2010 and 2018 have been presented for the European Region for the first time. Substantial diversity exists between influenza epidemics. These data can inform prevention and control efforts at national, sub‐national, and international levels. Aggregated, regional surveillance data from early affected reporting entities may provide an early warning function and be helpful for early season forecasting efforts.