SEOUL, South Korea — The South Korean authorities are investigating the mysterious deaths of nine people after they had been vaccinated against seasonal influenza. And though officials said there was no link between the deaths and the vaccinations, there was worry that the cases could cause panic at a critical time for vaccination efforts.
The deaths happened over the past week, including five reported on Wednesday. Officials said that two of the deaths might have resulted from anaphylactic shock, a serious allergic reaction, but gave no further details.
The deaths are under investigation, but officials were quick to rule out the vaccines themselves — which they said were all from local drugmakers and not from lots for export — as the main cause. Given the scope of South Korea’s flu vaccination program, and the small number of other problems reported so far, some experts said that coincidence is more likely to involved.
Instead, officials vowed to step up a government flu-vaccination campaign to prevent the country’s health care system from being overloaded with flu patients amid the coronavirus pandemic — both viruses have similar symptoms of early infection, like fever and cough.
“We have not found a direct connection between these deaths and vaccines, or a relationship between the deaths and adverse effects reported after flu shots,” said Jung Eun-kyeong, commissioner of the Korea Disease Control and Prevention Agency. “We don’t think that the situation calls for the suspending of the inoculation program.”
Ms. Jung convened a special news conference on Wednesday after the rapid series of deaths, starting with a teenager who died on Friday, grabbed headlines in South Korea. But with autopsies likely to take days, public anxiety is running high in a country where anti-vaccine sentiment has flared before.
South Korea, and many other countries, have seen annual flu inoculation programs as critical to efforts to also deal with the coronavirus, especially for children, the elderly, pregnant women and medical personnel. Officials unveiled plans to procure 20 percent more flu vaccines for this winter than last year to inoculate up to 30 million people, more than half the country’s population.
But the campaign made headlines last month when it was discovered that some vaccines supplied by a local company, which needed to be refrigerated at all times, had been exposed to room temperature while being transported. A recall was ordered and officials said about 2,300 people had received doses from the faulty batch, which was meant mainly for young children and teenagers.
Still, officials said that alone should not have rendered the vaccines dangerous. According to the Centers for Disease Control and Prevention, the concern about lack of temperature control is that it can render the vaccines ineffective, rather than toxic.
Then, earlier this month, 615,000 doses of a flu vaccine shipped by another company were also recalled after some of them were found to contain white particles, which the government described as being a harmless protein. Almost 18,000 people had received doses before they were recalled.
No serious harm had been reported from either those lots, though dozens of people who received those doses reported fevers or other minor complaints — which are common reactions to flu shots, officials said. None of the nine people reported dead received vaccines from those that had been recalled, they added.
After suspending the vaccination program for teenagers for three weeks, it resumed on Oct. 13. Three days later, a 17-year-old boy in Incheon, just west of Seoul, died after receiving his shot. On Tuesday, a 77-year-old woman was found dead at her home in Gochang, south of Seoul, after being vaccinated a day earlier. On the same day, an 82-year-old man who had also been inoculated died in the central city of Daejeon.
Four of the five people who died on Wednesday ranged in age from 53 to 89. Information about the two other people who died, one on Tuesday and one on Wednesday, has not been released.
The nine who died, all of whom had received flu shots in the past, received vaccines supplied by several different local drugmakers, officials said.
“Since most people who got flu shots with the same vaccines reported no major problems, we concluded that those vaccines do not contain toxic materials,” said Kim Joong-gon, a professor of medicine at Seoul National University who led a team of investigators. “We concluded that we can exclude the vaccine as a problem.”
In general, flu vaccines have a good safety record. In the United States, the Centers for Disease Control and Prevention say that the body of scientific evidence over decades “overwhelmingly” supports their safety.
Specifically in South Korea, officials said that since 2009, 25 people in South Korea had died after receiving flu vaccinations, but that only one of the deaths was tied to the process.
Nearly 13 million South Koreans have received flu shots so far this year, 8.3 million of them for free as part of the government program. There have been complaints about minor reactions to shots, but those are normal every flu season. And Ms. Jung said Wednesday that some of the complaints were likely to have been influenced by media coverage of the recalls.
The anxiety over flu shots could also undermine public trust in an eventual coronavirus vaccine, which is already faltering as countries race to get their candidates approved. In a survey this month of 2,500 people in Gyeonggi-do, a populous province surrounding the South Korean capital of Seoul, 62 percent of respondents said they would not get vaccinated against the coronavirus until after the vaccine was proved to be completely safe.
Many scientists have expressed concern about the speed with which coronavirus vaccines are being developed. But getting a vaccine approved is only one hurdle. Managing public perception is another, especially if there are concerns about the vaccine being mishandled during transportation and storage.
Most vaccines have to be kept at low temperatures from the time they are manufactured to the time they are administered to prevent them from spoiling — what the industry calls a “cold chain.” The flu vaccine, for example, needs to stay refrigerated, at between 2 and 8 degrees Celsius.
That could complicate the distribution of a coronavirus vaccine. A number of the leading candidates under development would need to be kept at temperatures as low as minus 80 degrees Celsius (minus 112 degrees Fahrenheit).
In the United States, transportation and warehouse companies are scrambling to build “freezer farms.” Airlines are fitting their planes with freezers, and glass vial makers are inventing methods to make vials that do not crack from very cold temperatures. Courier services like UPS and FedEx are making dry ice.
But cold facilities are lacking in other parts of the world, including Central America, rural India and Southeast Asia, which experts say could hinder mass immunization.
Typically, multiple reports of adverse reactions from vaccines are investigated by a country’s drug regulator in an attempt to determine the frequency of such events and whether there are causal links. While these investigations are underway, countries can choose to continue the vaccination program if the benefits are considered to outweigh the risks.
Choe Sang-Hun reported from Seoul, South Korea, and Sui-Lee Wee from Singapore.