Only Drugs And Vaccines Will Deflect Bird Flu Pandemic

In just 16 weeks, the pandemic near-saturates the US (Image: Neil Ferguson)

One of the world’s most powerful pandemic models has reached a stark conclusion: only combining a pre-pandemic vaccine with larger stocks of antiviral drugs than currently planned would really prevent mass disease. Closing borders and restricting travel will do very little.

The conclusions mirror those reached earlier this month by a separate group working with a different model in the US. But the new study has looked in detail at the effect of travel, and for the first time models the pandemic as it spreads (avi format in a zipped file, 31MB) across Britain and the US.

Neil Ferguson and colleagues at Imperial College in London, UK, used a detailed population model and a super-computer to predict the effects of different responses to a pandemic. Combined responses worked best, they found.

If most people are treated the day after symptoms appear with antiviral drugs, schools are closed as soon as a case appears, and households of cases are quarantined, the number of cases might fall by about one-fifth.

But when the household members, schoolmates and colleagues of each case are treated with preventative antiviral drugs as well, and one-fifth of the population has already received a pre-pandemic vaccine – starting with children – the number of cases fall by about 90%.

What will not work well, relative to cost, is shutting borders and stopping travel, Ferguson told New Scientist. Even a border closure that is 99.9% effective slowed the pandemic by a few weeks at the most. “That doesn’t buy you much time to make vaccine,” says Ferguson.

And that is what matters. The model shows that if you could start giving people a vaccine based on the exact the pandemic strain 30 days after it emerges, hitting 1% of the population a day – the maximum vaccine production rate – you might cut the number of cases by 97%.

“But this is beyond what we can do,” says Ferguson. It will take several months to start pandemic vaccine production, and the model shows that will be too late.

More to the point might be a vaccine based on the H5N1 bird flu now circulating, rather than an actual pandemic H5N1. Governments have made little such vaccine, because it will not exactly match the pandemic strain, so will not prevent infection completely.

But even if it cut susceptibility to the pandemic virus by only one-third, says Ferguson, it could help enormously. "If we gave that to everyone, and stockpiled 40 to 50 million antiviral treatments in Britain, we might cut the number of cases as much as 80%.”

But that is twice as much drug as the UK plans to stockpile. The planned stockpile will be enough to treat cases, but not to give every case’s contacts preventative treatment – which, the model says, could make a big difference.

Pandemic flu planning 'too slow'

By Pallab Ghosh
4-26-2006
BBC News science correspondent

The UK government has been too slow in formulating plans to combat a potentially lethal flu pandemic, a leading expert has warned.

Professor Neil Ferguson, of Imperial College London, said there were no clear plans for ensuring rapid access to vaccines and drugs.

Professor Ferguson's work, published in Nature, suggests early treatment could halve the number falling ill.

The Department of Health has dismissed the concerns.

We are perhaps behind the curve in terms of having plans to really use those stockpiles in a crisis

The Department pledged to assess the cost and benefit of Professor Ferguson's recommendations when his preliminary findings were released last December.

He recommends that the Department doubles its stockpile of anti-viral drugs, and makes vaccination of children a priority.

His calculations show drugs need to be delivered to patients - and those living with them - within 24 hours to slow the spread of disease among the general population.

That strategy, known as household prophylaxis, could reduce the number becoming ill - and potentially dying - by a half.

But at the height of a pandemic that would mean delivering more than one million courses of drug each day.

According to Professor Ferguson, the Department of Health is not geared up to do that - and has done little to develop a capability since he expressed his concerns to BBC News last year.

He said: "We are significantly ahead of the curve in terms of getting stockpiles in place - which is excellent, we need the stockpiles in order to be able to respond.

"But we are perhaps behind the curve in terms of having plans to really use those stockpiles in a crisis."

Mobile units

England's Chief Medical Officer, Sir Liam Donaldson, said the government's pandemic flu strategy was based on expert advice from the Department's Scientific Advisory Group.

He said: "A strategy of household prophylaxis will be considered alongside other possible measures.

"We will continue to work with Professor Ferguson to explore other options that could protect the public."

Professor Ferguson has called for the creation of mobile units to deliver drugs to people's homes - because it would not be possible or sensible for people to go to their GP in the usual way.

He has also called for training exercises that would simulate the outbreak of a pandemic.

However, his study shows that it would not be worth closing borders in the event of a pandemic in another country.

The Department of Health is developing exercises and a strategy on the best way to deliver drugs

But Professor Ferguson is concerned that front line doctors have not been told about the plans, and that the project has not received sufficient funds.

The Department of Health argues stockpiling a vaccine is of limited value, as there is no guarantee it would be effective against a new pandemic strain.

But Professor Ferguson said his calculations suggested that even use of an imperfect vaccine could reduce tranmission in the general population by as much as a third.

His assessment is based on a mathematical model that simulates the spread of an average flu virus.

Experts fear a pandemic could result if a particularly deadly form of bird flu, H5N1, mutates so it can easily spread from person to person.

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