Risk of Cardiac Death Tripled for Young Women Following AstraZeneca COVID-19 Vaccination: Study

A dose of the AstraZeneca COVID-19 vaccine in a file photograph. Louai Beshara/AFP via Getty Images

The risk of sudden cardiac death in young women more than tripled following an AstraZeneca COVID-19 shot, according to a study using England’s official data published on Monday.

Vahé Nafilyan, senior statistician at the Office for National Statistics (ONS), said researchers found “receiving a first dose of a non-mRNA vaccine was associated with an increased risk of cardiac death in young women.”

There was no evidence that the risk of death in young people increased following vaccination with mRNA shots, such as those produced by Pfizer-BioNTech and Moderna.

The ONS compared deaths of people aged between 12 and 29 that occurred within 12 weeks of COVID-19 vaccination—the so-called risk period—to those that occurred at all times after the risk period, to estimate the risk of death following vaccination.

After cross-referencing the deaths with records of COVID-19 vaccination and test results, the ONS said there had been “no significant increase in cardiac or all-cause mortality” within 12 weeks of receiving COVID-19 vaccines.

However, a breakdown of data showed that the risk of cardiac death among young women was three times higher in the 12 weeks following any dose of non-mRNA vaccination, compared with the longer-term risk.

When only the first dose was included, young women’s risk of cardiac death become 3.5 times higher within 12 weeks of vaccination.

But the ONS also noted that the subgroup who received non-mRNA vaccines “was more likely to be clinically vulnerable and may be at greater risk of adverse events following vaccination than the general population.”

It also said the absolute number of deaths was small.

“According to the statistical model, 11 out of the 15 cardiac deaths in young women that occurred within 12 weeks of a first dose of a non-mRNA vaccine were likely to be linked to the vaccine; this corresponds to 6 cardiac-related deaths per 100,000 females vaccinated with at least a first dose of a non-mRNA vaccine,” the ONS said.

Members of the public have the AstraZeneca COVID-19 vaccination at Fazl Mosque in Southfields as they host a drop in clinic, in London, on June 8, 2021. Dan Kitwood/Getty Images

The study also examined the effect of COVID-19 on young people, concluding that a positive test was associated with increased cardiac and all-cause mortality and that the risk was higher in those who were unvaccinated at the time of testing than in those who were vaccinated.

Noting the limitations of the method, the study said some deaths that occurred during the period may not have been registered by the cut-off date because deaths of young people and deaths that occurred soon after COVID-19 vaccination are more likely to be referred to the coroner and “registration delays can be substantial.”

Although the subgroup of deaths that occurred in hospitals were not subject to registration delays, sudden cardiac deaths mostly occur outside of hospitals and may not be captured in the data, the paper said.

Spike Protein May Be the Problem

Adam Finn, professor of paediatrics at the University of Bristol and a member of the UK’s Joint Committee on Vaccination and Immunisation, said the data generated “as many questions as answers.”

“The findings are somewhat unexpected, as concerns about rare cardiac side-effects—specifically myocarditis and pericarditis—have hitherto been particularly associated with mRNA vaccine second doses in males especially when the dose interval was short, whereas the signal reported here is primarily in non-mRNA first doses in females,” Finn said in a statement.

He said the overall data seems “reassuring,” and the increased mortality associated with a positive COVID-19 test result “raises the question whether the spike protein—which is expressed both during infection and following vaccination—is the cause.”

“The next and most pressing issue that needs to be addressed is to gather more detailed information on what the nature of the reported cardiac events actually was, as this would help us begin to understand what is really being seen in these figures and might help guide future policy and vaccine design,” he added.

Vials labelled "AstraZeneca, Pfizer-BioNTech, Johnson & Johnson, and Sputnik V COVID-19 vaccine" in this illustration picture taken on May 2, 2021. Dado Ruvic/Illustration/Reuters

UK and US Data

The ONS has long been criticised for not publishing raw data on mortality rates among the vaccinated and the unvaccinated in the same age groups, which mathematician Norman Fenton said would be most useful in evaluating COVID-19 vaccine efficacy.

In the new analysis, which was published earlier this month in Nature Communications, ONS researchers said they chose to use each participant as their own control group rather then directly comparing mortality rates among the vaccinated and the unvaccinated in the same age group. The vaccination campaign that targeted young people prioritised clinically vulnerable groups, who are probably more likely to die with or without vaccination.

A study from Florida last year (pdf) that used the same method found that mRNA vaccination may be driving the increased risk of cardiac-related death in males aged between 18 and 39, prompting the state to recommend against giving mRNA COVID-19 vaccines to the group.

ONS researchers said the Florida study introduced bias by combining deaths after first and second doses while extending follow-up beyond the interval between doses.

The make of vaccines and the intervals between doses in the UK and United States are also different.

Johnson & Johnson’s COVID-19 vaccine, which was not available in the UK, was the main non-mRNA vaccine in the United States.

In terms of mRNA vaccines, the UK used more Pfizer-BioNTech vaccines while the United States had more from Moderna. The waiting time between the two doses were also shorter then it was in the UK.