Medical Corner

A regular column written by Dr Kevin Gunning, a Luberon resident.

Kevin has gained a cult following on Luberon Life with his insightful and scientific take on current medical events. He talks sense, is practical and we listen to Kevin!

Risk and Coronavirus Vaccines

“Take calculated risks. That is quite different from being rash.” General George Patton.

It is a fact of life that we all take risks on a daily basis and much of the time hardly give them any thought. The tolerance of a given risk varies from individual to individual and depends on our evaluation of the risk and its consequences. Our acceptance of a risk is affected by previous experience, ideological and cultural factors and the severity of the consequences of the risk. However we are not always rational in our perception and evaluation of risks especially when the risk concerns ourselves and not others. There is a tendency to underestimate and accept risks when we feel we are in control such as driving a car, skiing or smoking. We often overestimate the odds of unlikely events and underestimate risky commonplace events. The uncertainty and continuous debate generated by the pandemic has sometimes led to a feeling of confusion and hesitancy in our ability to make decisions.

Set against the rising death toll and the second wave of the pandemic, the announcement of the Pfizer and Biotech vaccine against the SARS-CoV-2 in November 2020 was greeted with a sense of optimism and a light at the end of the tunnel. But from the outset there were concerns that the vaccines had been developed and approved too quickly to properly assess their risks. This was increased by the confusion over how the doses were administered in the trial of the AstraZeneca (AZ) vaccine. These concerns were greater in countries with a higher incidence of anti vaccination sentiment such as France and the USA. 

The efficient roll out of the vaccination campaigns in the UK and Israel showed that in a real life setting the vaccines appeared to be effective in reducing both the risk of catching Covid-19 and the severity of the disease. Case numbers and deaths from Covid fell markedly in both countries.

However reports from Norway and Germany in March of 30 cases of unusual “thromboembolic events” – blood clots, caused the temporary suspension of the use of the vaccine in several European countries including Denmark, Norway, Iceland Italy, Spain and France. After the results of an initial investigation vaccinations with the AZ vaccine resumed, but with restrictions as to which age groups it should be given to.

What do we know about these events and how worried should we be? 

First it has to be emphasised that all vaccines and medicines have some side effects. These side effects need to be continuously balanced against the expected benefits in preventing illness.

The European Medicines Agency (EMA) Risk Assessment Committee issued a report into its investigation of the cases on 7 April 2021. So far 34 million people have received the AZ vaccine in Europe and the UK and 222 cases of thrombosis, 18 of which were fatal have been reported to the EMA. The blood clots occurred in the brain (60%) and the abdomen and in arteries together with low levels of platelets (small blood cells that initiate clotting) and sometimes bleeding. These are very rare types of thrombosis. It is therefore difficult to give a precise figure of how often this type of event would be expected to occur spontaneously, but is around 2-5 per million of population per year. More of the cases have occurred in women under 60 years of age (but more young women have been given the AZ vaccine) and within two weeks of the first vaccination. No specific risk factors have been confirmed so far and there are no reports after the second vaccination.

Several theories have been put forward as to the explanation for the combination of blood clots and low platelets. It is similar to a clinical picture seen in patients who have an immune response to treatment with the anticoagulant drug heparin (heparin induced thrombocytopaenia HIT). Central venous thrombosis in the brain is also seen in Covid-19 infection and the same mechanism may be triggered by the vaccination. There has been a suggestion in a French media report that accidental intravenous rather than intramuscular injection could be the cause, but this does not sound very plausible to me.

Covid-19 is associated with a risk of hospitalisation and death. The reported combination of blood clots and low blood platelets is very rare, and the overall benefits of the vaccine in preventing Covid-19 outweigh the risks of side effects.

The EMA report therefore concludes that the vaccines are safe and effective.

It has requested further investigations and into the possible mechanisms are carried out.

Up to and including 31 March the MHRA in the UK has received 2 reports of blood clots (thromboembolism) reported with thrombocytopenia for the Pfizer/BioNTech vaccine. By this date, approximately 11 million first doses and 3.5 million second doses had been given. The EMA is also investigating a possible link between the Johnson & Johnson vaccine and four serious cases of unusual blood clots in the US, but the food and Drugs Drugs Administration (FDA) in the United States has not found any cause at present. 

Therefore the risk of serious harm from the vaccine is 4 in a million for a 55 year old and 11 in a million for a 25 year old compared with the risk of dying from coronavirus, which for a 55 year old is 800 in a million. To put this into perspective, the risk of dying due to accident or injury is 180 in a million, 23 million of dying in a car accident and 1 in a million of being hit by lightning. Women on the contraceptive pill have a risk of blood clots of around 300-900 per million.

If there was a delay in the vaccination campaign by a week 16,000 people might catch the virus and if they were over 60 years, then one would expect 300 to die, far greater than the number of deaths from the thromboses. For younger patients the benefits of the vaccine are not so clear as the number of fatalities from Covid would be lower.

As a precaution, the EMU and the MHRA recommend administration of the AZ vaccine in people of any age who are at higher risk of blood clots because of their medical condition only if the benefits from the protection from Covid-19 infection outweighs potential risks.

France and Germany now recommend that people under the age of 55 and 60 years respectively who have had a first dose of the Oxford/AstraZeneca vaccine are given a different vaccine for their second injection. This mixed-dose approach has been recommended by the Haute Authorité de Santé in France despite little clinical trial data to support it, although trials involving a combination of vaccines including the AZ vaccine and Russia’s Sputnik V vaccine are in progress. 

Spain and Italy have limited the use of the vaccine to those over 60 years of age and the UK has said that under 30s should be offered an alternative vaccine.

So in conclusion, is there a risk of thrombosis with the AZ vaccine? – probably, but not definitively proven, the risk is very much lower than the risk of dying from Covid-19 in my age group, or from contracting Long Covid. Would I have the AZ vaccine? – yes I already have and will have the second dose. Which vaccine would I have if I was given a choice? – probably the Moderna or Pfizer vaccine, but only because their efficacy is higher.

The development of the current anti Covid-19 vaccines in a relatively short time is a remarkable achievement. Much of this is down to the adaptation of an existing technique and the removal of many of the usual bureaucratic and financial constraints on scientific research. The vaccines have proved to be safe and effective, but like every medical treatment will certainly be found to carry some risks. The challenge in the coming months is to evaluate these risks and the mechanisms behind them to reduce these to a minimum. Mass vaccination to achieve herd immunity will require 70-80% of the population to be either immune or vaccinated and is our only way out of the pandemic in the near future. Sadly it is still going to be some time possibly years before we can go back to what in retrospect seems like a very free and unrestricted life.

This article first published on 11 April 2021.

To read previous articles from Dr Kevin, click here.

Pic: Rosie Jackson
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