?There has been a lot of information published about the possibility of blood clots in persons taking the AstraZeneca vaccine. As the science behind vaccine use is moving rapidly so is the guidance provided to health care providers and vaccine administration personnel.
In the clinical trial program, there was no increased risk of blood clots in the population receiving the AstraZeneca vaccine compared to those on placebo. Overall the trials studied over 34,500 patients on vaccine and over 20,000 patients in the placebo group.
This is a sufficiently large enough trial size to discern a difference in blood clots in the body. If, however, a blood clot which occurs in the brain at a rate of one in 125,000 to one in 1 million people, the trial would not pick up the difference. This is the reason why all modern health authorities such as Health Canada have instituted a post marketing surveillance program to monitor potential side effects as they occur.
Recently a scientific institute that functions as an advisory body to the German Health Authority published the result of a study where it labelled the blood clots in the brain as Vaccine Induced Prothrombotic Induced Thrombosis (VIPIT). This is a new diagnosis, which means a small number of persons receiving the vaccine would develop a blood clot in the brain sometime between four and 16 days after vaccine administration.
The person could develop many symptoms, such as persistent headache, blurred vision, seizures and possibly chest pains with difficulty breathing or pain the legs or arms with swelling. In its study results, this institute explained that the population affected seemed to be predominantly women under the age of 55.
The authors explained that the process of developing these blood clots followed the similar pattern as a well-known blood clot process called heparin-induced thrombocytopenia, a treatable condition if diagnosed early.
This report is what led the Canadian National Advisory Committee on Immunizations (NACI) to advise the various public health units in Canada on March 29 to recommend limiting administration of the AstraZeneca vaccine to people over the age of 55. The committee outlined the information regarding VIPIT and the AstraZeneca vaccine. This guidance was sent to all public health units in Canada.
On April 2, the Ontario COVID-19 science advisory table, which advises physicians on how to treat patients with COVID-19, published a guidance for emergency room physicians on what to watch for in case of suspected blood clots with the AstraZeneca vaccine.
The guidance was specific for blood clots in the brain. It mentioned no increased risk of general blood clots in the body. The most important part of the guidance was how to treat patients with suspected VIPIT. There are at least three approved drugs that can be used to treat this condition along with a standard immunoglobulin treatment. In other words physicians are now being told how to treat these cases.
What does this mean to me? Currently it is estimated that there have been over 300,000 AstraZeneca vaccines doses administered in Canada and so far no cases of VIPIT have been reported. More importantly, physicians have been warned of this potential risk as well as how to treat it.
Given the guidance provided by NACI and the Ontario science table, the AstraZeneca vaccine only will be administered to people over 55 as there have not been any cases of VIPIT in this population in Europe and Canada with over 20 millions does administered to date.
In essence, since we are now starting to inoculate the over 70s Ontario, it is very unlikely that a VIPIT case will occur, but if it should, emergency room physicians have now been advised how to treat this rare potential condition.
What is also well-known is that the new virus variants are faster to infect and can result in more serious consequences to those persons it infects. We are also in the middle of a third wave in Ontario with a case increase of 30 per cent over the last seven days at the time of writing. The AstraZeneca vaccine has been shown to be effective at preventing hospitalization with the B.1.1.7 or U.K. variant.
It is estimated that should you become infected with COVID-19, there is a one in 100 risk of blood clots. These blood clots can have devastating effects in the long term and potentially lead to the need to use blood thinners for prolonged periods after they have dissipated.
This is the reason why Health Canada, the NACI and science table continue to advise that the benefits of the AstraZeneca vaccine still outweigh the risks. More importantly these scientific bodies are taking all the possible precautions to protect the population being vaccinated. You should find comfort in that and trust that they are acting in your best interest.