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AstraZeneca vaccine risk to women higher than previously thought

A recent analysis that examined deaths in Britain, where AstraZeneca’s Covid vaccine was restricted in 2021 because of safety concerns, has found that young women receiving at least one dose of the jab might have been more likely to die of a heart problem in the 12 weeks after vaccination.

The release of the analysis of immunisation and death records in Britain carries a big caveat: Britain withdrew AstraZeneca’s vaccine for young people under 30 in April 2021, citing the risk of rare but dangerous blood clots.

By that time, the young women who were immunised would have been mainly healthcare workers or medically vulnerable people at high risk of Covid because of age, health or employment, all of whom were vaccinated first.

So the results of the study may not apply to the general population.

“It could be that the people who are clinically extremely vulnerable are more susceptible to side effects from vaccination,” said Vahé Nafilyan, a senior statistician for Britain’s Office for National Statistics and one of the lead researchers on the study, which was published in the journal Nature Communications.

The vaccine was never authorised for use in the United States, reports The New York Times. But more than 3bn doses of it had been delivered worldwide by November 2022. It is cleared for use in more than 170 countries, although in recent months, some have relied only on bivalent mRNA vaccines for the latest round of booster shots because of Omicron’s dominance.

In the latest analysis, the scientists found six cardiac-related deaths per 100 000 young women who received at least one dose of the vaccine in Britain. In these women, the cardiac-related death was 3.5 times more likely in the 12 weeks after vaccination than after the 12-week period. Clots that block blood flow can cause a heart attack or stroke.

The researchers did not find a significantly elevated risk of death in any other subgroup or with the Pfizer-BioNTech mRNA vaccine, which was also widely used in Britain. And the study did not prove that the vaccines caused the deaths.

The benefits of Covid vaccines still vastly outweigh the risks, and the incidence of harmful events after vaccination remains very low, the researchers and other experts emphasised.

In the analysis, Covid was associated with one additional death for every 12 000 unvaccinated young people and one additional death for every 56 000 vaccinated young people.

“When you look at vaccination side effects, I think it’s very important to also look at the benefits,” Nafilyan said.

The researchers linked immunisation records to deaths from any cause recorded in people ages 12 to 29. They looked at data starting on 8 December 2020, when the vaccines were rolled out in Britain.

The mortality data came from two independent sources: deaths registered by 8 June 2022, and hospital deaths by 31 March 2022.

The team found a very small increase in cardiac-related deaths in the 12 weeks after vaccination in young men after a second dose of an mRNA vaccine, but said that the finding was not statistically significant. Only young women – just more than 177 000 – who received at least one dose of AstraZeneca, had a higher risk of cardiac-related death.

The analysis does not conclusively link the vaccines to the deaths, experts cautioned.

“It’s enough to catch my interest and say we should study this more,” said Daniel Salmon, director of the Institute for Vaccine Safety at Johns Hopkins Bloomberg School of Public Health. But, “I wouldn’t come close to drawing any causal conclusions.”

“Overall it’s fairly reassuring, but it does bring up some vaccines and some populations that deserve further study,” he said.

Other studies have linked vaccine side effects to specific subgroups. Data from several countries link the mRNA Covid vaccines to an elevated risk of myocarditis and pericarditis – inflammation of the heart or its outer lining – particularly in males aged between 12 and 29.

MedicalBrief reported last week (23 March) that AstraZeneca is currently under legal fire from dozens of people over the rare condition (involving blood clots along with abnormally low platelet levels).

Lawyers have already sent the company pre-action protocol letters, step one in a legal claim on behalf of around 75 claimants. Some have lost relatives and some have survived with catastrophic injuries after blood clots, according to The BMJ.

Many millions have had the vaccine without suffering complications but in 2021 the Medicines and Healthcare Products Regulatory Agency confirmed a possible link between the vaccine – Vaxzevria – and the condition involving clots. Those taking legal action have been diagnosed with vaccine-induced thrombotic thrombocytopenia.

The vaccine was linked to the disorder within weeks of its introduction, not just in Britain but in other countries in Europe as well.

