Saad Shakir writes:
Early results from clinical trials on vaccines for COVID-19 are encouraging. The effects of vaccines on antibody production are positive after 28 days of vaccination and likely for longer. We will wait to see when or if the favourable effects on biomarkers will persist for longer periods in larger clinical trials.
Given the success in lowering the incidence of COVID-19 infection in countries with advanced public health systems in Asia and Europe, it will be difficult to conduct randomised clinical trials (RCTs) with real outcomes as primary end points (such as occurrence of symptoms of COVID-19 infection or a positive antigen test). They will require very large sample sizes which may be prohibitive. Therefore, it is likely, in fact desirable from a public health perspective, that vaccines will be licensed on the basis of favourable biomarker results with limited clinical trial data. The uncertainty caused by the limited information at launch is only acceptable if a robust post-authorisation active surveillance system for both safety and efficacy is in place. The system must have the capability for early regular interim reporting for signals (both safety and efficacy) so that actions can be taken promptly when necessary to protect public health. In addition, participants in an active surveillance system will be representative of all vaccinees in the community including subgroups who are difficult to recruit in RCTs.
The benefit-risk balance of a vaccine is a continuum between pre-marketing clinical trials and post-authorisation studies, so any development programme and the evaluation of the marketing authorisation must take into account the capabilities of post-authorisation active surveillance to fill gaps in benefit-risk evaluation.