CITF-funded researcher Dr. Kate Zinszer, from the Université de Montréal, and her EnCORE study team have released additional preliminary, non-peer reviewed results indicating a marked increase in the number of Montreal youth aged 2 to 17 with antibodies due to a SARS-CoV-2 infection in recent months. They found that 9.7% of participants had antibodies to SARS-CoV-2 between May and August 2021, whereas 5.8% had antibodies between October 2020 and March 2021. The parents of 86% of the participants reported their children over 12 were vaccinated or that they intended to have their child vaccinated against COVID-19 when vaccines are available.
Participants were recruited from schools and daycares in four areas of Montreal with distinct socioeconomic and population differences: Plateau Mont-Royal, Montreal North, West island, and Mercier-Hochelaga-Maisonneuve (HOMA).
- The average number of children and youth who had antibodies due to a SARS-CoV-2 infection between May and August 2021 was 9.7% (11.1% for female and 8.4% for male participants). This represented an increase from 5.8% between October 2020 and March 2021.
- Geographical differences in positive cases were noted, with the lowest seroprevalence recorded in West Island (6.1%), the highest socioeconomic area studied, and the highest seroprevalence in Montreal North (15.1%), the area with the lowest socioeconomic status.
- In an online questionnaire, most parents (86%) reported they have vaccinated or will vaccinate their child as soon as this option is available.
- The main reason stated for not wanting to vaccinate their child was that there is not enough information on safety.
The study also found that the antibodies due to a SARS-CoV-2 infection in children and youth wane: 5.3% of participants who had detectable antibodies at one point no longer had detectable antibodies a few weeks or months after infection. Although antibodies are not the only measure of protection against infection, this may suggest these children and adolescents no longer have enough protection to ward off reinfection.
The EnCORE cohort is comprised of 1,222 children (51% female and 49% male, sex determined at birth), aged 2 to 17,285 of whom are in daycare, 567 in elementary school, and 370 in high school in Montreal. Blood samples from 936 participants were collected via finger prick (dried blood spot) and analyzed for the presence of antibodies recognizing SARS-CoV-2.