Although not approved in the US, the Food and Drug Administration (FDA) in December 2020 had authorised a similar vaccine made by Johnson & Johnson.

Then, in April 2021, the FDA called for a pause in use of the J&J vaccine, after reports of blood-clotting in six American women. The recommended pause was withdrawn 10 days later, and the vaccine’s label amended to warn about the risk.

A year later, the FDA again restricted the vaccine’s use, saying it should be offered only to people who could not or would not opt for one of the mRNA vaccines. By then, the agency had received reports of 60 cases of the clotting disorder and nine deaths, out of 18m doses administered.

“Fortunately, as more and more of these data are collected and become public, we can continue to rest assured that the rate of serious side effects, referred to as adverse events, is remarkably low for both types of vaccines,” said Dr Susan Cheng, a cardiologist and epidemiologist at the Smidt Heart Institute at Cedars Sinai in Los Angeles, of mRNA and non-mRNA vaccines.

“That said, while the rates of these adverse events remains extremely low,” she said, “they are important and they need to be counted and analysed so that we can understand them better.”

The vaccine was never used in South Africa either, although an initial delivery was made to this country.

When the doses arrived from India at the beginning of 2021, reported MedicalBrief at the time, they were found to have an April expiry date and not the normal six-month one. After India refused to exchange the vaccine or give a refund, the Health Department sold the consignment to the African Union (AU), resulting in mixed reaction from various quarters.

Additional ammunition from the Health Department in defending its decision to sell the jabs was that the vaccine “was found to have limited efficacy against mild and moderate disease caused by the Covid-19 variant dominant in the country”.

In a TimesLIVE report, Professor Linda-Gail Bekker, co-principal investigator on the J&J Covid-19 vaccine implementation study, had concurred, saying there was “no new data to support a roll-out of AstraZeneca in South Africa”.

“The problem is not that the data pushes you (not to use the vaccine). The problem is that we don’t have data to push us in a positive direction," she said.

However, in a conflicting opinion, Wits vaccinology expert Professor Shabir Madhi told the Sunday Times that “the lives of 18 000 to 22 000 elderly South Africans could have been saved” had the country not sold 1.5m doses of the vaccine to other African countries in March.

“Canadian data have since shown that even one AstraZeneca dose offers 80% protection against severe Covid disease and death….” he was quoted as saying at the time.

Study details

Risk of death following COVID-19 vaccination or positive SARS-CoV-2 test in young people in England

Vahé Nafilyan, Charlotte Bermingham, Isobel Ward, Jasper Morgan, Francesco Zaccardi, Kamlesh Khunti, Julie Stanborough, Amitava Banerjee & James Doidge.

Published in Nature on 27 March 2023


Several studies have reported associations between COVID-19 vaccination and risk of cardiac diseases, especially in young people; the impact on mortality, however, remains unclear. We use national, linked electronic health data in England to assess the impact of COVID-19 vaccination and positive SARS-CoV-2 tests on the risk of cardiac and all-cause mortality in young people (12 to 29 years) using a self-controlled case series design. Here, we show there is no significant increase in cardiac or all-cause mortality in the 12 weeks following COVID-19 vaccination compared to more than 12 weeks after any dose. However, we find an increase in cardiac death in women after a first dose of non mRNA vaccines. A positive SARS-CoV-2 test is associated with increased cardiac and all-cause mortality among people vaccinated or unvaccinated at time of testing.


Nature article – Risk of death following COVID-19 vaccination or positive SARS-CoV-2 test in young people in England (Open access)


The New York Times article – Risk of death following COVID-19 vaccination or positive SARS-CoV-2 test in young people in England (Restricted access)


See more from MedicalBrief archives:


AstraZeneca sued over jab side effects


Debate continues over SA’s ditching of the AstraZeneca vaccine


Mhize: Sale of Astra Zeneca vaccine to AU completed


Debate continues over SA’s ditching of the AstraZeneca vaccine


Sale of AstraZeneca vaccines ‘resulted in up to 22,000 deaths’ of SA elderly







South Africa’s AstraZeneca vaccine now on ‘half-price’ sale

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