Aug. 3 (UPI) -- Children at schools and day-care centers with strong COVID-19 infection prevention controls in place have low levels of virus transmission, according to a study published Monday by The Lancet Child & Adolescent Health.
In seven schools and daycare centers that underwent antibody screening, symptom surveys and testing, the child-to-child transmission rate was found to be 0.3%, while the child-to-staff transmission rate was 1%, the researchers said.
The rate of staff-to-child transmission was 1.5% and staff-to-staff was 4.4%, suggesting that children are less likely than adults to spread the virus, they said.
"It may be that higher rates of transmission occur in areas with higher levels of infection and where contact tracing and public health measures were not as rigorous as in Australia, where borders were closed and quarantine measures were strongly enforced," researcher Kristine Macartney said in a statement.
For their study, Macartney -- director of the National Center for Immunization Research and Surveillance at University of Sydney -- and her colleagues analyzed COVID-19 cases in 15 schools and 10 nurseries, or day-care centers, in the New South Wales state of Australia.
Australia, which had comparatively low COVID-19 incidence during the first wave of the epidemic, kept schools open during the first wave, with guidance in place for physical distancing and hygiene, researchers said.
The researchers looked at lab-confirmed COVID-19 cases in New South Wales and identified all staff members and children age 18 and under who attended school or day-care centers while infectious based on records in the state's centralized reporting system.
All patients or their guardians were interviewed at the time of diagnosis to track their attendance, as well as any contact with other people, the researchers said.
Close contacts were defined as those who had face-to-face interaction with an infected person for a minimum of 15 minutes, or 40 minutes in an indoor space, the researchers said.
Once identified, the contacts were monitored with regular phone calls, asked to quarantine for 14 days and be tested if they experienced symptoms of the virus, the researchers said.
Twelve children and 15 adults were found to have attended schools or day-care centers while infectious, researchers said. Contact tracing identified 1,448 close contacts, of whom 633 -- 44% -- were tested, they said.
Of those tested, 18 -- from three schools and one day-care center -- were found to have COVID-19 -- meaning that 1.2% of all 1,448 close contacts were positive -- the researchers said.
The outbreak at the day-care center involved transmission from one adult to six adults and seven children, suggesting that the transmission in schools and daycare centers stemmed from the staff rather than children, the researchers said.
The findings must be viewed "in the context" of the COVID-19 outbreak in New South Wales because transmission might be higher in other areas that did not practice the same types of public health measures as Australia, Macartney said.
For example, schools were closed temporarily for thorough cleaning if a pupil or staff member was found to be infected, she said.