Is there a link between the AstraZeneca vaccine and blood clots?
Dr Khan explains why the European Medicines Agency has declared AstraZeneca’s vaccine to be ‘safe and effective’; examines why we must change our relationship with nature in light of the pandemic; and helps a patient with ‘long COVID’.
The global effort to roll out COVID vaccines suffered a blow this week when 11 European countries paused the use of the Oxford-AstraZeneca jab, after a number of people developed blood clots soon after receiving a dose. Outside of Europe, Indonesia also announced it would delay administering the vaccine while it awaits a review. The health authorities in these countries stated that the halting of the vaccine was merely a precautionary measure.
Four people developed blood clots a few days after having the Oxford-AstraZeneca vaccine in Norway in early March. Then, another person in Austria was admitted to hospital with a blood clot on the lung and died, 10 days after being vaccinated. Another death involving a blood clot has also been reported in Denmark.
On Thursday, after a few days of investigation, however, the European Medicines Agency stated that it was satisfied the vaccine is “safe and effective” and not, after all, linked to a higher risk of developing blood clots. It will continue to conduct research. Those countries which halted the use of the vaccine can now resume.
This should put the issue to rest, but the scare has caused understandable anxiety for those who have already had their Oxford-AstraZeneca vaccine, or who may be waiting for their second dose. So, what are blood clots and what causes them?
Blood should normally flow smoothly through blood vessels uninterrupted. Its main job is to carry nutrition and oxygen to our organs. To maintain this smooth flow of blood, it needs to move continuously and not stand still (which is why long periods of immobility can increase your risk). It also needs the chemicals or “factors” that control blood clotting inside us to stay in balance and for the inside of our blood vessels to stay smooth so the blood doesn’t catch on anything as it flows by, which is why inflammation inside of blood vessels caused by illnesses including COVID-19 can increase the risk of clots.
When any of these things upset the flow of blood it can clot, forming a clump of blood that has changed from a liquid to a gel-like or semi-solid state. This clot can then travel and block a blood vessel elsewhere, such as in the lungs, causing this area to be quickly starved of food and oxygen.
Blood clots happen in around one in 1,000 people each year. These tend to be people who are older, have certain cancers, are pregnant or spend long periods not moving about.
This is the number of clots that would occur in the general population who have not had any of the COVID vaccines. According to the European Medicines Agency, as of March 10, 37 cases of thromboembolic events (blood clots) had been reported among close to five million people vaccinated with the Oxford-AstraZeneca COVID-19 vaccine in the European Economic Area. That is significantly fewer than what should be expected from any general population, even without being vaccinated. This number would be higher if the Oxford vaccine promoted clot formation. It is actually significantly lower.
AstraZeneca said in a statement: “A careful review of all available safety data of more than 17 million people vaccinated in the European Union (EU) and UK with COVID-19 Vaccine AstraZeneca has shown no evidence of an increased risk of pulmonary embolism, deep vein thrombosis (DVT) or thrombocytopenia, in any defined age group, gender, batch or in any particular country.”
On Friday, however, medical researchers in Germany said they had discovered a link between the AstraZeneca vaccine and one particularly rare type of blood clot believed to have occurred in a “very small number” of people who have received the vaccine. A cerebral venous sinus thrombosis (CVST) is a clot in part of the vessels that allow blood to drain from the brain. The symptoms of this type of blood clot include headache, blurred vision and weakness of part of the face or limbs.
The incidence of this type of blood clot is three to four people per million in the general unvaccinated population and, even with the “very small number” of people in whom this has occurred after having the vaccine, there is no related increase in cases in the vaccinated groups.
We do know that catching COVID itself can increase your risk of developing blood clots because of the inflammation it causes in the body, especially inside the blood vessels through which blood flows.
Many patients who are treated for coronavirus in hospital are routinely put on blood-thinning medication to reduce their risk of developing clots. As a doctor, I would say it is safer to get the Oxford vaccine than to get COVID. Mama Khan (my mum) has had her first dose of the Oxford vaccine and will be due her second one soon. I will be more than happy to take her to her appointment.
Progress Report: We must change our relationship with the natural world
SARS-CoV-2, the virus which causes COVID-19 in humans, is thought to be a zoonotic virus (one passed from animals to humans) which came from a bat.
