It was evaluated that there is a causal relationship between the COVID-19 vaccination and the occurrence of some abnormal uterine bleeding.
However, it confirmed the risk of frequent menstruation ( shorter menstrual cycle than usual) and bleeding within a relatively short period of time, and no relationship with menstruation or rare menstruation was confirmed.
The COVID-19 Vaccine Safety Committee of the Korea Medical Center released the results of the third analysis of abnormal reactions after the COVID-19 vaccination on the 11th.
(Picture from Unsplash)
The Safety Commission was launched in November last year with the aim of evaluating the scientific causality of abnormal reactions after COVID-19 vaccination at the request of the Korea Centers for Disease Control and Prevention, and has announced the results of two studies.
The committee conducted an analysis of the relationship between the COVID-19 vaccine and the risk of abnormal uterine bleeding related to frequent menstruation and bleeding within 120 days of the first vaccination date among the first vaccination patients from February 26 to October 31, 2021.
Through the Self-Controlled Patient Group Study (SCCS), the risk interval (excluding the risk interval within the observation period) was compared with the risk interval of 30 days or less after vaccination, which is believed to be due to the vaccine in case of abnormal uterine bleeding.
As a result, 108,818 patients first experienced frequent menstrual and bleeding-related abnormal uterine bleeding within 120 days of vaccination, and the risk of abnormal uterine bleeding within 30 days after vaccination was 1.42 times higher than that of the control section.
The committee explained, "As a result of synthesizing the scientific evidence to date, including the results of this study and literature review, it is evaluated as an acceptable stage to accept that there is a causal relationship between the COVID-19 vaccine and abnormal uterine bleeding.
He added, "However, it confirmed the risk of abnormal uterine bleeding related to frequent menstruation and bleeding within a relatively short risk section, and cannot explain the relationship with abnormal uterine bleeding such as amenorrhea and rare menstruation."
In addition, the committee's position is that additional studies are needed on the population who have chronic abnormal uterine bleeding after vaccination, as the subjects of the study include both temporary abnormal uterine bleeding but recovering later and continuous symptoms after abnormal uterine bleeding.
The incidence ratio and association analysis of cerebral venous sinus thrombosis, in which blood clots (spaces in venous vessels) in the brain, also confirmed an increase in incidence. Cerebral venous sinus thrombosis can cause a stroke because blood cannot escape from the brain if it persists for a long time.
In particular, in the small group analysis, increased risk was observed in the age group of 30 to 49, 50 to 64 years old, and women. However, the committee said, "The risk of occurrence increased statistically significantly after vaccination, but these results need to be interpreted carefully in consideration of research limitations such as diagnostic accuracy."
He also added, "In order to produce evidence free from these limitations, research using a registry (registrant) that systematically collected patient data confirmed in Korea should be conducted."
In addition, deep arrhythmia thrombosis, in which blood clots due to blocked leg veins, did not show an increase in the incidence of the entire vaccine in the composite outcome, which collected all related diseases, when comparing the risk period and the control period after inoculation.
However, most experts agreed that a slight increase in the overall binding index and the consistent incidence of risk periods compared to the post-vaccination control period of individual diseases was detected in the Pfizer vaccine, and a detailed analysis was required.
In addition, since this is inconsistent with overseas research results and there is a possibility of overdiagnosis due to concerns about abnormal reactions, a close epidemiological evaluation of deep vein thrombosis and pulmonary embolism will be conducted after Pfizer vaccination in the future, the committee added.
Park Byung-joo, chairman of the safety committee, stressed, "Although some diseases have been confirmed to be related to vaccination, careful interpretation and further research should be followed considering limitations on the diagnostic accuracy of the data used in the study."
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