Case Study: How will we know if a COVID-19 vaccine works? Part I

For a COVID-19 vaccine to be successful, we need to know if it works. In the case of SARS-CoV-2, an efficacious vaccine may prevent infection, disease or transmission. Vaccine researchers may test and report efficacy against any of these endpoints.

The figure below shows how an efficacious COVID-19 vaccine may reduce:

• Likelihood of infection of an individual

• Severity of disease in an individual

• Degree of transmission within a population

Figure from Hodgson et al, 2020. Click here for an expandable PDF.

The most important endpoint for a vaccine is that it prevents severe disease and mortality as these place the biggest burden on healthcare. However, such a COVID-19 vaccine will only be effective if it reduces transmission, works in older adults and there is widespread access to and uptake of the vaccine.