Covid booster: Why is AstraZeneca not being used – the side effects
JCVI expert warns booster vaccines will wear off
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More than 37 million Covid booster doses have been administered across the UK. The majority of these doses have included either Pfizer or Moderna. Many may wonder why only two are recommended. Is the AstraZeneca Covid booster safe?
Findings from the CovBoost study, which assessed the effects of third doses on the body’s T cell immune response after a booster shot, back up the UK’s decision to offer either the Pfizer or Moderna vaccines as a third dose, with the mRNA jabs giving the most significant rise in immunity levels by comparison to other vaccines.
Professor Saul Faust, trial lead and director of the NIHR Clinical Research Facility at University Hospital Southampton NHS Foundation Trust, said: “All of the vaccines in our study do show a statistically significant boost.
“RNA (Pfizer and Moderna) very high, but very effective boosts from Novavax, Janssen and AstraZeneca as well.”
The Pfizer, Moderna and AstraZeneca vaccines have all been approved for use as a booster by the Medicines and Healthcare products Regulatory Agency (MHRA).
However, the Joint Committee on Vaccination and Immunisation (JCVI) has recommended only using the two mRNA vaccines (Pfizer and Moderna) where possible.
These have been proven to have fewer side effects and a stronger immune response.
What is the safety concern for the AstraZeneca booster jab?
The MHRA advised against giving the AstraZeneca vaccine to people under the age of 40 earlier this year due to its link to blood clots.
People in this age group are instead being offered either the Pfizer or Moderna vaccines as the balance of risk is “more finely balanced” among younger age groups, who do not tend to suffer serious illness from Covid-19.
Scientists believe they have now identified the “trigger” behind the rare blood clot complications from the jab.
An international team of researchers in Cardiff and the US have said the reaction can be traced to the way a component of the vaccine binds with a specific protein in the blood.
Researchers believe this may cause a chain reaction in the immune system which can lead to the development of blood clots, a condition known as vaccine-induced immune thrombotic thrombocytopenia (VITT).
Professor Alan Parker, from Cardiff University’s School of Medicine, said: “VITT only happens in extremely rare cases because a chain of complex events needs to take place to trigger this ultra-rare side effect.
“Our data confirms PF4 can bind to adenoviruses, an important step in unravelling the mechanism underlying VITT. Establishing a mechanism could help to prevent and treat this disorder.
“We hope our findings can be used to better understand the rare side effects of these new vaccines – and potentially to design new and improved vaccines to turn the tide on this global pandemic.”
Other side effects from the AstraZeneca vaccine include:
- Increased body temperature
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