Despite concerns over blood clotting reports, there is no reason to hesitate to get the AstraZeneca’s Covid-19 vaccine, an expert said.
The AZ vaccine’s risk of causing blood clots has been exaggerated due to inaccurate information, he said.
Na Sang-hoon, a professor at the Cardiology Department of the Seoul National University Hospital, said in a medical seminar that the recent controversy over blood clots related to the AZ Covid-19 vaccine was unnecessary because the facts were not properly identified or data was inaccurately cited.
Na said people needed to use accurate terms first. Thrombosis recognized to be associated with the AZ vaccine is “unusual blood clots with low platelets,” and its incidence is rare.
However, as news reports used the term “blood clots” with the broadest meaning, people have misunderstood thrombosis as a side effect with a high incidence, Na said.
The European Medicines Agency said on March 18 that blood clots’ causal link with the AZ vaccine was not proven. Earlier, the EMA excluded arterial thrombosis, which causes stroke and myocardial infarction, from the possibility of the causal link with the AZ vaccine.
In the second report on March 31, the EMA confirmed that venous thrombosis was unrelated to the AZ vaccine. Cases of unusual blood clots with low platelets, including cerebral venous sinus thrombosis (CVST), require further, and there is no definitive causal link, the EMA said.
In the final report on April 7, the EMA concluded that unusual blood clots with low blood platelets should be listed as very rare side effects of the AZ vaccine.
As of April 19, however, there was no report of such rare thrombosis with thrombocytopenia, and one reported blood clots in unusual sites.
The AZ vaccine and other vaccines such as the Janssen vaccine, Sputnik V, the Pfizer vaccine, and the Moderna vaccine reported cases linked to rare thrombosis.
However, the incidence is very rare. As of April 19, Europe reported 3.5-6.5 rare thrombosis cases per 1 million AZ vaccine shots, U.S., one or two cases per 1 million Janssen shots, and Argentina, 1.3 cases per 1 million Sputnik V shots. The Pfizer vaccine reported 0.6 cases per 1 million shots in Europe, and the Moderna vaccine, 1.25 cases per 1 million jabs around the world, including the U.S.
In Korea, no rare thrombosis case has been reported since the vaccine rollout. Assuming from the difference in the incidence of venous thrombosis related to pregnancy and childbirth, the incidence is expected to be at about 0.7 to 1.3 per 1 million shots, Na said.
“Venous thrombosis risk increases with a probability of 1 in 10,000 even when flying longer than 10 hours, and the risk also rises with a probability of more than 4 in 10,000 even after taking contraceptives,” Na said.
The risk of dying from Covid-19 without vaccination is four to 10 times higher than the risk of dying from rare thrombosis after receiving the AZ vaccine, Na went on to say.
If the entire Korean population had received the AZ vaccine for the past six months, the total Covid-19 cases would have gone down from 100,000 to 20,000, and deaths from 1,700 to 340, assuming that the vaccine was 80 percent effective, he said.
“Four people could die of rare thrombosis after getting the AZ jab, while the vaccination can prevent more than 1,300 Covid-19 deaths,” Na said. “Is it right to give up vaccination which can save over 1,300 people just because it would cause four more deaths?”
Every Covid-19 vaccine can cause a very rare serious adverse reaction, but such incidence is lower than those of most drugs currently available, Na explained.
“If you have the benefits of preventing the risk of Covid-19, which is still raging around the world, the best thing you can do at the moment is to get any vaccine and try to prepare for rare but serious side effects.”