South Korean public health authorities are investigating reports of suspected adverse events among people who received a COVID-19 vaccine.

As of midnight Tuesday, 87,428 people in Korea had received a dose of a COVID-19 vaccine -- around 85,000 of them being the AstraZeneca vaccine and the rest Pfizer vaccine -- with 209 of them reporting “adverse reactions.”

The vast majority -- 204 cases -- of the reported events were known, mild side effects such as headaches, low-grade fever and nausea. Three were of symptoms akin to anaphylaxis, an acute and potentially life-threatening allergic reaction that manifests typically within 15 to 30 minutes following vaccination. Two involved the death of chronically ill patients at nursing hospitals.

One of the patients who died was a man in his 50s at a nursing hospital in Goyang, Gyeonggi Province, with “multiple medical conditions” including Alzheimer’s, Parkinson’s and diabetes.

The city office said the man was given emergency treatment after developing shortness of breath and other serious symptoms before he was pronounced dead at 7:15 a.m. Wednesday at the hospital. He was inoculated with the AstraZeneca vaccine at 9:30 a.m. the previous day.

The other death was a man in his early 60s at a nursing hospital in Pyeongtaek, Gyeonggi Province. The city office said he died at around 10 a.m. Wednesday, four days after getting an AstraZeneca vaccine.

Whether the vaccines are related to any of these events is being investigated, Korea Disease Control and Prevention Agency Commissioner Jung Eun-kyeong said in a news briefing Wednesday afternoon.

“Reports of adverse reactions after vaccination do not mean they were truly caused by a vaccine,” she said.

“Over 200 million doses of the vaccines have been administered globally, and although several deaths were reported among the vaccine takers, none of them was found to be a result of a vaccine.”

She added that the agency was activating a surveillance system to monitor and look into cases of side effects for possible cause-and-effect relationships.

Experts worry such events being reported may boost skepticism among Koreans.

In a phone interview Wednesday afternoon, virologist Dr. Paik Soon-young of Catholic University of Korea said data from countries where mass vaccinations are well underway “give further assurance in the safety of COVID-19 vaccines.”

Data from early February released by the UK’s Medicines and Healthcare products Regulatory Agency showed 22,820 reports of suspected side effects out of over 10 million doses of Pfizer and AstraZeneca vaccines given there. This translates to a reporting rate of 3 in 1,000 doses of vaccine administered.

The US Centers for Disease Control and Prevention’s data published last week shows out of over 13 million doses of Pfizer and Moderna vaccines administered there, there were 6,994 reports of suspected side effects after vaccination. Over 90 percent of the reports were classified as not serious.

In Tuesday’s statement, the Korean Society of Infectious Diseases said all of the current vaccines approved for use here meet the standards of both safety and effectiveness.

“The reported rate of side effects to COVID-19 vaccines is similar to that of existing vaccines,” the society said.

Korea kicked off its vaccination campaign for at-risk groups at long-term care facilities and workers at COVID-19 hospitals on Friday.

By Kim Arin (arin@heraldcorp.com)