![]() ![]() What this means is that the white blood cells that are stimulated by the vaccine to make antibodies themselves have to secrete chemicals called cytokines, interferons and chemokines, which function to send messages from cell to cell to become activated.” “The other common side-effects – the muscle aches, flu-like illness and fatigue – are probably due to generalised activation of the immune system caused by the vaccine. “The sore arm can be either due to the trauma of the needle in the muscle, or local inflammation in the muscle probably because of the chemicals in the injection,” said Prof Robert Read, head of clinical and experimental sciences within medicine at the University of Southampton and director of the National Institute of Health Research’s Southampton Biomedical Research Centre. While the UK has ordered 30m doses of the J&J jab, it has not yet been authorised for use by the MHRA. However, experts say it is too soon to be sure the J&J jab is causing the blood-clotting problem, and even if it is, the risk is very low. “This seems to be an issue with DNA adenovirus vector vaccines – the biology of which is yet to be fully understood,” said Prof Saad Shakir, director of the independent Drug Safety Research Unit. However, while the AstraZeneca jab uses a chimpanzee cold virus, the J&J jab uses a human cold virus to do so. Both use cold viruses that cannot replicate to deliver instructions for making the coronavirus spike protein into human cells: the cells then produce the protein, triggering an immune response. The AstraZeneca and J&J jabs are based on a similar technology. The US Food and Drug Administration has recommended pausing use of the jab while J&J has announced it would “proactively delay the rollout of our vaccine in Europe”. Investigations are also under way into the Johnson & Johnson (J&J) Covid jab amid concerns it may be linked to a similar blood-clotting problem: so far six cases of CVST with low platelets have been reported amid 6.8m doses of the vaccine given in the US, all of which were in women aged between 18 and 48. Other countries have taken different approaches: in France the AstraZeneca jab is now only to be given to those aged 55 and over, while in Germany it is offered to those aged 60 and over. ![]() “Although the chance of any person receiving the vaccine experiencing a blood clot with low platelets is extremely small, because the risk of severe Covid in the under-30s with no underlying illness is also small, JCVI feel as a precautionary measure it is appropriate for those in this age group to be offered an alternative Covid vaccine when their turn comes for their first dose of a vaccine,” said Prof Anthony Harnden, deputy chair of the JCVI. In other words, the benefits of the jab far outweigh the risks.īut for young adults that equation, at least at present, is less clearcut.Īs a result the UK’s Joint Committee on Vaccination and Immunisation (JCVI) has recommended that adults under the age of 30 should be offered alternative Covid vaccines – if available – provided they were healthy and at low risk of Covid. What is more, they note that for most people the risk posed by Covid is much greater than the chance of serious harm from a Covid jab, and that Covid itself can cause dangerous blood clots. However, cases remain very rare: the MHRA noted 79 cases of blood clots with low platelets, including 19 deaths, following more than 20m doses of the AstraZeneca jab, with 44 of the cases and 14 of the deaths related to a rare type of blood clot in the brain called cerebral venous sinus thrombosis (CVST) that occurred with a low platelet count.Įxperts have stressed the rarity of such cases estimating they may occur in about one in 100,000 young adults who get the jab – a risk lower than the chance of dying in a road accident in a year. Based on the currently available evidence, specific risk factors have not been confirmed,” the EMA said. “So far, most of the cases reported have occurred in women under 60 years of age within two weeks of vaccination. Are blood clots a side-effect of the vaccines?Ĭoncerns have been raised about a particular situation whereby certain blood clots have occurred together with low levels of platelets – tiny cells in the blood that help it to clot.Įarlier this month the MHRA said that while not yet proved, there was growing evidence to suggest this syndrome could be caused by the AstraZeneca jab, while the European Medicines Agency said there was a possible link and noted the syndrome should be listed as a very rare side-effect of the vaccine. Early reports that some people had severe allergic reactions, particularly to the Pfizer jab, led the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) to offer new recommendations, including that anyone receiving the Pfizer jab be monitored for 15 minutes after the event.
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