Study population and setting
A cluster of SARS-CoV-2 occurred after a nursery serving children 1-2 years of age in Poland opened on May 18, 2020 after a nationwide lockdown. A staff member reported they had contact with a confirmed SARS-CoV-2 case on May 31, after which the nursery closed. Nursery staff, the children who attended the nursery during this time period, and family members of children were all tested (n=106). Investigators from the Medical University of Warsaw report the average number of children that attended the nursery daily during this time period, average time children and staff spent together, and secondary and tertiary cases that occurred from the presumed index staff member. Cases were confirmed through PCR testing.
Summary of Main Findings
Children were split into three groups (A, B, and C) with 2 caregivers per group and caregivers wore facemasks. A staff member of group A tested positive for SARS-CoV-2. Only family members of group A children were tested as there were no positive cases of children in groups B or C. Family members were not in contact with nursery workers for longer than 15 minutes, wore face masks, and did not interact with family members of different children at the facility. There was an average of 25 children who attended the nursery per day during the time period, and they spent at least 8 hours at the facility. There were 5 staff members, 3 children of the staff members, 1 spouses of the staff members, 8 children who attend the facility, and 12 family members (who had never entered the nursery) that were PCR positive for SARS-CoV-2, making the positivity rate of the cluster 27%.
The study includes comprehensive testing data for all of the staff and children who attended the nursery with additional testing data from family members among those who tested positive, thus it provides an accurate depiction of the positivity rate among those who attended the nursery during the time period.
Investigators only tested family members of group A as they assumed that any positive family members from children of other groups may not likely be attributable to the nursery. However, family members may also have contracted the infection directly from staff members or other family members of other children offsite from the facility, depending on how strict prevention protocols were followed. Additionally, there is no way to confirm that the staff member was the true index case as it is possible that there were asymptomatic cases of children or family members of children prior to the staff member.
This study shows that family members without contact inside the nursery, limited interaction with staff, and no interaction with other children at the facility were still at risk of becoming infected. Investigators report that the overall positivity rate in Poland was <1%, thus they are confident that results of secondary cases suggests that children may serve as mediators of transmission between schools and family members. This conclusion contradicts other reports suggesting that opening schools poses low risk of transmission to family members. Also, data suggest that transmission to children across groups did not occur as cases were limited to one of the three groups.
This review was posted on: 2 November 2020