Millions of people in dozens of countries have received the AstraZeneca covid vaccine with reports of some effects, and its prior testing in tens of thousands has found it safe.
But recently, a small number of vaccine recipients in European countries have suspected its safety by blood clots and abnormal bleeding, although no causal link has been found between patients’ conditions and the vaccine. The report shows more than a dozen countries have either partially or completely suspended the use of the vaccine while the cases are investigated. Most countries said they were doing so as a precaution until major health agencies could review the cases.
The AstraZeneca vaccine has not yet been authorized for use in the United States, although its US trial is expected to be reviewed soon.
What kinds of problems led countries to take precautionary measures?
The cascade of decisions by mainly European countries to stop the use of AstraZeneca vaccine, followed reports of four serious cases in Norway, described in health workers under 50 who received the vaccine Was. Most developed clots or bleeding abnormalities and had low platelet counts, health officials said. Two of them died of brain hemorrhage and the remaining two are hospitalized. The death of a 60-year-old woman in Denmark and a 57-year-old man in Italy also sparked quick decisions, although none of the deaths have been fully investigated to see if there is a link to the shots they received.
What is a blood clot and what causes them usually?
A blood clot is a thick, gelatinous drop of blood that can block circulation. Clots are formed in response to injuries and can also be caused by many diseases, including cancer and genetic disorders, certain medications and prolonged sitting or bed rest. Clots formed in the feet sometimes break and travel to the lungs or brain, where they can be fatal.
Can a vaccine cause blood clots?
Daniel Salmon, director of the Vaccine Safety Institute at John Hopkins University, said the vaccines have not been shown to cause blood clots.
Blood clots are common in the general population, and health officials suspect that reported cases in vaccine recipients are most likely coincidental and not related to vaccination.
Vaccine researcher Mark Slifka said, “There are many reasons for blood clotting, many risk factors, and many people who are at risk – and these are often people who are still being vaccinated. ” At the University of Oregon Health and Sciences.
From 300,000 to 600,000 rupees According to the Centers for Disease Control and Prevention, people in the United States develop blood clots in their lungs or veins in their legs or other parts of the body over a year.
Based on that data, a hematologist and professor of medicine at the University of North Carolina, Drs. According to Stephen Mol, there are about 1,000 to 2,000 blood clots in the US population every day.
“There are 253 million adults in the United States,” Drs. Mole said. “So, if 2.3 million people are vaccinated every day in the United States, it means that about 1 percent of the adult population gets vaccinated every day.”
Calculating further, he said that about 1 percent of 1,000 to 2,000 daily blood clots – 10 to 20 per day – would be in patients with the vaccine as part of normal background rates, not vaccine-related.
“Only if epidemiological data suggests that this rate is high will one begin to wonder about a causal relationship,” Dr. Mol said.
What can the current data on AstraZeneca vaccines tell us?
The director of the Vaccine Clinic at the University of North Carolina, Drs. David Wohl said he saw no evidence that any of Kovid’s vaccines led to his authorization of blood clots, also known as thrombosis, in large clinical trials.
But Dr. Wohl also said, “There are differences between tests and real life.”
The most widespread security results from AstraZeneca’s vaccine real-world rollout come from the UK, where 9.7 million doses of the vaccine Was given out through the previous month. UK data found that at least some clotting conditions, while extremely rare, were equally prevalent for those vaccinated with AstraZeneca vaccines compared to those receiving Pfizer products. But abnormally low platelet levels were more common in those who received the AstraZeneca vaccine.
Outside of testing, vaccines are given to broad masses. If the vaccine once comes into more general use, safety questions arise, questions should be investigated, Drs. Wohl said.
“We don’t want to ignore a sign that might indicate a major problem,” he said. “But at this point it is premature to think that AstraZeneca causes thrombosis.”
Do vaccines cause other bleeding disorders?
Other vaccines, especially given to children for measles, mumps, and rubella, are associated with temporarily lower levels of platelets, a blood component required for clotting.
Modern, low numbers of patients receiving Pfizer-BioNtech and AstraZeneca vaccines have decreased platelet levels. A doctor in Florida, a recipient died One suffered from cerebral hemorrhage when his platelet levels could not be restored, and others were hospitalized. US health officials have said the cases are being investigated, but have not reported the findings of those reviews and have not yet indicated that there is a link to the vaccines.
