COVID: New theories called AstraZeneca bullet linked to blood clots

Scientists are studying a number of possibilities that could explain at least 18 reports of rare blood clots in the brain that occurred in individuals in the days and weeks after their onset. AstraZeneca COVID-19 vaccine.

European researchers have put forward one theory that the vaccine stimulates a rare antibody in some rare cases; Others are trying to figure out if the issues are related to birth control pills.

But many scientists say there is no conclusive evidence and it is not clear whether or why the AstraZeneca vaccine would cause an issue that is not shared by other vaccines targeting the same type. the coronavirus.

The majority of rare blood clots have been seen in women and the majority of cases have been reported in Europe. Two cases have been reported in India.

The European Medicines Agency said an initial review shows the vaccine is not linked to an increase in the overall risk of blood clots. But it did not regulate association with rare cases of blood clots in vessels draining the blood from the brain called cerebral venous sinus thrombosis (CVST).

Researchers in Germany and Norway, where some of the cases were reported, this week thought that the vaccine could stimulate an immune response in which the body makes antibodies to the body. may cause blood clots.

Professor Paal Andre Holme of Oslo University Hospital in Norway, who treated three health care workers with severe blood clots after receiving the AstraZeneca vaccine, said at a news conference on Thursday that we ” has found findings that could “explain the clinical progress of our patients.”

Holme warned that the decisions were preliminary. “This is just the beginning of the research that is being done,” he said, adding that he did not release any data to support his hypothesis.

A team of German researchers at the Greifswald University Clinic said on Friday that they had reached a similar conclusion. If diagnosed correctly, there may be a way to treat a condition, the experts said.

EMA researchers said Thursday that they are conducting several studies to determine if the rare blood clots could be linked to the vaccine, or if they could occur by chance. They noted that many of the incidents occurred in younger women.

CVST, although rare, has been associated with obesity and the use of oral contraceptives. “That’s one of the things we’ll be exploring further soon,” said Sabine Straus, chair of the EMA safety committee.

EMA is also planned to investigate whether those who developed the condition had the disease before or at the time of vaccination with COVID-19, which could cause blood clots.

Several U.S. vaccine experts remain cautious about the antibody hypothesis and said that the high level of visibility of the events could lead to more clinicians reporting the condition than usual, which would make it likely the events are related to the vaccine.

AstraZeneca vaccine has been granted emergency use in 70 countries, but has not yet been approved in the United States.

U.S. experts also question why such events would only occur at higher rates with the AstraZeneca vaccine and not with the vaccines with Pfizer Inc and BioNTech SE, Moderna Inc, Johnson & Johnson and the Sputnik V vaccine. Russia – they all intend to produce targeted antibodies. at the “spike” portion of the coronavirus it uses to enter cells.

Like the J&J and Sputnik vaccine, AstraZeneca uses a non – reproducible cold virus called adenovirus to deliver spike proteins to cells and trigger an immune response.

“We need to see when (German and Norwegian scientists) submit peer-reviewed publication and can be reviewed by the scientific community,” said Dr. Peter Hotez, vaccine researcher at Baylor College of Medicine in Houston. “There is no reason why the AstraZeneca vaccine would do this while the others would not, including the adenovirus – based COVID-19 vaccines.”