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Data from 10,000 OHS participants studied for vaccine effectiveness

Feb 8, 2022 // Study Updates

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Ontario Health Study investigators merited a $500,000 CIHR operating grant to relate COVID-19 antibody levels to vaccine effectiveness by looking at COVID-19 infection levels, hospitalization rates and deaths in vaccinated OHS participants. They will also assess how immune response to vaccination varies by:

  • Type of vaccine (AstraZeneca, Pfizer or Moderna) including mixed doses
  • Number of doses received
  • Time since last dose
  • Time between those doses
  • Factors such as the participants’ age, sex, genetic makeup, and the impact of certain pre-existing health conditions (including cancer, arthritis, lupus, diabetes, kidney and liver disease)
  • Whether vaccine effectiveness varies by viral variant (including Delta and Omicron)

“By studying how antibody levels change over time, we can assess the efficacy of different vaccines, and provide insights into the need, and timing, for future boosters,” said OHS Scientific Associate Dr. Victoria Kirsh.

“Also knowing more about how people’s genetic traits, age and health status can impact immune response will help policy makers tailor recommendations for who can most benefit from boosters, and when.”

From December 2020 to June 2021, the OHS invited select participants to complete an online questionnaire about vaccination, previous COVID-19 infection, and underlying medical conditions and medications taken. The antibody study included 10,569 participants (age 21 to 93), of whom 62% were women. Participants also used an at-home kit to provide a dried blood spot sample, which was tested for antibodies to SARS-CoV-2 (anti-spike IgG, anti-receptor binding domain of spike (RBD) IgG, and anti-nucleocapsid (N) IgG). Collection of second dried blood spot samples from these participants begins February 2022.

With participants’ prior consent, some of the previously collected blood samples will undergo DNA extraction and genotyping, as will some of the dried blood spot samples. Researchers will then link the questionnaire and genetic data to several administrative health databases to ascertain COVID-19 infections, hospitalizations, ICU admission and death.

Examining how differences in people’s genetic make-up may affect antibody levels is vital to understanding possible sources of vaccine failure, Dr. Kirsh noted. “If there are common genetic variants found to drive a compromised immune response, this would support the idea of more widespread use of booster shots down the road.”

Read more about the OHS COVID-19 Antibody Study. The principal investigators for this project are Dr. Victoria Kirsh, OHS Executive Scientific Director Dr. Philip Awadalla, and CanPath Scientific Coordinator Kimberly Skead. The funding was provided by the Canadian Institute for Health Research.

CanPath’s COVID-19 Antibody Study is funded by the Government of Canada, through Canada’s COVID-19 Immunity Task Force, and by the Canadian Institutes of Health Research.