RESUMO
Background It is not known whether children born very preterm have an increased risk of severe symptoms following SARS-CoV-2 infection and whether a history of bronchopulmonary dysplasia (BPD) relates to more severe sympto-matology. We aimed to describe the prevalence of SARS-CoV-2 infection and the severity of symptoms in a sample of children with and without BPD born at a gestational age below 32 weeks, between 2006 and 2019 in the Zurich area, in comparison to their siblings born at term (≥ 37 weeks). Methods Parents were invited to complete an online survey for their preterm child as well as for a term sibling of similar age, between May 2021 and January 2022. The survey included questions about SARS-CoV-2 confirmed infec-tion, symptoms and treatment. Results The survey was completed for 654 preterm children (270 with prior BPD) and for 189 term children aged 2 to 15 years. 28 (7%) preterm children without BPD, 15 (6%) preterm children with BPD and 22 (12%) term chil-dren were infected by SARS-CoV-2. Out of the infected, the proportion of children with respiratory symptoms (cough, sore throat, shortness of breath) was higher in premature children with BPD (67%), than in preterm children without BPD (25%) and slightly higher than in those born at term (59%). In all groups, the majority of children had only mild symptoms. No child had to be hospitalised and only one preterm child with BPD required oxygen. Conclusion Very preterm children with BPD may be more likely to experience respir-atory symptoms following SARS-CoV-2 infection. However, similar to chil-dren born at term, most very preterm children with and without BPD de-veloped mild symptoms only.
RESUMO
Background Much remains unknown regarding the evolution of SARS-CoV-2 seroprev-alence in children, variability and clustering of seropositive children in schools and classes as only a few school-based cohort studies exist. Methods SARS-CoV-2 antibodies were measured in 1854 to 2585 primary and sec-ondary school children within 275-288 classes from 43-55 randomly se-lected schools in the canton of Zurich in June/July (R1) and October/No-vember 2020 (R2), in March/April (R3) and November/December 2021 (R4). Seroprevalence was estimated using Bayesian hierarchical model-ling. Variability in schools was expressed as maximum seroprevalence in a class minus minimum seroprevalence, and summarized as median (IQR). Results Median age at R1 was 11 yrs (min 6 to max 16), 47% of participants were male. At R4, 49% of participants at least 12 years old were vaccinated. Seroprevalence from R1 to R4 increased from 3% to 46.4% (95% credible interval [CrI] 42.6 to 50.9) including vaccinated children, or 24.7% (21.1 to 28.8) counting only recovered children. While in R1-R3 seropositivity rates were always higher in primary than secondary schools by 0.2-4%, at R4 much higher seropositivity rates were observed in secondary schools, 75.8% (69.6% to 82.4%), than in primary schools, 31.3% (27.1% to 36.1%). This difference was also the case if only recovered, unvaccinated children were considered. In R3 however chil-dren in primary school showed higher seroprevalence, 19.5% (16.0 to 23.7), than those in secondary school, 15.1% (10.7 to 19.6). Variability of class seroprevalence rates within schools increased steadily over time: At R2, median variability was 11% (IQR 7-17%), in R3, 24% (17-37%). At R4, median variability had increased to 40% (22-49%), and all but one of the primary schools had lower seropositivity than all the secondary schools Conclusion We observed a large increase in seroprevalence from R1 to R4, especially from R3 to R4 following introduction of the vaccine for children 12 yrs and older. Up to R3, primary school children had higher seroprevalence, how-ever at R4, secondary school children were more likely to be seropositive. This shift was in part due to introduction of the COVID-19 vaccine, but possibly also due to different behavior with more social contacts of older versus younger children outside school. Variability in seroprevalence among schools and classes was high and increased over time, even be-tween different classes in the same school.