Canadian COVID-19 Antibody and Health Survey (CCAHS)

Detailed information for April 2022 to August 2022

Status:

Active

Frequency:

One Time

Record number:

5339

The Canadian COVID-19 Antibody and Health Survey (CCAHS), is collecting key information relevant to the COVID-19 pandemic to learn as much as possible about the virus, how it affects overall health, how it spreads, and whether Canadians are developing antibodies against it.

Data release - To be determined

Description

The Canadian COVID-19 Antibody and Health Survey will collect information in two parts. The first part is an electronic questionnaire about general health and exposure to COVID-19. The second part is two self administered tests; an at-home finger-prick blood test, and the second is a PCR saliva test, to be self-administered as soon as possible after the questionnaire, which is sent to a lab to determine the presence of COVID-19 antibodies.

The data will be used to:
- estimate how many Canadians test positive for antibodies against COVID-19. By using each participant's DBS samples combined with their survey responses, we will also have a better idea of how many Canadians have antibodies against COVID-19 due to infection, vaccination or both.
- to provide a platform to explore emerging public health issues;
- assist in the development of programs and services to respond to the needs of the current pandemic.
- to identify active COVID-19 infections in Canada.

Reference period: Varies according to the question (e.g. March 2020 until today, in the past 12 months, etc.).

Collection period: April 2022 - August 2022

Subjects

  • Diseases and health conditions
  • Health
  • Lifestyle and social conditions

Data sources and methodology

Target population

The target population for the survey is adults 18 years of age and older living in the 10 provinces.

The observed population excludes: persons living in the three territories; persons living on reserves and other Indigenous settlements in the provinces; full-time members of the Canadian Forces; the institutionalized population and residents of certain remote regions.

Instrument design

The content for the survey was developed by Statistics Canada's Centre for Population Health Data, with input from the COVID-19 Immunity Task Force (CITF) and in consultation with Health Canada and the Public Health Agency of Canada.

The survey takes place in two parts: an electronic questionnaire about general health and exposure to COVID-19. The second part is two self-administered tests. The first is an at-home finger-prick blood test and the second is a PCR saliva test. The samples are sent to a lab to determine the presence of COVID-19 antibodies and active COVID-19 infections.

Sampling

This is a sample survey with a cross-sectional design.

Frame
Dwelling Universe File (DUF) is used to select dwellings for persons 18 and over. Their contact information is then updated where possible using the 2021 Census database.

Sample design
It is a stratified random sample of dwellings, and age order selection will chose the respondent within the dwelling. The strata are based on the provinces and their census metropolitan area (CMA) regions within.

Sampling unit
The following sampling units are used in order to have accurate information on dwellings.

Residential Telephone Frame (RTF)
Dwelling Universe File (DUF)
Census 2021

Given the heterogeneity of COVID-19 in the population, particularly by geography, sub-provincial strata were created and the sample was allocated across these strata.

In the provinces, 27 strata were created from first subdividing each province into CMA and non-CMA areas. The CMAs of St. John's, Halifax, Saint John, Montréal, Québec, Toronto, Ottawa, Hamilton, Winnipeg, Regina, Saskatoon, Calgary, Edmonton and Vancouver form their own strata. From Ontario, Québec and British Columbia there are three additional strata of aggregated remaining CMA areas. Finally, there are 10 non-CMA regions, one for each province.

Stratification method
Typically, the population size of a stratum contributes to the sample size determination, where larger strata get more sample. This is then balanced by the need to ensure all strata receive sufficient sample to produce estimates. Increasing the sample in larger populations and increasing the sample in populations with more heterogeneity leads to more precise results at the national level. In this context, this means increasing the sample in large CMAs and strata with more COVID-19 confirmed cases leads to increased precision in the national estimates. Statistical sample allocation formulae were adapted to fit this specific situation, where the specific population size and proportion of confirmed COVID-19 cases for all strata were used in the allocation. Strata sample sizes were determined by a formula that favors larger population sizes and higher proportions of COVID-19 confirmed cases. The formula was then balanced to ensure sufficient sample was allocated to smaller strata with fewer cases. The results provide a sample allocation that will facilitate analysis for the hardest hit and larger strata with the added benefit of yielding more precise results nationally. Weighting that incorporates the sampling design will ensure that the final weighted sample is representative of the population.

