Thus, when prevention and diagnostic protocols are put in place, schools are not a major vector of transmission of COVID-19 and do not cause a significant increase in secondary cases, confirms a study on thousands of students New Yorker published in the journal Pediatrics (New window)
New York City closed its schools last spring, but unlike several other U.S. cities, it reopened them on September 21 with strict measures.
From October to November, 288,199 young New Yorkers were in “face-to-face mode,” or a quarter of all students in New York schools. In December, while the number of cases rose, 164,000 students were still.
By comparing school and community infection rates, the authors believe that schools are not necessarily vectors of the epidemic, but rather reflect community transmission.
The infection rate for the school population was 341.2 cases per 100,000 population, compared to 528.9 cases per 100,000 population in the community. According to the analysis, between October and December, 0.4% of students who were in class were infected; then 0.67% in December.
The authors of the study believe that strict health measures, including the wearing of masks for all, contributed to this low rate of transmission.
From the start of the school year, there was a mandatory rapid test for all students and teachers at least once a month. In December, the frequency of drug tests increased to once a week. As soon as a case was diagnosed in a classroom, it was automatically closed for seven days.
Same story in Canada
Another study, this time in British Columbia (New window), where we analyzed the cases in the schools of this province, arrives at the same conclusions. In the fall, the infection rate in these schools was 55 per 10,000 residents, compared to 73 per 10,000 residents.
In addition, it was observed that of the approximately 700 cases detected in students and teachers, half of these infections had occurred at home and 88% of them had resulted in less than four secondary cases.
Among 251 cases analyzed, 170 of these infections occurred outside of school (63% at home, 10% due to social contact, 2.4% during a sports activity).
The authors of this study, which is to be peer-reviewed, claim that the infection rate in schools was lower than in the community and that infections did not not play a major role in the spread of SARS-CoV-2
.
A recent analysis by the National Institute of Public Health of Quebec (New window) abounds in the same direction. From August 23, 2020 to March 20, 2021, 48% of infected students (for whom an exposure environment has been identified) report having been exposed to the virus at home; 40% in their daycare or teaching environment; 15% during a visit to a private residence; and 10% in shops.
Home exposure has steadily increased, while school exposure began to decline in March, shortly after the masks were imposed in schools (January 18 for secondary, March 8 for primary).
In the United States, the Centers for Disease Control and Prevention (New window) (CDC) also indicate that the majority of outbreaks in schools are the result of infections imported from the community and that transmission between students is generally rare.
The CDC says transmission is higher among high school students, but these infections are caused more by social interactions outside of school.
Strict sanitary measures have helped
These two studies remind us that the imposition of health measures is essential to keep the transmission rate lower in schools.
Moreover, in order to allow a safe return to class, the World Health Organization (WHO) considers that it is necessary to keep a low level of transmission in the community and to adopt several health measures (limited cohorts, wearing of the mask for all, improve ventilation).
Canadian researchers compared cases of COVID-19 in schools in Montreal, Toronto and Calgary (New window) last fall. They noted that in Montreal, where masks were not yet compulsory for students, the transmission rate in schools was higher than in the community. According to Simona Bignami, the Montreal experience has shown that it is necessary to have a series of measures to be able to curb the spread.
And as the data from theINSPQ, the number of outbreaks in schools began to decline in late February, while the number of cases in the community skyrocketed.
One of the authors of the study comparing Montreal, Toronto and Calgary, Simona Bignami, does not believe that we should see large outbreaks in schools by the end of the school year. The children are more outside, the windows are open. Wearing a mask is always required
, says this demographer and professor at the University of Montreal. On the other hand, if deconfinement leads to an increase in cases, this could have repercussions on schools.
She also wonders what will happen when school starts in the fall. If the majority of 12 to 17 year olds have been vaccinated, what will happen to the younger ones? Will they have to continue to wear a mask at school?
I believe the government missed its chance this winter and spring to improve ventilation in schools and adopt rapid testing. It is sad
, says Dr. Bignami.
She believes the use of rapid tests will be even more important in the fall, especially if several testing centers close as adults are vaccinated. Where will parents go to get their children tested if they have symptoms?
, she said, deploring the fact that the Quebec government demonizes this type of tests while they are one tool among others
.
The Minister of Health, Christian Dubé, has often repeated that rapid tests are less reliable than regular laboratory tests and may leak cases of infection or incorrectly indicate that a person has COVID-19
. Quebec used about 100,000 tests out of the 4.6 million available.
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