Vaccine effectiveness against SARS-CoV-2 variants of concern in long-term care populations: a multi-province study

Viruses can mutate and change over time, which results in new versions or variants that behave differently from the strain they originated from. Some variants of COVID-19 can spread more easily, faster, may cause more severe outcomes. These are called Variants of Concern (VOC) and their presence in a vulnerable population, such as individuals living and working in long-term care (LTC) homes, may make it harder to slow the spread of COVID-19 and control outbreaks. Within a few short months, several VOCs have become the predominant strains transmitted in our communities across Canada. In this project, we are proposing to explore the humoral immunity in vaccinated LTC workers, residents, and family members/caregivers of LTC residents against emerging VOCs. We will assess their ability to neutralize VOCs or detect VOC receptor binding domains in a standard ELISA (enzyme-linked immunosorbent assay). We will also study the association between humoral response, socio-demographic and pre-existing health conditions, and the healthcare outcomes (including hospitalization, emergency room visits, and mortality) in this population. This project will be the largest prospective cohort following workers, residents and caregivers of residents in LTC homes across Canada to explore their immunity against VOCs. Our large sample size will support more complex analysis (including regression and prediction modelling) and sub-analysis (by disease groups) in this high-risk population. The findings will provide decision-makers with guidance regarding vaccine effectiveness in this high-risk and highly vulnerable population.