Flu vaccines may be lulling people into a false sense of security, with a new study showing they cannot always protect against fast-changing strains of the virus.
Hospital doctors compared 100 people, some of whom received the 2012 vaccine and others who did not, in a New Zealand Medical Journal article released today. All were selected after being admitted to hospital with a particular flu strain, H3N2.
Those who had been vaccinated stayed in hospital just as long, and were admitted to the intensive care unit just as frequently, as those who were not, study co-author Lutz Beckert said.
However, he emphasised the Christchurch Hospital study did not mean people should forgo their yearly flu vaccine.
But people should be aware flu could strike even after the jab. "Our vaccines aren't perfect."
H3N2 was New Zealand's most common flu strain in 2012, and caused more severe complications and higher deathrates than other types.
Beckert, a respiratory physician and University of Otago associate professor, said the 2012 vaccine contained an "inactivated" or killed version of the H3N2 virus. The Government spent more than $18.6 million targeting high-risk groups that year, vaccinating more than 1 million people.
"Yet we were busy that winter admitting people with this strain, despite the fact they should have been vaccinated against it."
Vaccines sensitise the immune system to specific targets on the outside of the deadened flu virus, with strains selected by scientists months in advance.
When the real flu arrives, the body reacts straight away, killing the virus.
But those targets could mutate quickly into ones the vaccinated person's immune system might no longer recognise, Beckert said. "When you create a vaccine you're trying to predict the future . . . They got it right, in the sense the H3N2 virus arrived in New Zealand, but it had already mutated."
Wellington GP Cathy Stephenson said that, despite information given by doctors and nurses, there was still widespread misunderstanding about immunisation.
"There's a common perception that, if you get the flu jab, you can't get the flu," the Victoria University Student Health Service practitioner said. "We certainly warn people it's not bulletproof - and that if you get symptoms of the flu, it's really important that you take it seriously and don't brush it off as a cold."
Fellow Wellington doctor Lesley Rothwell, of City GPs, said the immunologists behind the flu vaccine often got it right, as they did this year in anticipating the H1N1 strain would appear. "It's the best we have available."
With 80 the average age of the participants, the study supported recent research showing that the effectiveness of the flu vaccine for the elderly was only 8 per cent, co-author Lance Jennings said. In healthy adults, where the strain matches the vaccine, immunisation is on average 70 per cent effective at preventing the illness.
Jennings suggested the Government consider alternate strategies, such as Britain's vaccination programme for children aged 2 to 16, a group thought to commonly spread the disease. Almost 1.2 million Kiwis received the flu injection this winter.
A second study in today's Medical Journal shows New Zealanders' belief in their invulnerability is frequently behind decisions not to get a flu jab.
The study asked more than 2600 people about their immunisation choices. On average, more than 340 Kiwis die each year from flu-associated deaths, with costs for related hospital care spiking to $30 million in 2009.
Yet two-thirds of the survey participants - mostly young adults - said they did not get the vaccine. More than one in five said their reason was because they never got the flu. Others believed they were healthy enough not to be struck down, going against research showing certain strains were more common in young, healthy people.
Other reasons for not being vaccinated included a distrust of vaccines.
The study comes a day after supplement company Health 2000 was forced to clarify its claims that flu vaccines were an "onslaught of mercury and toxins". It acknowledged the NZ immunisation does not contain mercury.
- The Dominion Post