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Everything women need to know about the AstraZeneca jab
In recent weeks, concerns have been raised about the safety of the AstraZeneca vaccine due to its potential link to blood clots. The news led to several European countries, including Norway, Austria, Iceland and Italy, to suspend the roll out of the vaccine. Germany has become the latest country to temporarily limit the use of the AstraZeneca jab for people below the age of 60, after the medicines regulator found 31 cases of a type of rare blood clot among nearly 2.7 million people who had received the vaccine in Germany. Most of these were women. However, experts around the globe have stated that the vaccine is safe for use and, that at this stage, there is no causal link between blood clots and the jab. Boris Johnson has supported their statements and received his first dose of the AstraZeneca vaccine this month. Why are there concerns? Many countries are concerned about the AstraZeneca vaccine’s potential link to blood clots. The first countries to raise concerns over the vaccine were Norway and Austria. A person in Austria died 10 days after they received the vaccination, after being diagnosed with blood clots. Another was hospitalised with pulmonary embolism (blockage in arteries in the lungs) after being vaccinated. However, Denmark became the first country to suspend the vaccine altogether, as someone died after they had received the jab. The latest country to suspend the roll out of the vaccine is Germany, pending a review by the European Medicines Agency (EMA). The German medicines regulator, the Paul Ehrlich Institute, has found 31 cases of cerebral sinus vein thrombosis (CSVT) – clots forming in veins that drain the brain – among people who received AstraZeneca in Germany. Almost all the cases are reportedly in younger and middle-aged women. What do experts say about the link between the vaccine and blood clots? Experts are in agreement that people should continue to receive the AstraZeneca vaccine. The EMA and the World Health Organisation (WHO) undertook a review of the evidence around blood clots and the AstraZeneca vaccine in March. Both organisations established that there is no evidence that there is a link between the vaccine and blood clots, and have actively encouraged other countries to continue using it. Dr Hans Kluge, WHO senior director, echoed this idea, saying that the benefits of the AstraZeneca vaccine “far outweigh the risks”. Experts have also pointed out that blood clots are fairly common: because the roll out of the vaccine is still in the early stages, it is tricky to distinguish between causal effect and coincidence. Professor Stephen Evans, of the London School of Hygiene and Tropical Medicine, said: “This is especially true when we know that Covid-19 disease is very strongly associated with blood clotting and there have been hundreds if not many thousands of deaths caused by blood clotting as a result of Covid-19.” Why are more women experiencing blood clots? Most of the blood clots that have been observed so far have been in women under the age of 65. Experts aren’t entirely sure why this is, but research into the topic is underway. One theory is that this demographic makes up most of the vaccinated population. Early clinical trials of the AstraZeneca vaccine included very few older recipients, so many countries decided to use the vaccine on people younger than 65. In practice, this meant that the vaccine was rolled out among priority groups, such as healthcare workers and teachers – professions which are mostly made up of women. Sara Viksmoen Watle, chief physician at the Norway Institute of Public Health, said that in Norway 78 per cent of the AstraZeneca doses went to women. In the UK, the vaccine was first given to the older population. In March, it was reported that the UK had five incidences of blood clots in people who have had the AstraZeneca vaccine, although the medicines regulator said that no causal link had been made with the jab. A study published this week by Swansea University found that no cases of blood clots have been found in more than 440,000 people who have been vaccinated against coronavirus in Wales. How does the risk of blood clots compare between the Pill and AstraZeneca? Some women have commented that the risk of blood clots from the AstraZeneca vaccine is lower than that of the contraceptive pill. A study published in The Lancet suggests that – excluding other factors such as weight and smoking habits – there is three times the risk of blood clots for women who take the contraceptive pill. The risk increases for pills that contain higher levels of oestrogen. According to the National Blood Clot Alliance, this equates to around one in 1,000 women per year. That’s why doctors don’t recommend that women take birth control pills if they have a history of blood clots, heart attacks or strokes. So how does this compare to the risk from the AstraZeneca vaccine? The risk of developing a blood clot from the contraceptive pill is significantly higher. According to figures from AstraZeneca, there have been 15 cases of deep vein thrombosis and 22 events of pulmonary embolism so far. Executives from the company say that this is similar to the rates of blood clots seen among other licensed vaccines. Is it safe for women to have the AstraZeneca vaccine? Yes. Simon Clarke, an associate professor in microbiology at the University of Reading, says no women should be concerned about receiving the AstraZeneca vaccine. “The numbers are so small that it is really impossible to point to any difference in the number between men and women as being significant. When you have small sample sizes, one or two increases in either direction can give you a false impression.” He adds that the risk of developing a blood clot from going on a plane, or taking the contraceptive pill, are currently far higher and the risk of having the vaccine remains “much less” than that of contracting the virus. Professor Beate Kampmann, of the London School of Hygiene and Tropical Medicine, agrees. She explains that the clots that have caused alarm in Germany are rare “manifestations of an auto-immune condition which affects activation of platelets in the blood”. These are the types of blood cells that make our blood clot if we have a cut, which can lead to clots in the brain. “At the moment, other than the age group concerned, which appears to be pre-menopausal, we don’t have detail on whether these women might have in any way been predisposed. Although this rare condition has now been added to the labelling of the AstraZeneca vaccine, it is obvious that it is extremely rare and that the benefits of the vaccine on a population level far outweigh the risks,” she says. “Covid itself can cause blood clots, and many more serious complications of covid continue to be prevented by the vaccine.” Worryingly through, these concerns are already starting to play out. This month, GPs in England warned that as many as one in 10 patients were either not showing up, asking to cancel or double-checking which jab they were getting before attending their appointment.