Zoonoses comprise a large percentage of all newly identified infectious diseases as well as many existing ones. Some diseases, such as HIV, began as a zoonosis but later mutated into human-only strains. Other zoonoses can cause recurring disease outbreaks, such as the Ebola virus and salmonella. During the past decade, bird flu was a notable zoonotic disease, with farmyard birds either culled or ordered to be kept indoors in many Western countries. Others, such as the novel coronavirus that causes COVID-19, have the potential to cause global pandemics.
Zoonotic diseases can pass to humans through domestic, farmed or wild animals. This can happen in several ways including eating wild animal meat, via insects which transmit diseases by biting humans, wild animal attacks (bites and scratches), and through coming into contact with animal faeces and urine.
“Wet markets” which trade in live or dead wild animals are particularly high risk as there are likely to be many micro-organisms living within wild animals that we simply are not aware of. The two largest wet markets in the world are in China and the United States.
As more wild spaces are commandeered for farmland, it is also much more likely that farm animals will come into contact with wild animals which have been forced into smaller and smaller living spaces. This increases the likelihood of micro-organisms that cause infections finding a route from wild animals to human consumption.
Following a month-long fact-finding mission in China, a World Health Organization (WHO) team investigating the origins of the COVID-19 pandemic concluded that the virus probably originated in bats and passed to people through an intermediate animal, either by one animal eating another, or by mixing bodily fluids through scratching or biting. Therefore, it is unlikely that a human being ate the bat which transmitted this virus.
Bats are an important ecological mammalian species that can be found on all continents except Antarctica. They are a known reservoir of a variety of coronaviruses which generally do not make them sick, but which may become dangerous to agricultural animals or humans.
The COVID-19 virus is not the first virus thought to have originated in bats. Middle Eastern respiratory syndrome (MERS), first identified in Saudi Arabia, has been traced back to bats, as has severe acute respiratory syndrome (SARS), which was first found in China. Both of these viruses are from the coronavirus family.
Research has shown that a coronavirus currently being studied in bats, known as RaTG13, cannot bind with cell receptors in humans. This means it would have to have jumped first to another animal and mutated to a point at which it could then bind to receptors on human cells. Research is continuing as to how this may have happened.
This where the plot thickens; an unassuming mammal called the pangolin, the most trafficked wild animal in the world, has been implicated as this intermediate animal. The pangolin is a small animal which resembles an anteater or aardvark.
As well as a long snout, it has large paws that allow it to dig away at soil so it can get to the insects it likes to eat. It is covered in large plate-like scales, save for its soft pink underbelly. Whenever it feels threatened, it curls itself into a ball and the scales act like protective armour. This is the perfect protection against a predator that wants to eat it, but sadly makes it easy picking for humans who want to poach it. They simply scoop it up and take it to what is most likely its death.
The pangolin’s scales, which are made from the same stuff as human nails and hair, are much sought after in the Far East for traditional medicinal purposes. Pangolin scales have also been used in the manufacture of luxury leather items in Western countries.
Studies have shown that coronaviruses similar to the one which caused the global pandemic have been found in pangolins, and more recently a research paper showed the spike protein found in a specific pangolin, the Guangdong pangolin, could bind to receptors on human cells.
However, this is when it starts to become a bit murky. There is currently no evidence that the RaTG13 coronavirus in bats can bind directly to the cells of a pangolin, so it may be this was not the route of transmission for either pangolins or humans, opening up the possibility of another intermediate animal.
Furthermore, we have yet to find conclusive evidence that a pangolin passed the virus to humans; all we do know is that there is the potential for it to have done so. The authors of the study hypothesise that the RaTG13 coronavirus in bats may have merged with another coronavirus which was then able to infect a yet-unidentified animal and then humans, or possibly that there is an unknown coronavirus in bats that was able to infect pangolins and subsequently humans.
More research is needed but one thing remains clear, it is our interference in the natural world that triggered this pandemic.
By tearing down wild spaces for agriculture, industry and human habitation, we are forcing wildlife into smaller and smaller spaces which then results in wild and domesticated species coming into contact with each other when they should not. If we continue to illegally traffic animals across the globe in inhumane conditions, putting them in cages alongside other species, we are only going to encourage cross-species infection further.
This pandemic should serve as a warning; we must show kindness and compassion to the living world. The dangers of not doing so will be far-reaching and will affect generations to come. Increasing the amount of space given to the natural world and improving biodiversity is likely to benefit not only the creatures we share the planet with, but also ourselves.
