The nation’s chief medical experts say a second dose of AstraZeneca is safe, reassuring Australians after the federal government’s abrupt move to raise the age limit for the shot to 60.

They have expressly ruled out giving people the option to “mix and match” one dose of AstraZeneca and a second dose of Pfizer, saying there is little evidence that it would be effective or safe, and could actually lead to more adverse symptoms.

“AstraZeneca remains a very effective vaccine,” chief medical officer Professor Paul Kelly said on Thursday after the federal government updated its advice following a handful of cases of blood clots in people who have received the vaccine.

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

The Australian Technical Advisory Group on Immunisation, the nation’s expert panel on vaccines, recommended on Thursday to raise the age cutoff for AstraZeneca to 60, from the current 50. It came a week after a second Australian, a 52-year-old woman, died following rare complications after receiving the AstraZeneca shot.

Photo: ATAGI

Australia has previously been delivering the Pfizer vaccine to those under 50, and AstraZeneca for over-50s. Many European nations took similar decisions, but set the AstraZeneca age at 60.

Australia’s current rate of blood clots developed after the AstraZeneca shot is 1.4 per 100,000 for those aged in their 60s, on latest Therapeutic Goods Administration advice. It has jumped to 2.7 per 100,000 for those in their 50s.

Professor Kelly said there had been 12 new cases of thrombosis with thrombocytopenia syndrome (TTS), a combination of blood clots and low platelets that is a rare side effect of the AstraZeneca shot.

Of those, seven were aged 50-59, which led to the updated guidelines released on Thursday. They include the death of a 52-year-old NSW woman last week, Australia’s second thought to be linked to the shot.

Under guidelines updated on Thursday, Pfizer will available for Australians under 60, and AstraZeneca for those who are older.

But Professor Kelly said the thousands of people in Australia who had had one dose of AstraZeneca should make sure they had a second.

“Anyone who has had a first dose of AstraZeneca without a problem should feel very confident to have their second dose and should keep that booking,” he said.

“We have not had a case of this particular syndrome in second doses in Australia.”

Of 15.7 million second doses of AstraZeneca administered in Britain, the condition has appeared just 23 times, or in just one in every 1.5 million shots – “way lower than the first dose”.

In Australia, 815,000 people aged 50-59 have had at least one shot of AstraZeneca. Another 25,000 have had a second dose.

“Remember this remains a very rare but sometimes serious event,” Professor Kelly said.

Health department secretary Professor Brendan Murphy said the move was a “highly precautionary approach given our good epidemiological situation”.

Chief Medical Officer, Professor Paul Kelly and Department of Health Secretary, Professor Brendan Murphy. Photo: AAP

Health Minister Greg Hunt said Australia’s vaccine rollout would be adjusted to meet the new advice. More than 1000 GPs will soon be able to offer the vaccine, as the government looks to “rapidly expand” access.

In a statement, AstraZeneca said its vaccine had “helped to save tens of thousands of lives” worldwide.

“AstraZeneca remains committed to supporting the rollout of the vaccination strategy in Australia and is confident that our vaccine has an important role in protecting Australians from the virus,” a spokesman said.

“Patient safety is AstraZeneca’s highest priority, and we continue to work closely with the TGA and other regulators around the world.”

AstraZeneca is the bedrock of Australia’s vaccine rollout, and the majority of doses that have been distributed. Melbourne’s CSL is producing more than one million doses of the vaccine a week.

Australia also has contracts for 40 million Pfizer doses.

The federal government has also contracted 10 million doses of Moderna and 51 million of Novavax. However, neither company has yet applied for TGA approval, and that will likely be months away.

Mr Hunt said he had reaffirmed forecasts from Pfizer to deliver another 32 million vaccine doses by the end of 2021. About 1.7 million doses will arrive in June, rising to 2.8 million doses in July.

“Are we on track to offer every Australian a vaccine who is eligible during the course of 2021? The answer remains and advice we
have is yes,” Mr Hunt said.

Professor Kelly said there had been some trials of “a mix-and-match approach” – giving a second dose of the Pfizer vaccine to someone who had had a first dose of AstraZeneca.

“Some countries have gone down that path, but there is very little evidence that it is either effective or safe,” he said.

“Some of the evidence we have so far is that you actually get more of those immunogenic, short-lived symptoms in the first 24 hours if you do AstraZeneca then Pfizer.”

Later, in Question Time, Opposition Leader Anthony Albanese slammed the government for a “failure to secure deals for the early supply of a diversity of vaccines”.

Shadow health minister Mark Butler said the change showed the government should have hedged more bets on supply.

“Scott Morrison placed too many eggs in the AstraZeneca basket. Australia does not have enough back up options and now we’re paying the price with not enough supply,” he said.

“Problems with specific vaccines were inevitable.”