Novovax allows volunteers on placebo to get Covid-19 vaccine in trials

Even when other authorised vaccines are made available, allowing volunteers on placebo to cross over to the active vaccine offers them an incentive to continue with the trials.

American vaccine developer Novovax said on Monday that it planned to allow participants in its ongoing Covid-19 vaccine trials to receive an additional shot, Reuters reported. This will ensure that those who received placebo doses initially receive the actual vaccine now, and vice-versa. All the participants, however, will continue to be "blinded" so they do not know if they received the experimental vaccine or the placebo, the news agency added.

Vials labelled "COVID-19 Coronavirus Vaccine" and sryinge are seen in front of displayed Novavax logo in this illustration. (Reuters)

A 'placebo' vaccine has no therapeutic value, but can function as a control for vaccine testing, where researchers gauge the efficacy of the actual vaccine dose by observing the "expected" physiological response in patients, who have no idea if they treatment they just received was active or inactive. Placebo-controlled studies are thus most commonly used in "blinded" clinical trials, where such information about vaccine efficacy is consensually withheld from the participants to illicit an expected response.

Even when other authorised vaccines are made available, allowing volunteers on placebo to cross over to the active vaccine offers them an incentive to continue with the trials. Novovax plans to put this incentive to good use, planning to cross over participants in its ongoing large, late-stage study in the United States and Mexico, Reuters reported, adding that Novovax will read out initial clinical data during the second quarter.

"The crossover arms ensure that all participants have access to an active vaccine candidate while allowing Novavax to continue to monitor the safety and efficacy of our vaccine over the long term," Reuters quoted Filip Dubovsky, M.D., Chief Medical Officer at Novavax, as saying. "We are grateful to the volunteers who stepped forward to take part in our clinical trials, without whom we would be unable to develop, study and ultimately deliver what we hope will be a significant tool in the fight against Covid-19," he said.