Some recipients of Johnson & Johnson’s COVID-19 vaccine were not given any warnings of potential rare blood clots as the rollout began last week, The Korea Herald has found.

People who had received the Janssen vaccine during the early days of its rollout say no warnings or information was given about the rare but serious side effect. The blood clotting condition, termed thrombosis with thrombocytopenia syndrome, or TTS, is associated with two adenovirus-based vaccines developed by Johnson & Johnson and AstraZeneca.

The Korea Herald spoke to at least two health care workers in charge of administering the vaccines and five recipients over the weekend.

A man from Seoul who received the Janssen vaccine on Thursday, on the first day of its rollout, told The Korea Herald that he “heard nothing about the risk of blood clots.”

“The fact sheet they handed to me listed cold-like symptoms such as fever and allergic reactions as possible side effects following vaccination. But there was nothing about blood clots,” he said. He said he was among the very first recipients of the shot at a clinic in the city’s eastern Seong-dong district.

Another recipient, 30, who was also inoculated with the shot on the same day in Gangnam, said neither the text message nor the flyer he received contained “any mention of blood clots.” “I wasn’t told to look for signs or symptoms of blood clots,” he said.

Dr. Choi Seung-jun, the head of a medical association that serves Yongsan district in central Seoul, said the latest guidelines he had on the Johnson & Johnson vaccine did not include advice about the blood clot risks.

“There haven’t been formal instructions from the top regarding this specific side effect of the Johnson & Johnson vaccine -- not yet, anyway,” he said. “But doctors participating in the vaccination campaign should be aware of the risks associated with each vaccine regardless.”

Another primary care physician, who asked to remain anonymous, said, “Health professionals are having to teach themselves about these safety signals and rare side effects.”

The physician said such information should be relayed to front-line vaccinators promptly so that when patients present with potential symptoms, they won’t be overlooked. “These are very rare conditions that even doctors aren’t really familiar with.”

Dr. Kim Woo-joo, an infectious disease professor at Korea University, said as symptoms of the side effects are nonspecific and varying, “educating people about the signs and symptoms to look out were vital in a safe vaccination program, especially as early diagnosis and treatment tend to result in better outcomes.”

The known symptoms of the rare blood clot include blurred vision, lasting headache or abdominal pain, shortness of breath and dizziness which can occur between four to 30 days after vaccination. 

In response to a media inquiry from The Korea Herald, a Korea Disease Control and Prevention Agency official said: “Although TTS is very rare, the agency is providing the recipients and care providers with a fact sheet that includes necessary information on how to recognize and respond to this disorder.” 

But photos of the fact sheets taken by the vaccine recipients seen by The Korea Herald did not list the blood clots.

Park Young-joon, who is leading the Korea Disease Control and Prevention Agency’s COVID-19 vaccine adverse event monitoring team, said the team’s survey of about 10,000 people who received the Johnson & Johnson vaccine found no complaints of serious side effects.

“Most side effects were mild and short-lasting,” he said.

Meanwhile in Daegu, a 38-year-old with an underlying blood disorder died Sunday, three days following Johnson & Johnson vaccination, Park said. He did not specify the type of blood disorder. Post-mortem examinations were underway but no clear link to the vaccine has been established at the moment, he said.

By Kim Arin (arin@heraldcorp.com)