ZURICH (Reuters) – European drug regulator said on Wednesday it had found a possible link between AstraZeneca’s COVID-19 vaccine and very rare blood clots in adults who received the shot. Britain recommended that people under the age of 30 have a COVID-19 alternative vaccine if possible.
Here’s what we know so far:
WHAT HAPPENED?
The EMA said its vaccine side effects control system, as of April 4, had received 169 reports of cases of cerebral venous sinus thrombosis (CVST) or clots in blood vessels coming out of the brain and 53 cases of splanchnic venous thrombosis (SVT), or coagulation in the veins of the abdomen.
This represents about 34 million doses of AstraZeneca vaccine administered in Britain and the European Economic Area since vaccinations began almost three months ago.
Its safety committee conducted a review of 62 cases of CVST and 24 cases of SVT, of which 18 were fatal.
Most of the reported cases have occurred in women under the age of 60, although this could be misleading. Germany and Britain say many more women received the AstraZeneca shot than men.
Most cases occurred 2 weeks after the person received the first dose.
German vaccination officials who recorded 29 cases of CVST in women aged 20 to 59 who received the AstraZeneca vaccine said the incidence rate in this group was 20 times higher than 16 days after vaccination than usual had been expected.
The German Ministry of Health has said that 1 to 1.4 cases of CVST would have been expected during this time.
WHAT HAS THE BRITISH REGULATOR SAID?
The Medicines and Health Products Regulatory Agency reviewed 79 cases of rare coagulation along with low platelets, with 19 fatalities: 13 women and 6 men. Eleven of the deaths in people under 50 and three under 30.
All 79 cases occurred after a first dose of vaccine.
HOW DID THE REGULATORS REACH THEIR DECISION?
British officials relied on statistics from the Winton Risk and Evidence Communication Center at Cambridge University to explain their recommendations for young people to receive an alternative while older people still receive AstraZeneca.
According to the center, vaccination with AstraZeneca shot would reduce nearly seven admissions to intensive care units per 100,000 people in the group between the ages of 20 and 29 with a high risk of exposure to the virus, while 1.1 people for every 100,000 people in it it was estimated that the group was likely to suffer serious vaccine-related damage.
The risk of serious harm due to vaccination decreases even more as the elderly get it, and admissions to the ICU prevented by vaccination increase sharply, which increases the benefit-risk ratio of taking AstraZeneca. The Center concluded that only 0.4 people per 100,000 of the 50-59 year olds would suffer vaccine-related damage, while 95.6 admissions to the ICU per 100,000 people would be prevented.
EMA researchers checked whether the frequency of events was higher in the vaccinated population than normal fund rates extracted from public health statistics or insurance records. This would be combined with a medical analysis of each case and a view of the scientific literature.
In its findings, the EMA said on March 18 that, on average, normally only 1.35 cases of CVST could be expected among people under the age of 50 in the 14 days following the AstraZeneca vaccine, while by the same deadline, 12 cases had been registered. .
In comparison, four women in 10,000 would get a blood clot by taking oral contraceptives.
The conclusion of the likelihood of an increased risk of clotting, compared to the benefits of preventing COVID-19 and reducing hospitalizations and deaths, is key to the EMA’s assessment that the benefits continue to outweigh the risks.
WHAT IS THE EU DOING NOW?
The EMA said that unusual blood clots with low blood platelets should be listed as very rare side effects and that countries should decide how to proceed with their national immunization campaigns against COVID-19.
These can vary from country to country, depending on the EMA, depending on factors such as how quickly the infections spread and whether vaccines are available. Its safety committee called for new studies and changes to existing ones to provide more information about the mechanism behind rare clots.
AstraZeneca and European regulators have said concerns about blood disorders did not arise during clinical trials.
IS THERE ANY THEORY FOR WHAT I COULD LEAD TO THE HOLES?
Among the possible causes of these rare sinus cerebral vein clots that are being investigated is that the vaccine triggers an unusual antibody in rare cases.
The EMA said the vaccine can trigger an immune response that leads to unusual clotting, although it acknowledged that scientists have not yet identified any risk factors that could predispose someone to clotting combined with low platelets.
German scientists at Greifswald University concluded that the vaccine is related to side effects, although their work still requires a peer review. Andreas Greinacher, an expert on drug-induced immune responses, said the specimens he examined had unusual antibodies that activate blood platelets, causing clots.
Greinacher continues to look for clues as to why some people had clots and others didn’t.
Report by Ludwig Burger in Frankfurt, Matthias Blamont in Paris and John Miller in Zurich; Additional reports by Kate Kelland and Alistair Smout in London and Julie Steenhuysen in Chicago; Edited by Josephine Mason and Angus MacSwan