Is the AstraZeneca Vaccine Safer than the Pill?

Despite announcing a restriction in its use to those over the age of 50, the Prime Minister yesterday continued to play down concerns over the safety of the AstraZeneca (AZ) vaccine.

Ten European countries have now paused or age-restricted its roll-out in response to cases of fatal brain clots. Morrison claimed that the AZ vaccine is “safer than the pill,” and went on to muddy the waters by pointing out that all vaccines, as well as ordinary medications like antibiotics, have side effects.

Morrison announced a restriction in the use of the AstraZeneca vaccine last night.

Is the AstraZeneca vaccine safer than the contraceptive pill?

The short answer is that no-one knows. First of all, the claim was made disingenuously, in that Morrison tried to compare the incidence of non-fatal blood clots to the severe and fatal reactions to the AZ vaccine that have been causing concern in Europe.

The contraceptive pill generates venous thromboembolism – a clot that becomes so big it blocks a vein – in 600 women out of every million every year. The concern with the AZ vaccine, on the other hand, is not just clotting in general, but cerebral sinus venous thrombosis (CSVT): clots in the brain that cause stroke.

CSVT occurs in about four women per million per year. For women taking the pill, the rate increases to 27 per million, or 1 in 37,000.

So what about AZ’s vaccine? The answer is not yet clear, because vaccination surveillance assessing the risks of the AZ vaccine are ongoing. Incidence of severe and fatal side effects post-AZ vaccine have varied significantly from country to country.

At one end of the spectrum, the UK has recorded 30 cases of CSVT and seven deaths, out of 18 million vaccine doses given, or roughly 1 in 600,000. Though this rate is much less than the contraceptive pill, the UK’s Joint Committee on Vaccination and Immunisation (JCVI) is recommending those aged 18-29 get other vaccines than AstraZeneca’s.

Next is Germany, which has recorded 31 cases of cerebral thrombosis in 2.7 million doses of the AstraZeneca vaccine, roughly one incident per 90,000 shots, including nine deaths. Germany has suspended the use of the AZ vaccine in those under 60.

At the top of the list thus far is Norway, where they have vaccinated 130,000 people with the AstraZeneca vaccine. This led to five CSVT cases and three deaths, that is, one fatality in 43,000.

The Norwegian case rates may be unusually high, or they may not be. If they are generalisable, vaccinating the 15 million Australian adults currently likely to receive the AstraZeneca vaccine would result in 348 deaths.

Some may say that it’s worth the risk to wipe out Covid-19, and that may be true if there weren’t other vaccines, like Novavax, that we could manufacture in Australia instead.

It would also be more comforting if AstraZeneca hadn’t been recently censured by the National Institute of Health for including “outdated information” in its trial results submission, and if the corporate and university-based teams hadn’t differed about a 2020 “dosing error” during testing.

Ultimately, the true risk of severe side effects from AstraZeneca may be outweighed by the benefits. A key element will be to determine whether women already taking the contraceptive pill are at even higher risk of CVST post-AZ vaccination.

That’s a discussion best had without disingenuous comparisons, and without sugar-coating data in the interests of “public sentiment.”

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