Lots of pluses and few minuses as operation coronavirus fightback nears

As far as vaccine efficacy goes, it doesn’t get much better than ­Pfizer-BioNTech — the mRNA vaccine showed efficacy of 95 per cent in clinical trials, meaning it provided extraordinarily high protection against illness.

Five million Australian will be able to get the Pfizer vaccine. The first immunisations are due to take place from late February and will include 678,000 ­people, including some frontline healthcare workers, quarantine and border workers, aged and disability care staff and aged-care residents.

The next phase of vaccination will include 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 uses 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 that 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 the vaccine will be effective against the new, more transmissible strain of COVID-19 and other variants that may follow. If that proves not to be true, mRNA vaccines can be quickly adapted to combat new strains of SARS-CoV-2.

It’s not clear how long the immune response 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 five 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 already rolling out the Pfizer vaccine at pace is encouraging. Israel has 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.

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 — 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 but if the indications out of Israel prove true in the wider population who receive the Pfizer vaccine, the signs are good 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 herd immunity may have been achieved. However, Australia has been able to secure only 10 million doses of the vaccine. The federal government says it’s in constant discussions about securing more, but most Australians are likely to receive the AstraZeneca vaccine, which has the advantage of being produced onshore.

Both vaccines will work to prevent disease among those who contract COVID-19, which is the chief goal of the government.