How will investigators determine if there is a link?
European Medical Agency Said on monday It was working with AstraZeneca and health officials to “examine all available data and the clinical circumstances surrounding specific cases.”
Officials have not detailed what the assessment will look like. But when assessing the possible relationship between a vaccine and serious side effects, investigators typically focus on estimating how often the chance of occurrence occurs in a group of people who question such medical problems. Will be.
This may mean that people look in the same group before getting vaccinated. It can also mean looking at a similar group of people. If the rate of these problems will be higher than expected in the comparative population in the vaccinated cohort, it is an indication that the safety issue may be real, or at least worth investigating.
Such investigations usually do not hamper definitively ascertaining whether the vaccine was the cause of death or a serious medical problem, as it cannot be determined in most cases. But investigators take into account the clinical history, such as when a person was treated for similar medical problems before being vaccinated.
Investigators also take into account factors that may make a group of people more likely to fall ill. Older people, who have been given priority in vaccination campaigns around the world, are at greater risk of developing blood clots than younger people.
The Ministry of Personal Health is also investigating, and health officials in those countries await the results of the autopsy. In Italy, moreover, authorities have seized vaccine supplements in the Piedmont area as part of an investigation into the teacher’s death over the weekend.
Can we expect an update on the investigation?
The World Health Organization advisory committee is scheduled to meet on Tuesday to discuss the vaccine. The safety committee of the European Medicine Agency will meet on Thursday.
Jennifer Nuzzo, an epidemiologist at the Center for Health Security at Johns Hopkins University, said she hopes authorities will provide regular updates on the status of investigations into the safety of the AstraZeneca vaccine – something that does not happen when there are safety issues. Investigated.
“I really wished there could be more continuous communication about what kind of analysis they are doing, even if they are interim – even if they are interim – transparency in the process to improve trust in the process To give, “Dr. Nazo said.
What has the company said about the fear of security?
AstraZeneca first publicly addressed security concerns a week after Austria Immunization vaccinated in a batch AstraZeneca vaccine. A company spokesperson said at the time that no serious vaccine side effects had been confirmed.
After Denmark on Thursday to stop all vaccinations with AstraZeneca’s product, the company made a statement and more explicitly defended the safety of its vaccines. The company said AstraZeneca’s safety data, a detachment of more than 10 million records, showed no evidence of risk of blood clotting problems in any demographic group or country.
On sunday, after Many more countries Announced plans to suspend its vaccination campaign, AstraZeneca Released a news With more people on the number of side effects reported and those vaccinated in clinical trials and in vaccination campaigns in Europe.
On Monday, a spokesperson for AstraZeneca said the company was “working with national health officials and European authorities and looks forward to their evaluation later this week.” (The company declined to name the spokesperson.)
Is there an example for vaccine safety?
Previous vaccine safety concerns have generally not been borne by the evidence, although there are exceptions. In 1999, the first vaccine against rotavirus infection that caused diarrhea in infants Market closed As it was found to increase the risk of intestinal obstruction.
But even disgruntled security concerns have eroded public confidence.
In 1998, the Food and Drug Administration approved a highly effective vaccine for Lyme disease, media reports and a class-action lawsuit fueled complaints from people who said they had developed arthritis after being vaccinated. In 2001, the FDA restructured a panel of experts to review vaccine safety data – clinical trials showed no difference in the frequency of long-term combined symptoms between the vaccine and placebo groups – and concluded that the vaccine market Should live on .
But by then, the public perception of the vaccine had gone too far: GlaxoSmithKline, the vaccine manufacturer to bring the vaccine to market in 2002, saw a steep decline in sales.
What is the status of the vaccine in the United States?
While more than 70 countries have authorized the vaccine, the United States has not. AstraZeneca has not yet applied for authorization to the Food and Drug Administration and is awaiting the results of its US trial in which more than 32,000 participants participated.
An announcement by AstraZeneca about those results could come soon: The data for that trial are being reviewed by an independent panel of experts, Drs. Francis Collins, Director of the National Institutes of Health, Told Reuters on Monday.
Strong safety and efficacy results from that test can go a long way in reassuring people about AstraZeneca’s vaccine, said Geoffrey Porges, an analyst at investment bank SVB Lerink.
“But the longer it hangs, the more people are going to be concerned, without a comprehensive review and without the US Phase 3 results,” Mr Porges said.