Vaccine no match for rogue flu strain
A rogue flu strain has surfaced in New Zealand, infecting even those who have had their annual vaccination.
Most flu sufferers this year have had the H1N1 influenza A strain, or swine flu, against which the latest vaccine offers good protection.
But about 8 per cent of cases have involved a new strain that had changed quite a lot, National Influenza Centre director Sue Huang said yesterday, and there had been a reported surge in immunised people catching flu.
The problem was caused by a different strain of the H3N2 influenza A virus surfacing unexpectedly this year, she said.
The flu vaccine had three components - two influenza A strains and one B strain - which were selected each year to match the strains predicted to strike the following winter.
However, the H3N2 flu virus, an A/Texas/50/2012 strain, had drifted quite a lot by the time it arrived in New Zealand, she said.
That meant those who contracted it had little or no immunity to it.
It was fortunate the rogue strain had affected only a small percentage of this year's sufferers, so not many vaccinated people had been at risk, she said.
"That is lucky, because we don't want to be in that situation where it's the predominant strain."
New Zealand had been more fortunate than New South Wales, where the rogue strain had predominated, causing a large outbreak because the annual vaccine had been of limited use, she said.
It had forced public health officials in both countries to make big changes to next year's vaccine.
Among those succumbing to flu in the past couple of weeks have been half the New Zealand indoor cricket team, who have been playing in the World Cup at the Hutt Indoor Sports Centre.
It was not known how many had been vaccinated but some of the team, including Lower Hutt resident Nick Ward, were clearly having to continue playing while still ill.
Greater Wellington medical officer of health Jill McKenzie said: "Anecdotally, we did hear about people who did have flu-like symptoms and who had been vaccinated, and it was potentially a few more that we might have had in previous years."
None of the four reported flu-related deaths in Auckland this year were blamed on the rogue flu strain, she said.
Huang said flu viruses frequently underwent changes, which posed a challenge for public health officials because vaccine formulas had to be chosen about six months in advance so that drug companies could manufacture them.
"We want to be as close as possible, so it's always a bit of a struggle in terms of timing."
This year's rogue strains have forced the biggest changes in vaccine formula for several years.
Each year, the Australian Influenza Vaccine Committee, which includes Huang, meets to decide the composition of the vaccine for the following winter season for New Zealand, Australia and South Africa.
It announced last Friday the recommended formula for next year would include the same H1N1 strain as this year, but would have an A/Switzerland/9715293/2013 virus, similar to H3N2, to combat the newly morphed strain.
Despite the problems caused by the rogue strain, this year's flu levels have been the third-lowest since 1992.
The annual influenza surveillance report, made public in May, showed that last year there was the highest level yet of vaccination coverage, with 67.4 per cent of people aged 65 and older getting a flu jab.
Have you been struck down by the flu this year? Had you been vaccinated? Leave a comment to share your experience.
The Dominion Post