The study found that the incidence rate of Guillain Barre syndrome increased after receiving AstraZeneca new crown vaccine
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However, the scientists say it is still unclear why this link exists. In addition, the small number of cases of Guillain Barre syndrome observed appears to be similar to the increase previously seen in other mass vaccination campaigns.
The same research team at the Queen’s Square Institute of Neurology, University College London, has previously shown that there is no measurable link between covid-19 infection and GBS. This follow-up study was designed to investigate any relationship between covid-19 vaccination and GBS.
Guillain Barre syndrome (GBS) is a rare but serious autoimmune disease that attacks the peripheral nervous system, usually leading to limb weakness, numbness and pain, and sometimes respiratory paralysis. GBS often occurs after infection, especially a gastroenteritis infection called Campylobacter. The immune system mistakenly attacks the nerves rather than the bacteria.
GBS is usually reversible, but in severe cases, it can lead to long-term paralysis involving respiratory muscles, requiring ventilator support, and sometimes leaving permanent neurological dysfunction. Early detection by a professional neurologist is the key to correct treatment.
For the study published in the journal Brain, scientists conducted a population-based study on NHS data to track the GBS case rate and vaccination promotion. In addition, as part of a separate study of UK hospital surveillance data, they studied the phenotypes (characteristics / symptoms) of reported GBS cases to determine whether there were any specific characteristics of GBS associated with covid-19 vaccine.
The researchers observed that 996 GBS cases were recorded in the UK National immunoglobulin database from January to October 2021, but there was an unusual peak of GBS reporting between March and April 2021. In these two months, there were about 140 cases per month, compared with the historical rate of about 100 cases per month.
To determine whether these cases were related to vaccination, they linked the date of onset of GBS to vaccination data for each person in England’s national immunization management system.
Analysis showed that 198 GBS cases (20% of 966 cases) occurred within six weeks after the first dose of covid-19 vaccine in England, equivalent to 0.618 cases per 100000 vaccinations. Among them, 176 people have been vaccinated with AstraZeneca vaccine, 21 people have been vaccinated with Pfizer vaccine, and 1 person has been vaccinated with Moderna. Within six weeks of any second dose of vaccination, only 23 cases of GBS were reported.
In general, after the first dose of AstraZeneca vaccine, there are 5.8 excess GBS cases per million doses of vaccine, equivalent to 98-140 absolute excess cases from January to July 2021. Neither the first dose of Pfizer and Moderna nor the second dose of any vaccine showed any excess GBS risk.
Commenting on these figures, the lead author Professor Michael Lunn (UCL Queen’s Square Institute of Neurology) said: “there were a large number of GBS cases within 2 to 4 weeks after vaccination. A case peak was observed around 24 days after the first dose of vaccine.”
“The first dose of AstraZeneca vaccine accounted for most or all of this increase. No similar pattern was seen after the second dose of other vaccines or any vaccine.”
In a separate phenotypic study, researchers used a UK wide multicenter (four country) hospital data set to collect event data of GBS cases reported by clinicians from January 2021 to November 2021. At the end of this analysis, the researchers found that compared with non vaccinated cases, there were no specific clinical features, including facial weakness (which received special attention in the medical literature) and GBS related to vaccination, which showed how difficult it was to detect vaccination related cases from normal background cases.
Professor Lunn said: “Only the reason for the association between AstraZeneca vaccination and GBS is unclear. There is no strong or possible increase in GBS risk due to covid-19 infection, and there is no increase in the risk related to Pfizer vaccination, which means that covid-19 spike protein is unlikely to be the pathogenic factor for the increased risk. The viral vector used to carry nucleic acid in AstraZeneca and similar vaccines may be the reason, but this needs to be further explored.”
Historical background of vaccine related GBS
During the swine flu vaccination campaign in the United States in 1976, GBS related to the new influenza vaccine at that time increased slightly. At that time, the vaccination campaign was stopped because the risk of GBS was statistically higher than the background (normal time), although subsequent statistical analysis found that the risk of this association was lower than initially thought.
The excess incidence rate after the first dose of AstraZeneca vaccine is estimated to be 5.8 cases per million doses, which is similar to the estimation of 1976 “swine flu” vaccine and higher than the reported excess cases of modern influenza and yellow fever vaccines (but in the same order of magnitude). This is well below the 1 in 1000 GBS incidence rate associated with Campylobacter jejuni gastroenteritis or Zika virus.
Professor Lunn added: “at present, we do not know why the vaccine may cause these very small increases in GBS. It may be that non-specific immune activation has occurred in susceptible individuals, but if so, similar risks may apply to all vaccine types.”
“Therefore, it is logical that simian adenovirus vectors, which are often used to develop vaccines, including AstraZeneca vaccines, may be the reason for the increased risk.”
“In previous studies, there is no strong association between adenovirus and GBS, and any association between adenovirus vaccination and GBS has only been reported once. However, in the UK, adenovirus testing is not routinely performed in GBS cases. Whether adenovirus may account for part of ‘idiopathic’ (no known cause) or ‘sars-cov-2 negative’ GBS may be the subject of further research.”