Is it ethical to continue with vaccine trials?

Since the COVID-19 pandemic began, there has been an incredible worldwide research effort into vaccines. At least 180 vaccines have seen the light of day, with at least 12 of them at the stage of phase 3 trials. But when a vaccine has been found to be safe and effective, should scientists feel it necessary to continue clinical trials? And should trials on other potential vaccines continue? These ethical questions are even more relevant since the announcement by Pfizer and Moderna that their vaccines work.

Clinical trials on the Pfizer and Moderna vaccines involved 43 000 and 30 000 participants respectively and proved effective at preventing COVID-19 symptoms to levels of 95% and 94,5%. Phase 3 trials are a particularly critical juncture from an ethical point of view since the effectiveness of the vaccine in protecting individuals has already been proven. Administering a placebo to a group of participants is therefore against their individual interests. Nevertheless, this step is important in order to collect sufficient data. Some people defend the notion that it is not ethical to continue clinical tests and research on other vaccines (which involve vaccinating participants with placebos) when these 2 vaccines have already proved their effectiveness.

Other people disagree. According to researchers at the National Institute of Health (NIH), USA, the obligations that scientists have towards their participants are not the same as those of a doctor. In a research programme, participants consent to accept certain risks with the aim of collecting data that will benefit the population at large. Research programmes are approved by an independent board which validates the calculation of benefits and risks and checks that all participants have clearly given their consent. Continuing clinical trials after having found a safe and effective vaccine may still be useful for verifying immune protection and undesirable side-effects in the long term.

What’s more, even if a vaccine proves to be safe and efficient, it may still be valuable to continue to develop other potential vaccines, which may turn out to be more effective in certain population groups, may bring longer-term immunity, or may be better in terms of logistics (stockage and cost for example). It should also be taken into account that to be able to supply an effective vaccine to different populations and for so many people, it may well be necessary to have several manufacturers producing vaccines using different technologies.

In all cases, researchers must keep participants informed of the results of their studies. Just because they have given their consent does not stop them leaving the trial. And if they leave, they are then informed as to whether they had been given the vaccine or a placebo.