Thursday, April 08, 2021

The Oxford - AstraZeneca Jab

I've had a first dose of the Oxford/AstraZeneca COVID-19 vaccination three weeks ago. I had no side-effects whatsoever, and unless very dramatic new evidence turns up in the meantime prompting any further change of medical and scientific advice, I shall have no hesitation at all in having the second jab when it is due.

The only clots I am worried about are Anti-Vaxxers.

Both the UK and European medicine safety regulators say that the jab is safe and effective and saves lives.

Because the effects of the vaccination rollout is being extremely carefully monitored, it has been found that of the 20 million people in the UK who have had the Oxford/AstraZeneca vaccine, 79 have developed a type of rare blood clot, of whom 19 have died.

You don't need to be Alan Turing to work out that this is slightly less than four people in a million who have had the vaccine and also had blood clots, and slightly less than one in a million who actually died with them.

The regulators have pointed out that there is no proof of a causal relationship between the vaccination and the blood clots - a certain small number of people get these clots anyway. Anyone who assumes that the vaccine caused all these clots is making a mistake so old that scholars of logic usually refer to it by the latin name it was first given many hundreds of years ago - post hoc ergo propter hoc

That is latin for "After this, therefore because of this," something which does not necessarily follow. As per my quote of the day, correlation does not prove causation. 

This type of clotting is very rare, but some people do get these clots anyway, and since 60% of UK adults have had a COVID vaccination, the majority of whom have had the Oxford/AstraZeneca vaccine, it is almost certain that the group of people vaccinated will include a substantial proportion of the people who were already going to develop these blood clots and would have done so whether they had had the vaccination or not. 

It is possible that there may be a correlation, and that that this may be a result of a causal relationship, but as I understand it the scientists are still cautioning us that it has not been proved. And even if it exists the risks are very low indeed, both compared to the risks of dying of COVID-19 and the risks of developing blood clots for other reasons - including COVID-19.

Even if the vaccination did cause these clots, someone my age would be more than a thousand times more likely to die, or for that matter get blood clots, as a result of COVID-19 if I hadn't had the vaccine than I actually am of getting them as a result of having taken the jab. COVID-19 causes side effects too, and one of the things it is associated with is a higher incidence of blood clots. Of cause, correlation does not prove causation in that case either but it is at least as likely.

The same would be true of all the people in their forties and fifties or above who are being offered the vaccination at the moment. Anyone who is concerned that they might be particularly vulnerable to blood clotting or any other issue should seek medical advice from their GP or another medical professional with relevant qualifications.


The review by the Medicines and Healthcare products Regulatory Agency (MHRA) found:

  • Nearly two-thirds of the cases of rare clots were seen in women
  • The people who died were aged between 18 and 79, with three of them aged under 30
  • All the recorded cases occurred after the first dose, although the lower number of second doses meant it was not possible to draw any conclusions from this

Meanwhile, the EU's medicines regulator, the EMA, says unusual blood clots should be listed as a possible very rare side effect of the AstraZeneca jab, but that the benefits outweighed the risks

The World Health Organization said the link between the vaccine and blood clots was "plausible" but not confirmed, adding that the clotting incidents were "very rare" among nearly 200 million people who have received the jab worldwide.

Health Secretary Matt Hancock said the UK's review confirmed that the Oxford-AstraZeneca jab is "safe, effective and the benefits far outweigh the risks for the vast majority of adults".

Prime Minister Boris Johnson said the AstraZeneca vaccine had "already saved thousands of lives" and the new advice should ensure people of all ages "continue to have full confidence in vaccines".

Labour leader Sir Keir Starmer also urged people to "trust in our doctors and scientists" and said he was looking forward to receiving his second AstraZeneca dose.

AstraZeneca said both the MHRA and the EMA reviews reaffirmed that the benefits of the vaccine "continue to far outweigh the risks".


The MHRA is recommending, however, that when the vaccination rollout reaches people aged 18 to 29 for whom the balance of risk is less overwhelming, they should have the option of taking one of the other vaccines rather than the Oxford/AstraZeneca jab.


 June Raine, chief executive of the MHRA, said the side-effects of the AstraZeneca vaccine were "extremely rare" - and more work was going to identify if the vaccine was definitely causing the clots.


"The balance of benefits and known risks is still very favourable for the majority of people," she said.


But she said for younger age groups it was more "finely balanced".


She added: "The public's safety is at the forefront of our minds." 


Professor Lim Wei Shen, of the JCVI, (Joint Committee on Vaccination and Immunisation) said the move was being made "out of the utmost caution rather than because we have any serious safety concerns".


Professor Sir Munir Pirmohamed, chairman of the Commission on Human Medicines, said the risks had to be weighed against the consequences of Covid-19, which also causes clotting.


He said 7.8% of coronavirus patients suffer blood clots on the lungs, while 11.2% will suffer deep vein thrombosis (DVT) in the legs.


People who have had their first dose of the AstraZeneca vaccine should still get their second dose, the MHRA said. Only those who suffered one of these rare blood clots after the first dose should not get vaccinated, it added.


Pregnant women and people with blood disorders that leave them at risk of clotting should discuss the benefits and risks of vaccination with their doctor before going for a jab.


