How COVID-19 jab side effects affect your immune system
Exclusive: People who experience side effects from the COVID-19 jab do not necessarily gain greater protection from the virus, nor are they more susceptible to it, experts said.
Almost half the Australians who've had their vaccine have reported adverse reactions - and a third felt like they had the flu.
But, while it seemed logical, there was as yet no clinical evidence linking a person's severe side effects to the jab to them getting a potentially harsher version of COVID-19.
"Just because you got a severe reaction to the vaccine doesn't mean you'd get a severe reaction if you got the infection, although it might seem there's some logic in taking them to be related," University NSW virologist Professor Bill Rawlinson told News Corp.
He said for people with severe COVID-19, often it was their body's immune system over reaction causing some of their health problems not the virus itself.
However, he said he was unaware of any studies that could prove people who had a strong reaction to the vaccine would have developed severe COVID-19.
Australian Catholic University infectious diseases expert Dr Roger Lord said "the short answer to your question is no".
The vaccine contains a compound that stirs up the immune system, called an adjuvant.
And often its these adjuvants in the vaccines that can cause severe responses.
The vaccines also contain fragments of the virus that cause COVID-19 and these can
be in higher amounts than if a person was naturally infected with the viru, he said.
"Some rare adverse effects seen for vaccines directly relate to how the vaccine is formulated," he said.
University Queensland's Professor Paul Griffin, who has conducted clinical trials on six leading COVID-19 vaccines, said "side effects don't necessarily tell us very much at all about the immune response".
"Some people can have absolutely no reactions and still have a good response and, you know, conversely, some people can have some side effects and not necessarily have the most potent of responses so unfortunately it's not quite as simple as that," he said.
While only half the people in clinical studies had a reaction to their vaccine up to 95 per cent were protected by the vaccines.
A prepublication of a study at Mount Sinai Hospital that has not been peer reviewed found the antibody levels of people vaccinated after they had been infected with COVID were 10-20 times higher than those who had not had the illness.
A very small study of 44 vaccinated people at the University of Pennsylvania published in journal Science Immunology found people who reported systemic side effects such as fever, chills and headache may have had somewhat higher levels of antibodies to the pandemic virus.
However, these people did not have a more potent response in the long term part of their immune system- the memory B cell response, the study found.
The immune system responds to vaccines in two ways.
The initial innate immune response happens as soon as your body notices you've been exposed to the a virus and it sends white blood cells called neutrophils and macrophages to destroy it.
The first line of defence lasts a few days.
Weeks latera second line of defence kicks in its called the adaptive immune response and it relies on T and B cells that learn to recognise the virus.
If you encounter the virus months after being infected or being vaccinated these immune cells recognise it and start generating antibodies to it.
VACCINE SIDE EFFECTS REVEALED
What we do know is women (16.2 per cent) are more likely to have severe side effects such as anaphylaxis than men (9.3 per cent) after the first dose of Pfizer's vaccine.
After the AstraZeneca jab, 39.3 per cent of women had a reaction compared to 26.2 per cent of men.
An AusVaxSafety survey of over 316,000 Australians who have been vaccinated against COVID-19 found nearly half reported an adverse event, the most common being pain at the injection site.
For the AstraZeneca jab, side effects were more common after the first dose (58.6 per cent) but for Pfizer side effects were more common after the second shot.
Only 34 per cent had a side effect after the first dose of Pfizer compared to 57 per cent who had a side effect after the second dose.
After the second dose of Pfizer, 45.8 per cent suffered fatigue, 41.8 per cent had a headache, 37.5 per cent had muscle aches, 24.2 per cent had joint pain and 16 per cent had a fever.
After the first dose of the AstraZeneca jab, 46.2 per cent suffered fatigue, 38.5 per cent had a headache, 35.7 per cent had muscle aches, 22.5 per cent had joint pain, 22.5 per cent had a fever and 28.5 per cent suffered chills.
Originally published as How COVID-19 jab side effects affect your immune system