The AstraZeneca vaccine may increase the risk of the serious neurological condition Guillain-Barré syndrome (GBS) with the jab’s Trojan horse delivery system possibly to blame, scientists believe, in a discovery which may apply to similar vaccines.

GBS is a rare condition which causes muscle numbness and pain, and can hinder movement, walking, swallowing and, sometimes, even breathing. It is commonly caused by the gastroenteritis bug Campylobacter, which has a surface coating which looks slightly human, and so can sometimes trigger the body to attack its own nerves instead of invading germs, leading to GBS. Now, scientists at University College London (UCL) have found a rise in cases of GBS in the first two to four weeks after the AstraZeneca vaccine, but not in other vaccines, such as Pfizer or Moderna.

Like many vaccines, the Oxford jab uses a weakened chimp adenovirus to deliver the coronavirus spike protein into the body, and scientists have speculated that a reaction to adenovirus may be responsible for the rise in cases. Adenovirus usually causes the common cold, but scientists are starting to think it may also mimic human cells in a similar way to Campylobacter, confusing the immune system into attacking the body.

Lead author Prof Michael Lunn (UCL Queen Square Institute of Neurology) said: “At the moment we don’t know why a vaccine may cause these very small rises in GBS. “It may be that a non-specific immune activation in susceptible individuals occurs, but if that were the case similar risks might apply to all vaccine types.

“It is therefore logical to suggest that the simian adenovirus vector, often used to develop vaccines, including AstraZeneca’s, may account for the increased risk.” Adenovirus-based vaccines are used against a wide variety of pathogens, tuberculosis, HIV and malaria. GBS affects about 1,500 people in the UK each year and 30 to 40 per cent of cases have no known causes, leading researchers to suspect that adenovirus could be a factor. During the 1976 swine flu vaccination campaign in the USA, there was a small increase in GBS associated with the flu jab at that time, leading scientists to question whether the Covid jabs could have a similar effect.

To find out, UCL researchers carried out a population-based study of NHS data in England to track GBS case rates against vaccination rollout. Between January to October 2021, 996 GBS cases were recorded in the UK neurological condition National Immunoglobulin Database, but there was an unusual spike in GBS reports occurring between March and April 2021. For these two months there were about 140 cases per month compared to historical rates of about 100 per month – a 40 per cent increase. Analysis showed 198 GBS cases (20 per cent) occurred within six weeks of the first-dose Covid-19 vaccination in England.

Overall, following a first dose of the AstraZeneca vaccine there were 5.8 excess GBS cases per million doses of vaccine, equating to an absolute total excess between January-July 2021 of between 98-140 cases. The rate is still significantly lower than the one in 1,000 rate of GBS associated with Campylobacter. Data suggest Johnson & Johnson vaccine raises GBS risk
Recent data from the US also suggests that the Johnson & Johnson Janssen vaccine – which also uses an adenovirus entry system – raises the risk of GBS to similar levels as the AstraZeneca jab. “We know that Pfizer and Moderna don’t cause BDS but Johnson & Johnson and AstraZeneca do and the only commonality link is an adenovirus vector,” added Prof Lund. “Johnson & Johnson is not the same one because they use a human adenovirus but it’s similar and the implications are broad because adenoviruses are used in quite a lot of vaccines and genetic therapies.

“The benefits from these vaccines and drugs are huge and the risk is tiny and there aren’t that many viral vectors you can use, but it’s good that the public are aware of the risks. “And theoretically, if we know what virus is causing GBS, we can turn it off and we might be able to prevent disease progression.”

The new research was published in the journal Brain. An AstraZeneca spokesman said: “Guillain-Barre Syndrome (GBS) has been reported very rarely following vaccination with Vaxzevria. Vaccination of any kind is a known risk factor for GBS and it is noted in the manuscript that the small number of GBS cases appears similar to increases previously seen in other mass vaccination campaigns.

“It should also be noted that in the UK, Vaxzevria had been administered to more people than any other neurological condition vaccine during the time frame studied in the manuscript. “The study observes that the small numbers of cases should be compared to how many infections, hospitalisations and deaths our vaccine has prevented due to Covid-19. Current estimates show that globally the vaccine has helped prevent 50 million Covid-19 cases, five million hospitalisations, and to have saved more than one million lives.

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