The month of June saw many Canadians rolling up their sleeves for a COVID-19 vaccine. The latest results from the Canadian Blood Services’ serosurvey reflect this, with vaccine-induced seroprevalence soaring to 86% across Canada (excluding the Territories and Quebec), up from 60% the month prior. Most importantly, the gap in vaccine coverage among socioeconomic groups has narrowed considerably compared to previous months. And while the rate of infection-acquired seroprevalence remained low in June, a persistent increased risk is seen among youth 17-24 years old, racialized communities, and individuals living in lower-income neighbourhoods.

Key points:

  • In June 2021, seroprevalence due to SARS-CoV-2 infection:
    • rose to 4.5%, up from 4.0% in May and 3.2% in April 2021.
    • was 2X as high in racialized donors than in self-declared white donors, similar to the previous report.
    • was 1.6X higher in donors from neighbourhoods with lower socioeconomic status (based on postal codes) compared to donors living in more affluent neighbourhoods, similar to the previous report.
    • was highest in blood donors aged 17-24, particularly in the Prairie provinces.
  • In June 2021, seroprevalence acquired through vaccination:
    • climbed to 86.1%, up from 59.8% in May and 23.6% in April.
    • was similar among donors from different socioeconomic groups (including racialized groups and lower-income neighbourhoods).
    • was 1.7X higher in racialized Canadians in June compared to May 2021.

The latest CBS data included nearly 17,000 people who donated blood between June 14 and June 29, 2021, in all Canadian provinces, excluding Quebec. Overall, the proportion of Canadians with antibodies against SARS-CoV-2 was 90.8%, primarily acquired through vaccination.

Vaccine-induced immunity soars among all Canadians

The proportion of blood donors with antibodies to SARS-CoV-2 acquired through vaccination specifically climbed to 86.1%, a 1.4X increase over May 2021 (59.8%) and a 3.6X increase over April 2021 (23.6%). While previous reports revealed gaps in vaccine-induced seroprevalence among socioeconomic groups, the June 2021 report revealed that these gaps have mostly closed. The rate of vaccine-induced antibodies among blood donors who self-identified as white stood at 86.9%, similar to that observed in racialized groups (83.1%), which includes Indigenous, Asian, and other People of Colour. Indeed, vaccine-induced seroprevalence among racialized communities nearly doubled since May 2021. Likewise, donors living in lower-income neighbourhoods, as measured by the Material Deprivation Index based on postal codes, were almost as likely to have antibodies acquired through vaccination (86.0%) to those living in higher-income neighbourhoods (85.5%).   This represents a significant reduction in the gap in vaccine coverage identified in May that was 1.15%.

Infection rates low, but risk persists among some groups

Canada’s levels of seroprevalence due to a past SARS-CoV-2 infection remained low in June 2021, at 4.5%. It was slightly up from the two previous months: 4.0% in May and 3.2% in April. However, in line with previous surveys, the rate of seroprevalence due to past infection with SARS-CoV-2 in racialized donors (8.0%) was more than double that of donors who self-identified as white (3.7.%). Moreover, donors living in lower-income neighbourhoods were 1.6X more likely to have evidence of a past infection with SARS-CoV-2 (7.0%) than donors living in higher-income neighbourhoods (4.3%).

In June 2021, infection-acquired seroprevalence was highest in those aged 17 to 24 years (9.3%), compared to other age groups, an increase of 2.3% from May 2021 (7.0%). This was particularly apparent in the Prairies, where the seroprevalence due to infection in 17- to 24-year-olds was 17.5% in Alberta, 15.6% in Manitoba and 14.3% in Saskatchewan.   It is notable in this age group (17-24) that levels of vaccination-induced seroprevalence are the lowest compared to other age groups.