Experts outline key challenges for assessing clinical efficacy of COVID-19 vaccines

Collaboration and standardised approaches for assessing different vaccine efficacy endpoints are key for meaningful comparison of different COVID-19 vaccine candidates to ensure that the most effective vaccines are deployed, say authors of an opinion piece based on a review of evidence, and published in The Lancet Infectious Diseases journal.

A candidate vaccine against SARS-CoV-2 might act against infection, disease, or transmission, and a vaccine capable of reducing any of these elements could contribute to control of the COVID-19 pandemic. In their Review, the authors highlight key challenges for assessing the efficacy of potential COVID-19 vaccines, to provide insight into the seemingly simple question, "Does this COVID-19 vaccine work?".

Author of the Review, Dr. Susanne Hodgson, University of Oxford, UK, said: "It is unlikely that we will see a single vaccine winner in the race against COVID-19. Different technologies will bring distinct advantages that are relevant in different situations, and additionally, there will probably be challenges with manufacturing and supplying a single vaccine at the scale required, at least initially. Taking a standardised approach to measuring the success of vaccines in clinical trials will be important for making meaningful comparisons, so that the most effective candidates can be taken forward for wider use."

Currently, there are 44 candidates in clinical assessment, with a further 154 in preclinical development, reflecting a range of vaccine technologies. The authors argue that to help compare efficacy between these and future candidates, it is important that standardised, quantifiable endpoints are applied to clinical trials of COVID-19 vaccines, and that their limitations and potential for bias are understood.

The authors also highlight a further challenge: evaluating the efficacy of candidate vaccines to protect against severe disease and death from SARS-COV-2 infection. They argue that long-term follow-up of recipients of candidate COVID-19 vaccines will be important, both to evaluate efficacy against severe disease and mortality, and to ensure the ongoing evaluation of vaccine safety.