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Call to vaccinate before next flu pandemic

HINI influenza vaccine

We should learn from our experience of swine flu and pre-empt the next influenza virus to jump from animals into humans, say some(Source: Edgard Garrido /Reuters)


Dr Gary Nabel from the US National Institute of Allergy and Infectious Diseases in Bethesda, and colleagues, outline their argument in this week's Nature.

"We think we ought to have learned from the lesson of 2009 [the swine flu outbreak] that when the herd immunity to these influenza viruses disappears, we're vulnerable," says Nabel.

Nabel and colleagues say H2N2 influenza killed between 1 and 4 million people between 1957 and 1968.

They warn while the virus hasn't circulated in humans for several decades, it is circulating in birds and pigs, and could easily jump into humans, as H1N1 did.

Nabel says studies suggest that the 2009 H1N1 flu pandemic came from a virus related to the deadly 1918 Spanish flu virus.

He says a closely related virus was found in pigs, and antibodies against the Spanish flu virus have been found to protect against H1N1 in mice.

According to the World Health Organization, as of May last year, the virus had led to more than 18,000 deaths worldwide.

Nabel says people were only protected from H1N1 if they were old enough to have antibodies to it, which left everyone else vulnerable.

"We found exactly the same thing for H2[N2]," says Nabel.

He and colleagues tested a sample of 90 people in the US and found that those under the age of 50 years did not have the antibodies against H2N2.

Nabel and colleagues argue that researchers should re-exaine vaccines used in the past against H2N2 and develop a vaccine that can be used before the virus jumps to humans.

"It's better to prepare when it's not urgent," says Nabel.

'Hard to sell'

Australian expert in the history of pandemics, Dr Graham Burgess says the argument is "very logical", but he thinks it will be hard to "sell".

"Selling a vaccine for something that has not happened is fairly difficult," says Burgess, of James Cook University in Townsville.

He wonders whether the money may be better spent on wider vaccination against seasonal flu, which kills between 1 and 2000, mainly elderly and young, Australians a year.

"Since about 1930 ... we've had 10 times as many deaths from seasonal viruses as we've had from pandemic viruses," says Burgess.

Dr Ian Barr of the WHO Centre for Influenza in Melbourne describes the pre-emptive vaccination plan as "a bit provocative".

"It would be a pretty bold step for something that may or may not occur," says Barr.

Barr questions the trade-off between the costs and benefits of the plan, including possible adverse effects of the vaccine.

He says vaccination against H1N1 met resistance because of these concerns.

"Even vaccines made to today's stringent standards can run into problems in terms of having unwanted side reactions," says Barr, citing the withdrawal of flu vaccinations for children last year.

"You don't really know these things until you put it into a large population," he says.

Quantifying the risk

Both Barr and Nabel agree it is very hard to quantify the risk of a pandemic coming from viruses circulating in animals.

"I couldn't tell you if you're due for one next month or in 10 years from now," says Nabel.

"It's a bit like predicting the weather."

"But, just like with the weather," he adds, "you can see some patterns emerging."

Nabel says there's no guarantee there will be a catastrophic outcome from H2N2. But, he argues given a pandemic can cost as much as US$177 billion, pre-emptive vaccination could be very cost-effective.

"Probably for a few billion dollars we could have pretty good assurance worldwide that this would never become a problem," he says.

Researchers are also working on a "universal" vaccine designed to work against all known flu strains.
