Coronavirus: Why Pfizer is one of the best vaccines on the market

Pfizer vaccine, one of the best on the market, utilises new technology that induces the body to make coronavirus’s spike protein then mount an immune response against it.

A vial of the Pfizer-BioNTech COVID-19 vaccine. Picture: AFP.

The first Australians to be given a COVID-19 vaccine will be getting one of the best vaccines on the market.

The Pfizer-BioNTech vaccine showed efficacy of 95 per cent in clinical trials, meaning almost everyone who is immunised with it who may be unfortunate enough to catch COVID-19 will be protected from illness.

After the Therapeutic Goods Administration (TGA) this morning provisionally approve the Pfizer vaccine, five million Australian will be able to get the vaccine. The first immunisations are due to take place in late February or early March, and will include 678,000 people, including some frontline healthcare workers, quarantine and border workers, aged and disability care staff and aged care residents.

A nurse prepares the Pfizer/BioNtech COVID-19 vaccine prior to administration in Glasgow. Picture: AFP.

The next phase will include all elderly adults, other healthcare workers, Aboriginal and Torres Strait Islander people over 55, younger adults with certain health conditions, and critical and high risk workers in defence, police, fire and emergency services and meat processing.

The first vaccine approved by regulators anywhere in the world, the Pfizer vaccine utlises new technology that induces the body to make the coronavirus’s spike protein and then mount an immune response against it.

It’s an mRNA vaccine which delivers a minute amount of genetic material into the cells. In contrast to traditional protein-based vaccines, which deliver an immune system-stimulating foreign substance to the body in an injection, gene-based vaccines instruct the body itself to make a toxin — known as an antigen. The messenger-RNA carries instructions to the body to make a foreign substance — in this case the spike protein — which then gets exported from the cells. The body recognises this antigen as a foreign substance and mounts an immune response, producing antibodies and T-cells to fight the infection.

It’s believed that the vaccine will be effective against the new, more transmissible strain of COVID-19 and other variants that may follow. But if that proves not to be true, another advantage of mRNA vaccines is they could be quickly adapted to combating new strains of SARS-CoV-2.

Chief clinical officer John Corman MD at Virginia Mason administers a dose of the Pfizer COVID-19 vaccine at the Amazon Meeting Center in downtown Seattle. Picture: AFP.

It’s not clear how long the immune response that the Pfizer vaccine generates will last. As the Therapeutic Goods Administration points out in its Public Assessment Report for the vaccine, in animal studies, antibodies and T-cells in monkeys declined quickly over 5 weeks after the second dose of the vaccine, “raising concerns over long term immunity, which will be assessed by clinical studies according to the sponsor”.

Early data in countries that are already rolling out the Pfizer vaccine at pace is encouraging. Israel has already vaccinated more than a quarter of its population with the vaccine. Early data from the country shows a 60 per cent reduction in infections among those aged over 60 between 13 and 23 days after the first dose. And a small study in Israel has shown recipients of the jab developed up to 20 times more antibodies within a week of having the second dose of the jab – higher levels of antibodies than seen in those who had recovered from COVID-19.

What isn’t known yet about any vaccine is whether they will stop transmission of SARS-CoV-2. However, if the indications out of Israel prove to be true in the wider population who receive the Pfizer vaccine, the signs are good that it will have some effect on interrupting transmission of the virus. This is because higher antibody levels lead to a stronger immune response which could clear the virus before someone has a chance to spread it. Pfizer has not published any data on whether its vaccine affects spread of COVID-19.

If Australia had used the Pfizer vaccine to immunise the whole of its population, it’s possible that herd immunity may have been achieved. However, Australia has only been able to secure a total of 10 million doses of the vaccine. The Federal government says it’s in constant discussions about securing more, but this currently looks unlikely, meaning most Australians will receive the AstraZeneca vaccine, which has the advantage of being produced onshore.

In the end, both of the vaccines will work to prevent disease among those who contract COVID-19, which is the chief goal of the nation’s health chiefs, who believe that this protection will allow an easing of some of the restrictions that have characterised ordinary life already for the best part of a year.