In the Doctor’s Surgery: Caring for patients with ‘long COVID’
Miss W* is a 29-year-old woman who has come to see me at my surgery. She has extreme fatigue, memory loss and unrelenting pain in most of her body. Less than eight months ago, she had been a fit, able-bodied person who went for long runs and enjoyed spending time with her young children. She was good at her job as a manager of a local shop.
Now, she is weak and worn out all the time. “The pain is just there every day,” she told me. “Just picking up my two-year-old daughter leaves me feeling exhausted.” She was trying hard not to cry.
When other shops and services were closed because of the lockdown last March, Miss W kept going to work, managing her team, and ensuring that people could continue to buy food and essential goods.
She had contracted COVID-19 at the height of the pandemic, suffering only relatively mild symptoms, and had stayed at home throughout, not needing medical intervention.
After the initial two weeks, she felt she was making a good recovery: her cough improved and she began to feel less tired. But three months later, just as she felt she was turning a corner, things suddenly went downhill. She found she could no longer concentrate on what was on the television, she was exhausted all the time and a dull ache set into her entire body. Initially she put it down to the recovery process, but then she began forgetting things and she could no longer walk with her children to the park without pain and exhaustion.
After examining her, I told her I thought she had “long COVID”, a condition that has yet to be formally defined but which involves not returning to a pre-COVID level of health and function even months after the initial infection. Common symptoms of long COVID include breathlessness, headaches, cough, fatigue, pins and needles, joint pain, depression and anxiety, earaches, feeling sick, diarrhoea, stomach aches, loss of appetite and cognitive impairment or “brain fog”. People suffering from chronic fatigue syndrome or myalgic encephalomyelitis (ME), both conditions thought to be triggered by viral disease, have symptoms that overlap with long COVID.
Having a formal diagnosis normally helps us determine a treatment plan to bring a patient out of the misery of their illness. Not so with long COVID. It is poorly understood, and we don’t know why some people, and not others, seem to suffer from it. It may be that there is an ongoing low level of inflammation in the body even after the virus has been cleared and some have speculated that it is a type of autoimmune response, where the immune system carries on reacting even after the virus has been cleared and starts to attack healthy human cells.
Whatever the reason, Miss W was looking to me to help her with her symptoms and to get her back to her old activities.
When there is no specific treatment for an illness, it can be a challenge to explain that to patients. They feel like they have been left to manage their condition on their own or, worse, failed by the medical profession altogether.
“This is a new condition,” I explained. “We do not know a lot about it, nor do we know the best way to treat it.”
Miss W looked as though any hope she may have had was now being cruelly snatched away.
“There are long COVID clinics being set up at the hospital and I think it would be best if I referred you there,” I told her. Indeed, our local hospital has set up a clinic to help these patients and is headed by the respiratory team who deal mainly with lung disease because many patients present with shortness of breath and a cough. Other specialists such as physiotherapists and occupational therapists are also involved in treatment.
She thanked me as she left, but I felt as though I had done very little for her. I knew whatever the hospital could offer her, there would be no quick fix and the focus would be on getting back to an acceptable quality of life rather than the life she was robbed of by COVID-19.
Many would say she is one of the lucky ones – she has had COVID-19 and survived. But at what cost? This virus has affected so many people in different ways and, as we feel our way out of this pandemic, we are likely to see the impact of these effects for years to come.
And Now, Some Good News: Vaccinations arrive in Palestine
On Wednesday, the COVAX programme, which has been set up to ensure equitable distribution of COVID vaccines to the world’s poorest countries, delivered a shipment of 60,000 vaccines to Palestine, one-third of which will go to the Gaza Strip.
Over the next year, COVAX aims to deliver enough vaccines to inoculate one million people living in the Palestinian Territories. Since the start of the pandemic, the West Bank, where 3.1 million Palestinians live, has reported 146,359 cases of COVID, with 1,667 deaths. The Gaza Strip, where two million people live, has reported at least 57,891 cases and 572 deaths.
Reader’s Question: How can I tell if I have hay fever or COVID-19?
The main symptoms of coronavirus are a high temperature, a new, continuous cough and the loss of your sense of smell and taste. Certainly, with hay fever you may get excess mucus production in the sinus area which can affect your smell and taste as well as excess tear fluid production in the eyes, but the vast majority of people with hay fever do not get a high temperature. If you are in doubt, it is always safer to take a COVID-19 test and find out for sure.
*Details have been changed to protect anonymity