How close are we to the silver bullet?

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How close are we to the silver bullet?

Wednesday, 08 July 2020 | Sunit Mediratta

Science cannot be rushed and the development of a reliable vaccine or drug by any institution will need to follow the highest standards of rigour. That will take time

The world is constantly being fed  news and reports focussed on Covid-19-related matters. The most exciting among them is any news about the possible discovery of a wonder drug or a vaccine against Covid-19 that would help mankind get rid of this pandemic and solve all problems resulting from it.

People get excited as soon as a new drug development is announced and TV channels grab eyeballs by breaking news about newer vaccines having been developed by scientists from around the world. Let me reassure you that no drug or vaccine can be developed overnight. In fact it takes years of research and clinical trials before any new drug or vaccine can be made available for commercial use. Most people would wonder why. The answer lies in understanding how any vaccine discovery process works.

The first step is the exploratory stage, where the scientists identify natural or synthetic antigens that might help prevent or treat a disease. These antigens could include virus-like particles, weakened viruses or bacteria, weakened bacterial toxins. This stage alone usually takes at least two years but with Covid-19, scientists have a head start because this isn’t the first Coronavirus they have tried to make a vaccine for. Vaccine trials for Severe Acute Respiratory Syndrome (SARS)  and Middle East Respiratory Syndrome (MERS)  had already begun in 2003 and 2012 respectively but were abandoned when those outbreaks receded on their own. Then comes the pre-clinical stage where animal testing is undertaken using rats, rabbits or monkeys. Scientists may vaccinate the animals and then try to infect them with the target pathogen, to test the immune response of the candidate vaccine as well as its safety. These studies give an idea of the response they might expect in human bodies and help arrive at a safe starting dose as well as a safe method of administering the vaccine.

Many candidate vaccines never progress beyond this stage because they fail to produce the desired immune response. This process takes at least a year. On successful completion of animal trials, an institution, private sponsor or company puts up applications to regulatory authorities for approval of the investigational new drug. Human trials can only begin after such approvals are granted.

The vaccine now enters phase I of human trials, which may have a small group of 20 to 50 participants. Participants are injected with the vaccine to assess the type and extent of immune response in humans. A small minority of participants may be injected with the pathogen after they have been vaccinated.

Promising results in this phase allow the drug to enter into the Phase II of testing. Several hundred volunteers participate in Phase II testing. These are randomised trials and include a controlled group of people that are given the drug and a placebo group of people that are given saline or water.

The objectives of Phase II testing are to further evaluate the vaccine’s safety, immunogenicity, proposed doses, schedule of immunisations and method of delivery.

Successful Phase II candidate vaccines move on to larger trials or Phase III. This phase involves thousands of people and the experimental vaccine is tested against a placebo. These trials are randomised and double blind which means that neither the volunteer nor the health officials are aware of who received the vaccine and who got the placebo. To fully assess the protective efficacy and safety of a vaccine, this phase of testing usually requires hundreds of thousands of participants. The Salk polio vaccine was tested on over 1.3 million people. On successful completion of this phase the vaccine gets licenced for commercial production.

The World Health Organisation (WHO) recommends that if a vaccine contains genetically modified organisms (GMOs) an Environmental Risk Assessment should also be undertaken and approved by the appropriate agency.

In general, non vaccine drugs are developed, tested and regulated in a manner almost similar to vaccines except that the number of human subjects in vaccine trials is usually larger.

Scientists caution that less than 10 per cent of the drugs that enter clinical trials in the US are approved by the Food and Drug Administration. The rest fail because they are not effective or have too many side effects. Because of this high failure rate, we must have multiple potential vaccines to test.

To put things in perspective, the history of vaccine development worldwide is not encouraging. The record in the US for developing an entirely new vaccine is four years. Despite all the efforts under way to fast track administrative clearances, experts in the US believe that a vaccine against the Coronavirus could be developed in 12 to 18 months.

And beyond this point lie the challenges of production and distribution at scale. All vaccines require maintenance of the cold chain to preserve their efficacy. Setting up scaled production and distribution infrastructure will require collaboration between the public and private sectors which in turn will add to the time to market.

So one must not get too excited by the frequent breaking news on TV and our WhatsApp groups. Any claim of an instant breakthrough in Covid-19 care is a sham for sure. And any Government or organisation claiming that they would have a drug or vaccine ready in a matter of months should be taken to task for spreading false hope and making irresponsible claims. The truth is that science cannot be rushed and the development of a reliable and safe vaccine or drug by any institution, no matter where, will need to follow the highest standards of rigour, and that will take time. In the meantime, social distancing is the only protection you need from the pandemic. (The writer is a neurosurgeon at Apollo Hospital)


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