We support Seroprevalence studies focussed on assessing how many Canadians have antibodies to SARS-CoV-2, the virus that causes COVID-19. People with antibodies have either likely a) had SARS-CoV-2 and have developed some form of immunity (see our Immune Mechanism area), what we call “infection-acquired immunity,” or b) have been vaccinated against COVID-19 and have what we call “vaccine-induced immunity”. Calculating seroprevalence continues to be highly important in the vaccine era. Vaccine rollout in the real world is not going to follow ‘textbook’ results, due to the rise of vaccine-resistant variants, the deviation of dosing schedules from what was used in clinical trials, and potential mix & matching of vaccines. In addition, we don’t yet know how long immunity lasts and therefore when a booster shot may be needed. Seroprevalence will therefore continue to be a useful broad mechanism to survey people’s immune responses at a macro, population level. We are managing our portfolio of supported seroprevalence studies for the greatest public health impact.