Pfizer no better than AstraZeneca long term, UK study finds

People who shunned AstraZeneca's Covid vaccine and risked infection by waiting for Pfizer may have made a mistake.

Over 60s holding out for the Pfizer Covid jab are in for a harsh reality check — it is no better than the AstraZeneca jab they could have got months ago in long-term efficacy.

A new study shows after four months, both vaccines provide similar protection against the virus.

The large UK study found the efficacy of the Pfizer jab fell by 22 per cent per month — from an original 84 per cent for adults overall — and after four and a half months it had around the same effectiveness against the Delta strain as AstraZeneca.

AstraZeneca’s efficacy began at 69 per cent for adults overall a fortnight after the second dose, before falling to 61 per cent after 90 days, the study by the University of Oxford, the UK Office for National Statistics and the UK Department for Health and Social Care (DHSC) found.

“Extrapolating declines beyond the observed follow-up, both vaccines would be equally effective against PCR-positives with (4.6 months) after the second dose and 116 days (3.8 months) against PCR-positives with symptoms,” the study found.

The study has not yet been peer reviewed by other experts or published in a medical journal, so the findings must be treated with caution.

AstraZeneca is as good as Pfizer long term, a new study shows. Picture iStock

Both vaccines were much more effective against Delta in younger people and provided stronger protection if the person had contracted Covid as well as being vaccinated, the study found.

Pfizer was 90 per cent effective against Delta in those aged 18-34 years versus 77 per cent for those aged 35-64 years.

AstraZeneca was 73 per cent effective in people aged 18-34 years and only 54 per cent effective in people aged 35-64 years.

Overall the third Australian vaccine option, Moderna, holds its efficacy for at least six months, other studies show.

University of Newcastle, Australia immunologist Professor Nathan Bartlett AstraZeneca said the UK study showed “AstraZeneca is an excellent vaccine. It’s always been comparable to the Pfizer vaccine in terms of protection against severe disease.”

“There is early evidence to suggest that maybe AstraZeneca does confer a little bit longer, or you know, the waning is a little less rapid than Pfizer but it’s not a huge difference and we don’t know whether or not that’s important. In the long run I think we’re still going to need boosters,” he said.

More important than protection against infection was the fact both vaccines were equally good at preventing hospitalisation and death, he said.

Professor Peter Collignon (PC), Professor of Infectious Diseases, Australian National University Medical School. Picture: Supplied

Australian National University infectious diseases expert Professor Peter Collignon said there had been vaccine snobbery in Australia with some people shunning the AstraZeneca jab.

“I haven’t said too much but I thought, won’t it be ironic if the AstraZeneca ended up giving you a better prediction than Pfizer over six to 12 months. We don’t know at the moment but it may actually,” he said.

More robust data comparing the effectiveness of the vaccines would become available by February or March next year, after the US and Europe have experienced more cases during their winter.

“We will then see what the effect is,” he said.

The US, UK and other countries including Israel have already approved booster doses for older people who had the Pfizer vaccine six to eight months after their first doses.

Australia’s government advisory body on vaccines is expected to rule on whether Australians need a booster dose in coming weeks.