The development of COVID-19 vaccines has been a landmark breakthrough in managing the COVID-19 pandemic.
Most vaccinated individuals have either had mild to well-tolerated reactions to them. But is there a difference between men and women when it comes to the safety and effectiveness of COVID-19 vaccines?
An article published on 5th September by the University of Melbourne sought to answer this question. They referenced an international research paper that compared different published international studies to determine if people have responded differently to the various COVID-19 vaccines – depending on their sex.
The first were clinical trial reports published by regulatory bodies including the US Food and Drug Administration (FDA), the European Medicines Agency (EMA) and Health Canada.
The second group included five peer-reviewed studies conducted on the general population after the rollout of vaccines.
As quoted in the research paper “Historically, males and females have shown different reactions to vaccines of many kinds, which have become apparent with the arrival of COVID-19 vaccines in late-2020.”
“What we found was that 100 per cent of studies collected the information, but only 30 per cent reported on differences and side-effect profiles on men and women. Those that analysed the information, found there were differences.”
The findings
Vaccine efficacy was consistently found to be higher in males than females for the first shot of the vaccine, according to peer-reviewed studies.
It also looked at the key sex differences in historical vaccines like the 2009 H1N1 vaccine and influenza vaccines to give context for the results.
“International peer-reviewed studies that investigated the sex differences in effectiveness and safety within the general population also found that it was more common for females to experience negative side effects compared to males overall,” says Professor Cassandra Szoeke, Australian lead author.
This was particularly true for blood-clotting events which were more commonly reported among females who took the AstraZeneca and Janssen vaccines.
As mentioned in the article by the University of Melbourne “But there are no studies yet that assess the prevalence of blood-clotting events in young, vaccinated females compared to the general young, female population – or that take into account risk factors like hormonal treatment and immune disorders, which should also be investigated.”
A case for incorporating sex differences in trials
According to Professor Szoeke, sex differences should be reported not just in the distribution of adverse effects between men and women in the later phases of trials, but also in the study of vaccine dosage, pharmacokinetics and pharmacodynamics in earlier phases.
“This data is readily available. Given our findings that there were significant differences between sexes, it should be mandatory to routinely report by sex, so that each sex has the best-tailored information when they and their clinician are making decisions about their health.” she said.
“As we move toward more personalised medicine, this study highlights the importance of implementing regulatory mandates to report sex differences in the safety and effectiveness of new drugs and vaccines and for careful characterisation of sex-specific drug safety profiles during drug development.”
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