The federal government’s vaccine committee is unlikely to change its advisory against people under 50 having the AstraZeneca vaccine due to the risk of a rare blood clotting condition after considering new European research that suggests it is twice as prevalent as previously reported.
But the study also forecasts the vaccine will still prevent many more deaths than it causes, even with relatively low levels of COVID-19 circulating in the community.
One of the first vials of the AstraZeneca vaccine manufactured at Sequiris/CSL in Melbourne.
New analysis from the European Medicines Agency puts the incidence of the clotting syndrome following the AstraZeneca vaccine at around 20 cases in every million for people in their 20s, 30s and 40s.
The rate halves to about 10 cases in every million for those in their 50s and 60s, and then halves again to about five cases in every million for those aged 70 and above.
The research has backed growing suspicion among doctors and scientists that the unusual side effect called thrombosis (blood clots) with thrombocytopenia (very low platelets) is comparatively much more common in younger people, who will not get the AstraZeneca vaccine in Australia.
Victoria’s Deputy Chief Health Officer Allen Cheng – who is also one of the most senior advisers to the federal government on immunisation – has not ruled out a change to Australia’s policy of continuing AstraZeneca vaccines for those aged 50 and over as a result of the new findings but said it was unlikely.
“Obviously we’re looking at all data as it comes in so if anything changes we might have to change our advice, but not at this stage,” said Professor Cheng, a co-chair of the Australian Technical Advisory Group on Immunisation, which is meeting on Wednesday.
The findings of the incidence of thrombosis with thrombocytopenia are about double the rate of the UK data Australian policymakers had previously relied on, which estimated a rate of about five per million for those in their 40s and 50s, and about 10 per million for those in their 20s and 30s.
Professor Cheng said incidence of cases reported from Europe was still a “pretty small number” and possibly a result of doctors getting better at detecting the condition, which has a fatality rate of about one in four cases.
“I’m sure very early on, before anyone realised what this was, people thought it was just an unusual clot … there may have been some that flew under the radar,” he said.
ATAGI issued an advisory in early April recommending people under 50 receive the Pfizer vaccine ahead of the AstraZeneca jab due to the risk of clots.
A number of leading experts in haematology and clotting conditions argue Australia’s policy of continuing AstraZeneca vaccines for people aged 50 and over strikes the right balance.
There has been one case of thrombosis with thrombocytopenia in a person aged over 50 in Australia to date – a Victorian man aged 80, who last week was in a stable condition in hospital – from more than 1 million vaccinations.
There have been another five cases, including a woman who died in NSW.
The head of the stroke unit at the Royal Adelaide Hospital, Tim Kleinig, said previous overseas data indicated the condition was most common in younger females.
Professor Kleinig said that was consistent not only in the AstraZeneca cases recorded to date, but also the Johnson & Johnson vaccine cases, where there had recently been 15 incidences of clotting reported, mostly in women aged under 50.
“It seems to me that 50 years of age is a very reasonable cut off,” he said. “As India shows us, to beat this disease we all have to get vaccinated, that’s the only way out.”
The European analysis weighs up the benefits of the AstraZeneca vaccine for different age groups, by looking at how many deaths it would prevent depending on the level of coronavirus circulating.
It forecast that in a medium infection rate situation, which Professor Cheng said was just close to the level reached during Victoria’s second wave, the vaccine would prevent 317 COVID-19 deaths among those aged 50 and over, compared to three cases of thrombosis with thrombocytopenia.
The benefit is also seen in a lower infection scenario, which Professor Cheng said was about twice the level of the Australian first wave, where 108 deaths are forecast to be prevented in older people compared to the three severe clotting cases.
However, the benefits are also skewed strongly to the elderly. For those in their 80s and above, 90 deaths are prevented at this lower level of infection, versus just one death in someone in their 50s, compared to one expected clotting case of someone in their 50s.
The forecasts are based on a four-month period, and assume a vaccine effectiveness of 80 per cent.
Professor Cheng said the key uncertainty for Australian advisers was now not so much the risk posed by the rare side effect, but what level of benefit the AstraZeneca jab would provide, as that would depend on the severity of any outbreaks that occurred in Australia in the coming year or so.
This new information on incidence of thrombosis with thrombocytopenia in different age groups will be used to update public advice to Australians.
Professor Paul Monagle, a paediatric haematologist at the University of Melbourne, said he hoped it would also help the public understand why countries had made different decisions on who gets the AstraZeneca vaccine based on the severity of outbreaks.
Professor Beng Chong, the director of haematology at NSW Health Pathology, said he believed younger people were more prone to the side effect because they had stronger immune systems.
Get our Coronavirus Update newsletter
Stay across the news you need to know related to the pandemic. Get it every Monday.
Most Viewed in National
From our partners
Source: Read Full Article