Is the AstraZeneca vaccine safe? Here’s what we know

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The changed health advice on who should get the AstraZeneca Covid vaccine has caused confusion and concern among many Australians.

Federal Health Minister Greg Hunt confirmed on Thursday that Pfizer would now be the preferred vaccine for those aged 50 to 59 years old, instead of AstraZeneca, amid concern about rare but serious blood clots.

Those aged over 60 years old are still recommended to get AstraZeneca.

The announcement has sparked concern among some over-60s about the safety of the vaccine, as well as speculation it could further delay Australia’s vaccine rollout.

The change followed a change in advice from the Australian Technical Advisory Group on Immunisation (ATAGI).

“The updated medical advice is made with an abundance of caution noting that the UK provides for AstraZeneca vaccines for those 40 and above, South Korea for 30 and above, and Germany has no restrictions,” Mr Hunt said in a statement.

Here’s what you need to know.

Why did the vaccine advice change?

The risk of blood clots among those who get the AstraZeneca vaccine is very small regardless of age group but it is higher among those younger than 60 years old.

The federal and state governments initially agreed to set the age cut-off at 50 years old based on advice from ATAGI, but decided to change this after a number of cases of blood-clotting thrombosis with thrombocytopenia syndrome (TTS).

In the week before the announcement, there were seven TTS cases among those aged 50-59, and this increased the risk for this age group to a rate of 2.7 per 200,000. Previously it was 1.9 per 100,000.

RELATED: How to talk to someone who is vaccine hesitant

A 52-year-old woman also died earlier this month from a blood clot likely linked to the AstraZeneca vaccine.

The death led to calls from experts including Melbourne University Associate Professor Margie Danchin, an expert in vaccine uptake, for a review to the age cut-off for the AstraZeneca.

However, the risk of dying from TTS after getting AstraZeneca is still very low. There have been two deaths from about four million shots.

As La Trobe University epidemiologist Associate Professor Hassan Vally highlighted in a piece for The Conversation, the chances of dying from TTS are about as likely as being struck by lightning.

RELATED: Desperate young people booking vaccinations

For those aged over 60, ATAGI still believes the benefit of vaccination outweighs the risk.

“AstraZeneca remains a very effective vaccine,” chief medical officer Professor Paul Kelly told reporters on Thursday.

“The benefit of AstraZeneca in the over-60s remains much higher than the risk of this particularly rare but sometimes serious syndrome.

“And so people over 60 should still be rolling up to their GP or wherever they are getting their AstraZeneca vaccine and get that first dose.”

The risk of developing TTS among older age groups ranges from 1.4 per 100,000 for those 60-69, to 1.9 for those older than 80.

However, for those who get Covid-19, the consequences can be serious.

For every 100 people aged 70-79 years that got Covid in 2020, around 38 were hospitalised, seven were admitted to an intensive care unit (ICU) and four died.

Some younger Australians have also indicated they would like to be given the chance to get the AstraZeneca vaccine despite the risks.

“I’m 35. Like many women under 40, I’d gladly take the AZ vaccine, and should be given the option to make my own informed choices about the vaccines I receive once eligible people over 50 have understandably made their own choice that they don’t want it,” Guardian Australia medical editor Melissa Davey tweeted.

It’s also worth noting that the cut-off age reflects the fact that there is very little Covid-19 circulating in Australia so there’s less risk of getting the virus. In places like the UK where the risk of contracting the virus is higher, authorities have recommended people aged 40 and over get AstraZeneca, due to the potential impacts of getting Covid.

Risks are lower for the second dose

Australians aged 50-59 who have had their first dose of the AstraZeneca vaccine are still being urged to get their second dose because the risk of getting blood clots is much lower after the second dose.

ATAGI noted that in the UK, there was an estimated rate of 1.5 cases of TTS per million second doses, compared to 14.2 cases per million for first doses.

“People of any age without contraindications who have had their first dose of Covid-19 vaccine AstraZeneca without any serious adverse events should receive the second dose,” ATAGI has advised.

RELATED: Tough decision older Australians face over vaccine

How much does it protect against Covid-19 and other variants?

Getting the second dose of the AstraZeneca vaccine is very important in ensuring a high level of protection, particularly against the more infectious Delta variant that is currently circulating in Australia.

Real world data from Public Health England published in a pre-print paper last week showed AstraZeneca was 92 per cent effective in preventing hospitalisation from those who got the Delta strain, once they had both doses.

It was also about 67 per cent effective in protecting against symptomatic infection from Delta two weeks after the second dose. This dropped to about 30 per cent if people only had one dose.

AstraZeneca is even more effective against the original Wuhan wild-type strain of the virus.

Results of its Phase III trials showed the vaccine was 76 per cent effective against symptomatic Covid-19 (for the original strain of the virus), as well as 100 per cent effective against severe or critical disease and hospitalisation.

Public Health England data showed AstraZeneca was also 74 per cent effective against the Alpha strain.

charis.chang@news.com.au | @charischang2



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