[Issue! Q&A] "50% Probability of Thrombus Dissolution Within 1 Week... Setback in Herd Immunity"

Four Key Issues in Vaccine Chaos... Experts "Need to Consider Using Pfizer Vaccine for Under 60 Instead of Over 75"

[Asia Economy Reporter Seo So-jeong] The European Medicines Agency (EMA) has acknowledged a possible link between the AstraZeneca COVID-19 vaccine and rare blood clotting disorders, causing a halt in South Korea's vaccination plans. The government, which intended to continue vaccinations citing that the benefits far outweigh the side effects, has postponed vaccinations for school and childcare workers as well as workers in vulnerable facilities, disrupting the second-quarter schedule.

Among the 18,088,000 vaccine doses to be introduced in the first half of the year, 10,674,000 doses are AstraZeneca vaccines, leaving the government in a dilemma as it has not prepared alternative vaccines. The government plans to decide its official stance this weekend after expert consultations and discussions by the Vaccination Expert Committee regarding the EMA's investigation results.

Q. Is it safe to receive the AstraZeneca vaccine?

A. A case was reported yesterday where a woman in her 20s, vaccinated with the AstraZeneca vaccine as a healthcare worker, was found to have blood clots in her leg and lungs. Earlier, a man in his 20s, a first responder to COVID-19, was diagnosed with cerebral venous sinus thrombosis (CVST). In February, a patient in their 60s at a nursing hospital died eight days after vaccination, with blood clots found during an autopsy. Professor Jeong Ki-seok of Hallym University Respiratory Medicine (former head of the Korea Disease Control and Prevention Agency) stated, "With about one million vaccinations administered domestically and three cases reported, causality cannot be ignored," and emphasized, "Although late, alternatives must be sought now."

Q. How dangerous is thrombosis?

A. The EMA stated that very rare cases of cerebral venous sinus thrombosis (CVST) and disseminated intravascular coagulation (DIC) may occur in AstraZeneca vaccine recipients. These conditions involve increased blood clots and decreased platelets, with most thrombosis cases occurring in women under 55 years old based on overseas data. A man in his 20s in South Korea complained of a headache described as feeling like being hit on the head with a hammer, and when his condition did not improve, he was diagnosed with CVST through magnetic resonance imaging (MRI) and computed tomography (CT) scans.

CVST is a condition where blood clots form in the cerebral venous sinuses, causing brain dysfunction. It is accompanied by severe headaches and, if intracranial pressure rises, blurred vision may occur. In typical venous thrombosis cases, anticoagulants can dissolve clots in about 50% of patients within one week, and over 80-90% of clots dissolve after three months. However, there are dangerous cases. Professor Cheon Eun-mi of Ewha Mokdong Hospital explained, "Blood clots, which are essentially 'masses of blood,' can adhere to various organs causing circulatory disorders," adding, "Especially if the pulmonary artery is blocked causing pulmonary embolism, it can lead to respiratory distress and sudden death."

Lee Sang-hoon, president of the Korean Dental Association, is receiving the AstraZeneca COVID-19 vaccine at the Mapo-gu Public Health Center in Seoul on the 2nd. Photo by Hyunmin Kim kimhyun81@

Q. When will other vaccines arrive?

A. The government plans to additionally import Janssen, Moderna, and Novavax vaccines in the second quarter, but the exact quantities have not yet been confirmed. Novavax, for which 20 million doses have been secured, is facing raw material supply issues and has not yet been approved. The government is actively considering export restrictions on vaccines produced domestically by SK Bioscience.

The Korea Disease Control and Prevention Agency stated that the Covax AstraZeneca vaccine produced domestically is listed on the World Health Organization (WHO) Emergency Use Listing (EUL), so quality data review and package inserts are required in Europe, but negotiations are underway to allow its use domestically without export to Europe. However, with the AstraZeneca blood clot controversy unresolved, trust in the vaccine is declining, leaving no suitable alternatives.

Q. Is it possible to achieve herd immunity by November?

A. A total of 142,202 people have had their vaccinations postponed, including 38,771 under the age of 60 whose vaccinations have been deferred. The government plans to complete first-dose vaccinations for 70% of the entire population by September and achieve herd immunity by November. According to this plan, the first-dose vaccination target is 20%, which requires all second-quarter vaccination targets to be vaccinated. However, with the vaccination plan for those under 60 postponed due to the blood clot controversy, the timeline for herd immunity is inevitably delayed.

Professor Jeong Ki-seok stated, "We need to ask for public understanding and consider as an alternative administering the Pfizer vaccine, originally intended for those over 75, to those under 60," adding, "There may be refusal for the second dose among those who received the first AstraZeneca dose, so efforts to improve vaccine trust must be actively pursued."