The World Health Organisation wrongly predicted the most prevalent strains of influenza during the current flu season, with a resultant reduction in protection against the virus, the Department of Health has revealed.
The department said samples collected this season showed a prevalence of A sub-type H3N2, which differs from that targeted by vaccines the WHO recommended for use in the northern hemisphere this winter.
Other countries, including the United States and Canada, reported the same flu strain as Hong Kong.
However, the prevalent H3N2 strain in the northern hemisphere matches those WHO- recommended vaccines used in the southern half of the globe.
The Centre for Health Protection followed the WHO advice and made the same flu vaccines recommendation last July.
The CHP noted a slight increase in severe flu cases in the first two weeks of the year, with 10 flu-related deaths among 41 adult patients admitted to intensive care wards in public and private hospitals. Of those cases, 36 were infected with H3N2 and five had recently received flu vaccines.
The figure was higher than between January 3 and 15 last year, when there were nine deaths among 25 severe flu cases.
Yuen Kwok-yung, professor of infectious diseases at the University of Hong Kong, said a mismatch in flu vaccines would reduce the protection rate against H3N2 by about half.
"The protection rate drops from around 80 per cent to 30 per cent," said Yuen. "However, the vaccine still protects people from H1N1 and influenza B very well."
The actual flu strains turn out to be different from the WHO's prediction about every three to six years, he added.
Yuen advised that young children, elderly people, pregnant women and people with chronic diseases should still take the flu vaccine, as these groups were more likely to develop severe complications if infected.
This article appeared in the South China Morning Post print edition as Vaccine mismatch leads to reduction in flu prot
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