How the ‘90 per cent effective’ coronavirus vaccine works

On Monday, drug companies Pfizer and BioNTech stunned the world by announcing they had developed a coronavirus vaccine that was more than 90 per cent effective.

Few scientists believed that such a level of protection, which would put it on a par with some childhood vaccines, would be possible so early in the race to beat Covid-19.

The stock market surged and experts around the world welcomed the news, which raised hopes that the beginning of the end was now in sight after a year-long struggle against the pandemic. But many said more information is needed.

Pfizer and BioNTech are yet to share their data in a peerreviewed journal. The trial is still under way and some have said that the vaccine’s efficacy could change over time.

Nevertheless, if the results hold up, experts said the vaccine could help “bend the curve of the outbreak”.

The vaccine has been developed using a process – mRNA technology – which has never been approved for human use. So how does it work?

The National explains.

How do mRNA vaccines differ from conventional ones?

All vaccines have the same goal – to trick the body into thinking it has had the virus.

Traditional vaccines essentially involve injecting people with a dead, weakened or fragmentary virus so the body makes antibodies against it, as it would for a natural infection. But the process behind mRNA vaccines is different.

The “m” stands for messenger. It harnesses human cells, turning them into miniature vaccine factories by delivering genetic instructions that prompt the body to produce virus proteins without exposing the body to the virus. When this happens, the immune system begins to build up antibodies.

What is the benefit of this approach?

Making vaccines can be slow. Flu vaccines, for instance, are still grown in chicken eggs. Vaccines are also developed from live viruses grown in labs.

Experts say mRNA vaccines can be designed by computer within hours, making them cheaper to produce than traditional vaccines. They can also be more easily produced.

“The advantage of RNA is that it takes you literally days to make a new vaccine,” Drew Weissman, an immunologist at the University of Pennsylvania and an expert on mRNA vaccines, was quoted as saying in the Smithsonian Magazine.

The concept was demonstrated in 1990, but the delivery often ended badly in animal tests, inducing severe inflammation in mice.

But scientists discovered how to dampen or remove this risk, paving the way for safe mRNA vaccines for humans.

Because the technology is fairly new and was until now untested, there was no rush to take a mRNA vaccine to the market. The pandemic provided a new impetus.

Are other mRNA vaccines in development?

Yes. A US company, Moderna, is developing one using the same process. Scientists will be watching keenly to see whether this version is as successful.

More than 240 vaccines against Covid-19 are in development worldwide. Most use a protein subunit.

A viral vector is the second most popular vaccine, followed by the mRNA or DNA method, each of which uses the same technique. About 50 of these are in development.

Other types of vaccine being explored include live attenuated virus, a weakened mutation of the original virus; inactivated virus, made by disabling the pathogen using radiation, chemicals or heat; a protein subunit, which contains one piece of a virus antigen that cannot replicate; and virus-like particles, which resemble the virus in structure but do not contain its genetic material.