More than 11 percent of Koreans were immune to the H1N1 virus even before it began spreading this year, a study finds. Experts attribute the immunity to a similar flu that swept the nation before 1956.
Twenty-three out of 200 Koreans tested positive for antibodies against the virus, according to the study submitted Monday to Democratic Party lawmaker Jeon Hyun-heui by the Korea Center for Disease Control and Prevention.
The KCDC research was done in August and September with serum collected for a nutrition study in 2008, so the samples were not exposed to the strain of flu virus that began spreading rapidly in May.
Dr. Kim Woo-joo of Korea University Hospital said the current H1N1 virus is the same type of virus that caused the Spanish Flu pandemic that spread throughout the world, including Korea, between 1918 and 1956. "People born before 1956 who contracted the Spanish Flu or were vaccinated for it could have developed antibodies," he said.
Although most of the people who have died from the current flu outbreak were over 65 years old, 88 percent of the 27,006 Koreans infected with the virus are 30 years old or younger. Those over 60 account for just 1.7 percent of the infections.
"The U.S. Centers for Disease Control conducted a test using blood samples collected before the outbreak began in May and found that 33 percent of Americans aged 52 or older were found to be immune to the H1N1 virus," Dr. Kim said.
Kang Chun, a director of the influenza virus team at the KCDC, said, "The latest experiment involved only few samples, and we need to conduct a broader test using more blood samples by age groups."