Two out of five Canadians were unaware that they had been infected with COVID-19 last summer, according to new data from Statistics Canada.
From Apr. 1 to Aug. 31, 2022, StatCan along with the Public Health Agency of Canada and Canada’s COVID-19 Immunity Task Force conducted a second Canadian COVID-19 Antibody and Health Survey (CCAHS-2) to better understand the spread of the SARS-CoV-2 virus, which causes COVID-19.
The survey involved self-reported information about past and current infections and dried blood spot (DBS) testing to detect antibodies against the virus.
“Since antibodies resulting specifically from an infection can be detected, the results of the CCAHS-2 will help to better understand the prevalence and characteristics of Canadian adults with infection-acquired antibodies, including the extent to which they were aware or suspected that they had the virus,” reads the study, which was released on Monday.
Last summer, over 47 per cent of Canadians surveyed had previously tested positive for the virus at least once, while 10.3 per cent with antibodies from infection suspected they had contracted the virus but never tested positive. Meanwhile, more than 41 per cent of Canadians with antibodies from a past infection never previously tested positive nor suspected an infection.
“Most people with antibodies from a past infection who had previously tested positive obtained their result from a RAT (59.8%), compared with 40.2% who received a positive test result from a polymerase chain reaction (PCR) test,” reads the study.
In addition, more than 98 per cent of Canadian adults surveyed had antibodies against COVID-19 between Apr. and Aug. 2022. These antibodies were acquired through vaccination, a previous infection or both.
Nearly 54 per cent of Canadian adults living in private dwellings had antibodies indicating a past infection, 20 times higher than the 2.6 per cent observed in the first survey conducted from Nov. 2020 to Apr. 2021.
The study says nearly 54 per cent of Canadians had antibodies from a past infection last summer but the actual proportion of those infected since the beginning of the pandemic “would likely be higher.”
“This is due, in part, to the fact that an antibody response to an infection may not always be detectable, especially among those who are vaccinated who may generate fewer antibodies following a subsequent infection. In addition, antibody levels can decrease over time,” the study says.
Among Canadians who reported that they had previously tested positive for the virus, over 88 per cent had antibodies from a past infection. Meanwhile, 56 per cent showed antibodies from a past infection despite never testing positive but suspecting an infection, and nearly 37 per cent who never tested positive nor suspected an infection showed the presence of infection-acquired antibodies.
Furthermore, 60.1 per cent of racialized, non-Indigenous Canadians had antibodies from infection compared with 51.8 per cent of non-racialized, non-Indigenous Canadians.
The study involved adults aged 18 and older living in the 10 provinces, and a sample of 105,998 people was selected for the survey.
