Objective: To elucidate the impact of lack of Palivizumab administration during off-season RSV periods on the RSV-related hospitalization among 29-34 weeks of gestational age (wGA) preterm infants. We utilized the summer of 2021 off-season RSV surge during the COVID19 pandemic. Methods: This multi-center retrospective observational study was conducted in 11 medical centers across Israel. We included infants > 1 year-old hospitalized with RSV infection between November 2017-August 2021. Patients were categorized into an in-season admissions group (November-March) and off-season admissions group (April-October). The primary outcome was the proportion of RSV hospitalizations among 29-34wGA infants in relation to total RSV admissions during the same season. Secondary outcomes included clinical severity parameters. Results A total of 3,296 infants were admitted during the RSV season, and 1,044 during the off-season. The proportion of 29-34wGA preemies was significantly higher in the off-season group compared to the in-season group (7% vs 2.1%, p<0.001). In the off-season group, we observed a significantly higher proportion of Jewish individuals (80.1% vs. 59.2%, p=0.001) and higher socioeconomic status (55.1% vs. 45.1%, p<0.001) compared to the in-season group. In the multivariable logistic-regression model, off-season hospitalization odds for 29-34 wGA preemies were significantly higher (2.6-fold, 95% CI:1.8-3.9, p<0.001) compared to in-season, irrespective of demographic covariates. Similar clinical severity parameters was observed between the groups. Conclusions Our results revealed a significantly higher proportion of infants born at 29-34 wGA among those hospitalized during off-season periods compared to in-season periods. These findings highlight the importance of including 29-34 wGA infants into future RSV immunoprophylaxis recommendations.

Background: Previous studies described a higher prevalence of cardiovascular comorbidities during the winter season. Data regarding seasonal association of atrioventricular (AV) block are scarce. Methods: A retrospective cohort analysis of all patients admitted to a tertiary medical center with AV block requiring a permanent pacemaker (PPM) implantation between 2006-2017 was performed. In a time-series analysis, the seasonal incidence of PPM implementations due to AV block was assessed and adjusted for meteorological factors. The association between the weekly incidence of PPM implantations and the weekly rates of influenza as reported by the Israel Center of Disease Control (ICDC) were also assessed. Result: The study population included 759 patients. Mean age was 76.1 years and 55% were males. Most of the patients (34.1%) were admitted in the winter season. In multivariate analysis, there was a significantly higher incidence of PPM implantations among men during the winter season as compared to the fall season (Adjusted IRR [Incidence Rate-Ratio] 1.40, 95% CI 1.05;1.88; p<0.05), and a significant increase of 24% in the incidence of PPM implantations during the influenza season as compared to the rest of the year (Unadjusted IRR 1.24, 95% CI 0.99;1.53; p<0.05). Conclusion: In the present analysis the incidence of PPM implantations due to AV block was higher among men during the winter season and correlated with high influenza illness rates. Further prospective and larger studies are required to assess these findings.