Anyone who suffers symptoms such as a persistent headache, blurred vision or confusion for four days or more after vaccination or who experience unusual skin bruising, shortness of breath or chest pain are being asked to seek medical advice.


England's deputy chief medical officer, Prof Jonathan Van-Tam, described the move as a "course correction" - and said it was normal in medicine to change preferences in this way.


He also said the impact on the government's promise to offer all adults a jab by the end of July should be "zero or negligible" as long as the expected supplies of the Pfizer and Moderna vaccines - the other two Covid vaccines in use in the UK - arrived as expected in the coming months.


The source for much of the information in this post is an article on the BBC website here.

5 comments:

Jim said...

There is never an absolute. There never will be. No vaccine can ever be 100% safe. Nothing can, everything causes cancer is the usual term isnt it. So something being Safe is a pretty pointless statement. Kind of like a safe investment (there is no such thing)

what is imporant is the risk / benefit ratio.

on the whole for the entire population is also a pointless calculation in this case, we are vaccinating individuals, each of which has a differnt score each side of the risk/benefit ratio.

for a lot of people, myself included being an old git at 45, the benefit outwieghs the risk. using this info in the guardian out of every 100,000 cases of people my age 5.7 have ICU admissions, the vacine only harms 0.5, so the benefit wins

BUT in the 18-29 age group only 0.8 out of every 100,000 cases needs ICU treatment, yet serious harm from the vaccine affects 1.1

The scale has tipped the other way.

One other question though, and whilst i appreciate its a joke line when you say "The only clots I am worried about are Anti-Vaxxers."
well, logically why would you be? even if they do manage to catch and start spreading covid, if the vaccine works then to be logical you are in no danger are you :)

Chris Whiteside said...

I agree with almost all of that - no medicine or vaccination is completely free of any risk, however tiny, of side effects, but for the vast majority of people the risk of dying of COVID if you don't have a jab is still far greater than the risk of getting a blood clot if you do - and that's even if there is a causal relationship, which has not been proved.

I did refer to the risk for different age groups such as yours and mine and for anyone over thirty the balance of risk is very heavily in favour of having the jab.

But yes, the balance of risk is less overwhelmingly in favour of the Oxford/AstraZeneca jab for those under thirty, which is why the regulators have recommended, and the government has agreed, that those aged 18-29 will be given one of the other vaccines such as Pfizer/BioNTech or Moderna.

The comment about Anti-Vaxxers was indeed a joke, but it was a joke with a core of truth.

Anti-Vaxxers - defined as those who spread myths or misunderstandings which undermine public confidence in a safe and effective vaccine - are not just putting their own lives at risk but those of others such as the minority for whom the vaccine is not effective or who have a valid medical reason why they cannot take it.

The concept of "herd immunity" was rather badly abused earlier in the pandemic when it came to be seen as indicating if you let the pandemic rip "Herd Immunity" would somehow substitute for taking action to protect people.

However, when the terms is used properly, Herd Immunity is a real thing - if you give a small number of people an effective vaccination it protects them, if you give nearly everyone the vaccination, then Herd Immunity provides an extra benefit which protects everybody. Anti-Vaxxers undermine that benefit.

Jim said...

again there is a flaw, you see the vaccine cant 100% stop you getting covid and its not assumed it stops you spreading it either. Thats why you still have to wear the masks and things. So its not just the anti vax brigade that could potentially pass the virus to those who cant have the vax on medical grounds.

Im not one of the anti vax brigade, though i have always thought you know, consequence of your own actions. I kind of like the Darwin awards given to those to remove stupid genes from the gene pool.

I have no objection to Jehovahs witnesses who refuse to have life saving blood transfusions. I have no objection to an adult refusing to be vaccinated against TB or Measles either. The only time i object to the either of the above is when people are making that desision for others, usually, their kids.

we never condemned anyone for not having a flu jab, and if someone refused it and died of flu, well isnt that the consequence of your own actions. Flu is of course contagious, but we never ever said to anyone if you dont get the flu jab you are part of the problem did we.

Chris Whiteside said...

Jim, I never thought you were one of the Anti-Vax brigade.

Nor am I suggesting that vaccination should be made compulsory - there are some people for whom not having a given vaccination may be a rational choice and attempting to use compulsion might do more harm than good.

The key thing is that vaccination is one of the most effective tools which we can use to get the rate of transmission of the disease down to a point where far fewer of those who are vulnerable come into contact with the disease. A vaccination does not have to be 100% effective to drive down the infection rate - in current jargon, to get the "R" rate well below one. 80% or so should be enough to drive a huge reduction in the "R" rate.

If paranoid myths about vaccinations were to reduce people's willingness to take the vaccine enough stop that happening - and, thank God, it would appear so far that the vast majority of the British people have too much sense to have allowed that to happen - then the myths spread by anti-vaxxers could end up causing more deaths among the minority for whom the vaccine is not effective, or have a good reason not to take it, than would otherwise be the case.

Chris Whiteside said...

I am willing to engage on this subject with anyone who has something constructive to say, whether I agree with them or not.

Comments signed with all or part of the name of the person commenting or a consistent nickname will be allowed to stay up on this thread.

Anonymous trolls with nothing to say but insults and without the guts to sign their own name have nothing worthwhile to contribute and such comments will be deleted.