The Public Health Agency of Canada regcognised in its April 2021 release of the Canada communicable disease report that protective immunity due to natural infection appears to last at least 6 months.

Read the full report at https://www.canada.ca/en/public-health/services/reports-publications/canada-communicable-disease-report-ccdr/monthly-issue/2021-47/issue-4-april-2021/post-covid-19-immunity.html.