Scott Morrison has recommended people in Sydney’s lockdown try to get their second dose of AstraZeneca after eight weeks – instead of the recommended 12 – in a bid to give people faster protection against the Delta strain.
It has been hailed as a “great” reform by some, but one leading epidemiologist said he was “gobsmacked” at the change being announced in the middle of a press conference, warning constant “zig-zagging” on AstraZeneca could further damage public confidence in the safe and effective jab.
“I don’t think it should have been the Prime Minister announcing this. The chief medical officer wasn’t even there,” the Burnet Institute’s Professor Mike Toole said.
“There are advantages in what they’ve done, but the advice should come from the right people.”
Mr Morrison made his first public appearance in a week on Thursday afternoon, to announce details of the royal commission into veterans suicide, and outline new support for NSW’s spiralling COVID outbreak.
As part of a pledge to send 300,000 extra vaccine doses to Sydney, the PM also said he was “encouraging” people in the city’s south-west to get their second dose of AstraZeneca after eight weeks.
“That is consistent with medical advice – the TGA approval does sit, and ATAGI advice, on eight to 12 weeks,” Mr Morrison said.
Although the Therapeutic Goods Administration approved the two-dose vaccine to be given between four and 12 weeks apart, the Australian Technical Advisory Group on Immunisation “recommended” the second dose only after a 12-week gap.
“Given the risks to people of the outbreak in that [south-west] area, we believe it’s important they get that second dose of AstraZeneca as soon as possible. That is the community that is most at risk in these circumstances,” Mr Morrison said.
For over-70s in “the three local government areas most particularly affected”, he noted only about 50 per cent had a first dose.
Professor Toole said studies had shown taking the second dose earlier gave more protection faster, but the overall efficacy rate would end up lower than waiting the full 12 weeks.
That was consistent with Professor Sharon Lewin, director of the Doherty Institute, who told the Sydney Morning Herald she didn’t back shortening the interval, instead arguing people needed the “best possible mileage out of their vaccine”.
The Doherty Institute has been tasked by the federal government to set vaccination thresholds for reopening borders and removing COVID controls.
But some public health experts had called for the 12-week gap to be cut to eight weeks as the Delta outbreaks emerged.
Just a first dose of either the Pfizer or AstraZeneca vaccine is less effective against Delta than the original COVID strain, and epidemiologists said it was more important for people to have second doses and full protection.
Professor Toole was among them, and cautiously welcomed Thursday’s change.
However, he said the announcement was not ideal, coming after several changes to AstraZeneca – from initially making it available to all, to then restricting it to over-50s, then over-60s, and last week encouraging anyone under 40 to get it.
“People are a bit fed up with the zig-zagging on AstraZeneca,” he told The New Daily.
“If you were going to change the recommendations, then it first should be made by ATAGI and then communicated by the CMO.
“That’s how you do things and build confidence. I was a bit gobsmacked.”
TND contacted federal Health Minister Greg Hunt for comment, and the Department of Health for any official update from Australian Technical Advisory Group on Immunisation or TGA.
No reply was received by publication time.
Professor Toole said the more infectious Delta variant required as much protection as possible, noting a first dose of AstraZeneca only gave about 33 per cent protection against Delta.
However, he did stress the overall level of protection would be lower in someone who got their second dose earlier.
“The only big study comparing efficacy by period of dosage only compared 12 weeks versus six weeks, and there was quite a big difference. It was about 80 per cent at 12 weeks, and only 55 at less than six weeks,” he said.
“I’d guess it’s around 70 per cent for eight weeks.”
Professor Toole noted the British health system had already approved AstraZeneca to be given at eight-week intervals, due to Delta “running riot” there.
“Their logic is, if you get people their second dose quicker, you have a better chance of being fully protected against Delta,” he said.
University of NSW epidemiologist Mary-Louise McLaws shared similar thoughts.
“The English situation shows people with two doses were at much less risk than one dose. One dose may stop you from dying, may reduce your risk of hospitalisation, but may not protect you at all for symptomatic or asymptomatic infection,” she told the ABC.
Professor McLaws also noted shortening the dosing interval would reduce overall effectiveness, but said it was vital to get as much protection, as early as possible.
She suggested Australians who take that course, may require a third ‘booster’ shot.
“Once you get that second dose, your protection goes up to about 60 per cent. Not as good as before Delta circulating, but it is better than nothing, and certainly better than 33 per cent,” she said.
“Get those second doses, as suggested by the Prime Minister. It is a great idea.”