Increased transmissibility of SARS-CoV-2 alpha variant (B.1.1.7) in children: three large primary school outbreaks revealed by whole genome sequencing in the Netherlands

Abstract

Background Variant of concern (VOC) SARS-CoV-2 alpha variant (B.1.1.7) was the dominant strain in the Netherlands between March 2021–June 2021. We describe three primary school outbreaks due to the alpha variant using whole genome sequencing with evidence of large-scale transmission among children, teachers and their household contacts. Method All outbreaks described were investigated by the South Limburg Public Health Service, the Netherlands. A case was defined as an individual with a real-time polymerase chain reaction test or antigen test positive for SARS-CoV-2. Whole genome sequencing was performed on random samples from at least one child and one teacher of each affected class. Results Peak attack rates in classes were 53%, 33% and 39%, respectively. Specific genotypes were identified for each school across a majority of affected classes. Attack rates were high among staff members, likely to promote staff-to-children transmission. Cases in some classes were limited to children, indicating child-to-child transmission. At 39%, the secondary attack rate (SAR) in household contacts of infected children was remarkably high, similar to SAR in household contacts of staff members (42%). SAR of household contacts of asymptomatic children was only 9%. Conclusion Our findings suggest increased transmissibility of the alpha variant in children compared to preceding non-VOC variants, consistent with a substantial rise in the incidence of cases observed in primary schools and children aged 5–12 since the alpha variant became dominant in March 2021. Lack of mandatory masking, insufficient ventilation and lack of physical distancing also probably contributed to the school outbreaks. The rise of the delta variant (B.1.617.2) since July 2021 which is estimated to be 55% more transmissible than the alpha variant, provides additional urgency to adequate infection prevention in school settings.

Household Secondary Attack Rates of SARS-CoV-2 by Variant and Vaccination Status

“…We identified 2097 records (1791 from PubMed, 306 from medRxiv, and 2 from reference lists of eligible articles) published between June 18, 2021, and March 8, 2022 (eFigure 1 in the Supplement). Fifty-eight new studies (eTable 2 in the Supplement) were combined with 77 studies from our previous review (see eTable 3 in the Supplement for references included from our previous review), with Figure 1 showing household SAR by study period, resulting in 135 total studies representing 1 375 806 contacts from 36 countries. Four of the new studies were preprints in our previous review that were subsequently published.…”

“…This reflects new variants and changing vaccination coverage. From highest to lowest, the overall household SARs were 42.7% (95% CI, 35.4%-50.4%) for Omicron (7 studies), 36.4% (95% CI, 33.4%-39.5%) for Alpha (11 studies), 29.7% (95% CI, 23.0%-37.3%) for Delta (16 studies), and 22.5% (95% CI, 18.6%-26.8%) for Beta (3 studies) (Figure 2). High heterogeneity was found among studies for Omicron ( I 2 = 98.2%; P < .001) and Delta ( I 2 = 99.1%; P < .001), moderate for Alpha ( I 2 = 59.6%; P < .001), and low for Beta ( I 2 = 2.6%; P = .79).…”

Can SARS‐CoV‐2 screening in oral biopsies aid epidemiological surveillance?

“…Interestingly, three of the nine positive cases were children. Gorgels et al 26 have recently reported three large primary school outbreaks in the Netherlands, suggesting increased transmissibility of the VOC Alpha among children aged 5–12. The higher prevalence of this variant in children was also observed in studies carried out in Argentina 27 and Turkey 28 …”

Testing the Efficacy of the ‘Corsi-Rosenthal’ Box Fan Filter in an Active Classroom Environment

“…We selected this building for testing as the classrooms most closely resembled the classrooms in the K-12 schools in the local districts based on size and ventilation. Classroom A had an approximate area and volume of 51m 2 and 125m 3 , respectively. Classroom B had an approximate area and volume of 96m 2 and 235m 3 , respectively.…”

“…The COVID-19 pandemic has proven to be a persistent problem that will require a multifaceted approach to solve 1 , particularly in the wake of the appearance of newer, more easily transmitted variants of the virus [2][3][4] . Indoor air quality is highly linked to COVID-19 mitigation as it is primarily spread through respiratory aerosols (particles) dispersed by infected individuals [5][6][7] .…”