Sampling and sub-sampling
Age-group definition:
The age groups defined in the proposal are quite broad being defined as 18-39, 40-59 and 60 and over, but analysis is not limited to these broad groups.

Within each household, one individual aged 18+ will be selected based on specific instructions within the letter they receive (or provided by the interviewer if they respond by phone). The instructions will use the age of household members to determine who is selected, and will vary from one household to another. For some households, the oldest member is selected, others the second oldest, or the youngest, etc. These letters are randomly assigned to the selected dwellings ensuring that the selected individual from within the dwelling is random. This method randomly selects individuals of all ages (18+) and given the proposed sample sizes, analysis can be conducted at much finer age groups for aggregated geographies. Weighting of the sample will also be performed for these finer age groups to ensure representativeness.

This comprehensive sample will provide nationally representative estimates as well as facilitating more granular estimation.

For those aged 18 and over, dwellings with a mailing address will be randomly selected, and one person from within the dwelling will be selected at random to participate. There will be strict instructions to ensure the selected individual does not choose a different person in the household.

A sample size of 100,000 people was selected for the survey, split between 3 approximately equal and overlapping waves of collection. Respondents of wave 1 of collection will receive a dried blood spot (DBS) antibody test, while respondents of wave 2 and 3 of collection (approximately 70,000 respondents) will receive a DBS antibody test and a PCR saliva test.

A response rate of 50% for the questionnaire, 30% for the DBS antibody test and 30% for the PCR saliva test is assumed. It is hypothesized that the prevalence of Canadians aged 18 years and older with antibodies against the SARS-CoV-2 virus during collection is approximately 90%. This represents persons that have previously had an infection from or have been vaccinated against SARS-CoV-2, and have antibodies against the virus. It is hypothesized that the prevalence of Canadians aged 18 years and older with an active SARS-CoV-2 infection during waves 2 and 3 of collection is less than 5%.

Data sources

Data collection for this reference period: 2022-04-01 to 2022-08-31

Responding to this survey is voluntary.

Data are collected directly from survey respondents.

1- Collection methods
A) Electronic questionnaire
The only contact with respondents is a letter sent through the mail with the DBS and PCR saliva test kits. The letter informs people living at the sampled address that a randomly selected person has been chosen to participate in the survey. On the letter there is a code which gives access to the online questionnaire. The electronic questionnaire takes on average 20 minutes to complete. Respondents are asked a series of questions covering a wide range of COVID-19 related questions as well as questions on chronic conditions, medication, health behaviour and interactions with the health care system.

B)
i. Dried blood spots (DBS) sample
The respondents are asked to provide a small blood sample (via finger prick) to be tested for COVID-19 antibodies. Respondents must prick their finger and place up to 5 blood spots on a test strip.
ii. A saliva test (polymerase chain reaction (PCR)) which you will administer to yourself as soon as possible after completing the electronic questionnaire and the finger prick. You will then return the saliva test using the enclosed prepaid package. The lab will analyse the sample to determine if there is an active SARS-CoV-2 infection.

All materials related to the survey (initial letter, questionnaire, DBS, PCR instructions, etc.) are available in both official languages.

2- Follow-up methods
A Statistics Canada interviewer may call, email or text the respondent to follow up if we do not receive the respondent's complete questionnaire. Afterword, a tracking system will be implemented in order to flag the DBS cards and PCR tests that have not be sent. Follow up calls will be done by CCAHS staff.

3- Languages offered
The questionnaire was developed in both official languages.

4- Average time to complete the survey
The electronic questionnaire takes on average 20 minutes to complete and the dry blood spot test takes approximately 10 minutes.

Coverage Error
The CCAHS covers the population aged 18 and older living in the 10 provinces Excluded from the survey's coverage are:
persons living in the three territories; persons living on reserves and other Indigenous settlements in the provinces; full-time members of the Canadian Forces; the institutionalized population and residents of certain remote regions. For the respondents 18 and over, this represents about 3% of the target population.

View the Questionnaire(s) and reporting guide(s) .

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