Never before have candidate vaccines been developed from scratch, tested on animals and completed early stages of human clinical trials all under six months. This is an acid test for vaccine science and development and the outcomes will have far-reaching consequences either way.

With novel coronavirus continuing to spread across continents infecting over 14.7 million people and killing over 0.6 million so far, the race to find effective drugs to treat COVID-19 patients and vaccines to prevent infections has been progressing at a blistering pace.

Never before

While drugs that have been permitted for use under emergency use authorisation have all been repurposed to treat COVID-19 patients, never before have candidate vaccines been developed from scratch, tested on animals and completed early stages of human clinical trials all under six months. If normally candidate vaccines take at least a few years to reach the stage of clinical evaluation, some experts are “cautiously optimistic” that by the end of the year or early 2021 we might know if one or more vaccines are safe and effective, and vaccines might even become “available”.

Even in the case of the Ebola vaccine tested during the 2014 outbreak in Guinea, research and animal studies had been conducted prior to the outbreak. In the case of the H1N1 vaccine, the well-developed influenza-based technology enabled quick development but not before the pandemic peaked in the U.S and many European countries. But in the case of the coronavirus, 24 candidate vaccines are already in clinical evaluation and another 142 are in the preclinical evaluation stage.

With most countries managing to only flatten the curve and not totally stop the spread, the possibility of new surges cannot be dismissed. There is overwhelming evidence that protection and herd immunity against the virus can be achieved only through vaccination.

Trials show encouraging results

One candidate vaccine developed by China using a recombinant common cold virus (adenovirus) as a vector to ferry the genetic material of the coronavirus was on June 25 approved for use exclusively by the military for one year. The approval was based on limited safety and efficacy results from phase-1 and phase-2 trials; the phase-3 trial to test the efficacy and safety of the vaccine on a large number of participants is yet to begin.

As per preliminary results, the Oxford University vaccine, which too uses an adenovirus, has been found to be safe and immunogenic in a phase 1-2 trial. A phase-3 trial is currently under way.

A U.S.-based company along with NIAID has found its vaccine that uses messenger RNA platform to be safe and immunogenic in a phase-1 trial. The phase-2 trial of the vaccine is currently going on and a phase-3 trial is set to begin later this month.

Interim results show that another vaccine candidate using the messenger RNA platform is safe and immunogenic in a phase-1-2 trial. Two Indian companies too have begun human clinical trials. There is this cause for cheer.

Note of caution

However, a note of caution is also in order. Past experiences with vaccine development for two coronaviruses — 2002 SARS and MERS — have shown that vaccines can “exacerbate lung disease, either directly or as a result of antibody-dependent enhancement”. Thus, the compulsion to rigorously monitor safety profiles of candidate vaccines cannot be overemphasised.

Efforts to accelerate clinical trials should not rely on shortening the follow-up period or by-passing critical steps in clinical testing but put in place protocols that allow the trials to seamlessly graduate from one phase to another.

This is an acid test for vaccine science and development and the outcomes will have far-reaching consequences either way.

Published in The Hindu on July 22, 2020