WHO's dominant flu strain right for Hong Kong 'only 60pc of time'
University researchers say new vaccine could take the guesswork out of treating influenza B
The World Health Organisation tries to predict the strain of influenza B that will dominate cases around the world every year - with accuracy of no better than 60 per cent for Hong Kong in recent years, a Chinese University study has found.
Manufacturers produce vaccines based on the WHO's predictions. But when the forecasts are wrong, those medications offer no protection against the more dominant B strain. But the vaccines do provide almost complete protection against the more common influenza A.
The study, released yesterday, suggests taking the guesswork out of this process by using a new type of medication known as a "quadrivalent" vaccine, currently being developed by overseas manufacturers.
They provide protection against the four most common strains of influenza virus - two types of influenza A (H1N1 and H3N2) and two of influenza B (Yamagata and Victoria).
The current "trivalent" vaccine protects against the strain predicted by the WHO. "The trivalent influenza vaccine seems to be less than ideal in preventing influenza B," said Professor Paul Chan Kay-sheung, chairman of the university's microbiology department, who led the study.
"We expect that the quadrivalent vaccine will be a big help to influenza control in Hong Kong, especially in reducing the chance of infection in schoolchildren."
Chan hopes the new vaccine will be available in Hong Kong by the end of this year.
The study looked at the years 2000 to 2010, excepting 2009 because of a major swine flu outbreak that year.
In six of the 10 years, or 60 per cent of the time, Hong Kong's dominant strain of influenza B matched the WHO's prediction.
But for the six years with a marked dominance - with more than 80 per cent of cases being one of the influenza B strains - only two of these years had matching vaccines.
That low success rate, Chan said, may be due to Hong Kong's location near areas where new virus variants commonly appear.
Of the 5,210 influenza patients admitted to Prince of Wales Hospital in those 10 years, 24 per cent had influenza B.
Responding to the study, a Department of Health spokesperson said the vaccines on hand this flu season were appropriate for the strains of virus that are appearing.