Wrong WHO prediction leads to flu vaccine mismatch in Hong Kong
Wrong strains are targeted following inaccurate influenza prediction by world health watchdog
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.
Every February, the WHO announces its prediction of the most widespread flu in the coming flu season. Pharmaceutical firms will then produce relevant vaccines and launch them on the market around September.
As the winter surge begins around December, there is a gap of eight months between the prediction and the start of the actual flu season. Yuen said there was a possibility the virus could mutate during this period.
Dr Tse Hung-hing, a former president of the Hong Kong Medical Association, said he had noticed an increased number of flu patients in his clinic compared to last year.
He was disappointed with the mismatch in vaccines but understood the limitations involved.
"It is just a prediction [of the strain] and there isn't a completely accurate one," said Tse. "Vaccination is still the best preventive measure against flu."
