Large-scale randomized testing and tracking of contacts over time, which would give a more complete picture of who is transmitting the virus and how, has not yet been conducted in schools. In July, in the journal Emerging Infective Diseases, researchers at the Korean Centers for Disease Control and Prevention published results of tracking more than 59,000 contacts of 5,706 coronavirus patients. It was found that children under 10 years of age transmitted the virus much less than children aged 10 to 19 years, the transmission rate of which is equivalent to the transmission rate in adults. But only 3 percent of the patients in this initial cohort were 19 years and younger, and the fact that they were tested probably means they showed symptoms. It is still unclear how asymptomatic children, who are difficult to identify, can spread the virus; it is also unclear whether there are differences in transmission between the ages of 10 and 19.
“A lot of the data we get from different sources is messy and doesn’t necessarily point in the same direction,” said Nicholas Davis, an epidemiologist at the London School of Hygiene and Tropical Medicine. He and his colleagues used a statistical method called the Bayesian inference to test several hypotheses about children and Kovid. It should be noted that children become infected but show no symptoms and that children are less susceptible to infection. Based on epidemiological data from China, Italy, Japan, Singapore, Canada and South Korea, the researchers concluded that both premises are likely to be true. Their findings, published in Nature Medicine in June, estimated that people under the age of 20 are about twice as likely to be infected as older people, and that only 21 percent of 10- to 19-year-olds become infected with the virus. They could not make clearer age distinctions and also say how likely it is that any children infect others.
None of these studies directly address the impact of school opening on the spread of Covid. In fact, when researchers from the Universities of Washington’s Department of Global Health and Epidemiology began compiling summaries of models from 15 other countries to which students returned, they found “very few” scientific publications on the subject and relied primarily on news. In almost all countries, they note, security measures have been taken in schools, including face masks and social distance. None of the countries (except Sweden, where many schools were open) resumed classes before the national level of infection dropped significantly; there is no evidence to suggest that schools will open in areas of the United States where the virus is on the rise. In Germany, where the infection rate was higher than in other European countries, the return of senior students was accompanied by an increase in infections among themselves, but not by staff, according to a preprint conducted by researchers at the University of Manchester and Public Health England.
In Israel, students and workers wore masks after schools reopened in early May. But after a few weeks, these rules were relaxed. Haaretz said the outbreaks began shortly after thousands of schools became infected, closing many again. There is “no clear cause and effect” between the removal of the masks and the outbreaks, says lead author Brandon Guthrie, but this is “indirect evidence” that they offer some protection in audiences. It also shows how unacceptable health care schools can be.