Besides the Covid-19 vaccine, do other vaccines cause blood clots?
Recently, the news that AstraZeneca admitted that the Covid-19 vaccine can cause blood clots has made many people confused, worried and wondering whether other vaccines can cause this side effect?
To learn more about this issue, reporters from Health and Life Newspaper had an interview with Associate Professor, Dr. Pham Quang Thai - Deputy Head of the Department of Infectious Disease Control, National Institute of Hygiene and Epidemiology.
Causes of blood clots after Covid-19 AstraZeneca vaccine injection
Reporter: Associate Professor, Dr. Pham Quang Thai, what is the cause of blood clots after receiving the AstraZeneca Covid-19 vaccine?

Assoc. Prof. Dr. Pham Quang Thai - Deputy Head of Department of Infectious Disease Control, National Institute of Hygiene and Epidemiology.
Assoc. Prof. Dr. Pham Quang Thai: Blood clots often occur in people with thrombophilia, a problem with the immune response, the body creates antibodies that can stick to one of the body's natural proteins. This protein is called platelet factor 4 (PF4). In fact, when people have an infection, many people create antibodies that can stick to PF4 as part of the immune response, but these antibodies are often weakly sticky.
In people who get blood clots from vaccination, the antibodies that form can stick very tightly to PF4, forming larger structures called “immune complexes.” These complexes stick together and activate platelets. Normally, platelets float in the blood in an inactive state, but once activated, they form a “net” that forms clots.
Do blood clots occur with other vaccines?
Reporter: So does this side effect occur with other common vaccines, Associate Professor, Doctor?
Assoc. Prof. Dr. Pham Quang Thai: This phenomenon can also occur when there is an antigen-antibody reaction. Thus, not only the Covid-19 vaccine, thrombotic side effects can occur with other vaccines or in cases of infection.
In fact, there was a case of a baby born with numerous blood clots in the lungs due to the mother having chickenpox during pregnancy. The baby died about 30 minutes after birth.
However, this rate is very low, even in European communities it is very rare (European communities have a high rate of natural thrombosis (up to 10/million/21 days) compared to other communities, especially when compared to Asia where this rate is extremely low (less than 1/million/21 days).

The reported thrombotic events occurred essentially only within 28 days of vaccination.
Who is susceptible to blood clots after vaccination?
Reporter: Who is at high risk of developing blood clots after vaccination, expert?
Assoc. Prof. Dr. Pham Quang Thai:In healthy people, the rate of blood clots after vaccination is very low. This risk may be higher in people with a history of blood clotting disorders. These cases are carefully examined and monitored by doctors before, during and after the vaccination process to ensure safety.
Should we be concerned about blood clots after getting the Astrazeneca Covid-19 vaccine 2-3 years ago?
Reporter: Expert, up to now, after the majority of people were vaccinated with the Astrazeneca Covid-19 vaccine 2-3 years ago, can this side effect still occur?
Assoc. Prof. Dr. Pham Quang Thai:The reported thrombosis issues typically only occur within 28 days of vaccination and mostly after the first dose of the vaccine. Therefore, there is no need to worry about side effects that lead to blood clots. Currently, many people go to medical facilities to perform unnecessary blood clotting tests, if only because of concerns about side effects of the Covid-19 vaccine.
People need to find out official information, avoid worrying, panic... Information that Covid-19 vaccine can cause blood clots is not a new or strange issue. However, taking advantage of this opportunity, many "anti-vaccine" groups have posted false information on many social media channels, so people need to be alert, avoid unnecessary misunderstandings.
PV: Thank you, Associate Professor, Dr.