What we knowabout the AstraZeneca vaccine

The AstraZeneca Covid-19 vaccine will be available as a ‘second option’ in New Zealand from November 26 – here’s the lowdown, writes HANNAH MARTIN.

On November 10, Director-General of Health Dr Ashley Bloomfield announced the Oxford University/AstraZeneca Covid19 vaccine would be available for those who did not want to have the Pfizer vaccine.

Anyone aged over 18 years will be able to access the AstraZeneca vaccine, not just thosewho have a specific medical reason or are covered by an employment mandate.

The vaccine is one of four purchase agreements the New Zealand government has with pharmaceutical companies, and the third Covid-19 vaccine provisionally approved by Medsafe (the country’s medicines safety authority), back in July.

The Government has agreements to buy up to 7.6 million doses – enough for 3.8 million people – of the AstraZeneca vaccine.

The first tranche of doses arrived this month and were scheduled to be available by the end of the month. But the vaccine will not be available at all vaccination centres or GP clinics.

So what do we know about the AstraZeneca Covid-19 vaccine, and how does it work?

It’s a two-dose, viral vector vaccine. Viral vector vaccines use a harmless virus (an adenovirus) to deliver a piece of code to our immune cells to mimic an infection. The vaccine introduces the code into the body, which instructs our cells to produce the spike protein on the surface. The immune system recognises the spike protein as foreign and mounts an immune response against it, preparing the body to fight against the SARS-CoV-2 virus and prevent Covid-19 in the future.

The Janssen vaccine, also approved in New Zealand, is another example of a viral vector vaccine. Unlike the Pfizer/BioNTech vaccine, which needs to be kept very cold, the AstraZeneca vaccine can be stored at normal fridge temperatures (2 degrees C to 8C) for up to six months.

It has an excellent record when it comes to safety and effectiveness.

A phase-three trial found the AstraZeneca vaccine to be 76 per cent effective at preventing Covid-19 and even better at preventing severe disease and hospitalisation following infection. Pfizer’s vaccinewas 95 per cent effective at preventing symptomatic laboratoryconfirmed infection with the SARS-CoV-2 virus in people 16 years and older.

A study of 19,000 people from Public Health England, published in July, found two doses of the AstraZeneca vaccine 74.5 percent effective at preventing symptomatic Alpha infections, and 67 per cent effective against the Delta variant.

A second PublicHealth England study, from September, found AstraZeneca’s level of protection against hospitalisation 20 weeks after vaccination was 77 per cent, contrasted with 92.7 per cent with Pfizer.

There have been reports of a very rare, serious side effect called thrombosis with thrombocytopenia syndrome (TTS) – a blood-clotting disorder – following vaccination with AstraZeneca.

In June, the Australian government updated guidance for its Covid-19 vaccine roll-out to recommend only those aged over 60 get the AstraZeneca shot, due to the elevated risk in those under 60. Occurrences are still very rare. As of November 14, Australia’s Therapeutic Goods Administration (TGA) reported 163 cases of TTS, out of approximately 13.4 million doses of AstraZeneca vaccine given to date.The administration says its analysis shows an occurrence rate of two cases for every 100,000 doses (0.002 per cent).

Nine deaths in Australia have been linked to the first dose of AstraZeneca vaccine – a rate of 1.3 deaths for every million doses.

The most common reactions reported following the AstraZeneca vaccine are headache, fever, muscle pain, fatigue and nausea, the TGA says.

Reports of Guillain-Barre syndrome, a rare immune system disorder that results in muscle weakness and pain, and paralysis inmore severe cases, are also being investigated by regulators. Most people fully recover from the syndrome.

These reports are also very rare: The European Medicines Agency said a total of 833 cases had been reported worldwide following AstraZeneca vaccination by July 31, while about 592 million doses had been given in a similar time period.

Reporting disclosure statement: Clinical staff at Medsafe reviewed this post before publication. It was also reviewed by The Whole Truth: Covid-19 Vaccination expert panel member Dr Dianne Sika-Paotonu, an immunologist and senior lecturer in pathology and molecular medicine at the University of Otago.