Young enjoy swine flu immunity

PUBLISHED : Monday, 06 September, 2010, 12:00am
UPDATED : Monday, 06 September, 2010, 12:00am

Almost half of the city's children aged five to 14 were exposed to swine flu during last year's outbreak and have consequently developed immunity against the virus that could protect them in the event of a further outbreak, a study has found.

The University of Hong Kong study, to be published in the journal Clinical Infectious Diseases next month, looked at 36,000 blood samples taken from donors between June last year and June this year with the help of the Red Cross. The samples were tested for their levels of swine flu antibodies, and the results broken down according to age groups.

Researchers found that among those aged five to 14, almost none had antibodies before the first wave of the swine flu outbreak in June last year. But by November, about 40 to 45 per cent had developed antibodies due to having been infected with a mild form of the virus that most would not even have noticed.

'Since most people develop antibodies after getting infected, we can infer from the study that nearly half of our children were infected in the first wave of the pandemic,' said Dr Benjamin Cowling, assistant professor at HKU's School of Public Health.

The percentage infected among other age groups was significantly lower than that in the children - about 15 per cent of those aged 15 to 19, 12 per cent of those between 20 and 29, and about 5 per cent among older age groups.

Assistant professor Dr Joseph Wu Tsz-kei, another researcher on the project, said the study could help the government know which age groups were most at risk, and help determine which should receive vaccination.

The findings were announced yesterday at an international conference on the control of flu at the Convention and Exhibition Centre.

Cowling said people should remain vigilant against swine flu, as the virus could mutate rendering people's immunity useless. The conference runs until tomorrow.