Scientists have predicted that by the time the new H1N1 flu vaccine is in widespread use the pandemic will have already peaked, calling into question the usefulness of vaccination programmes. Treating one third of diagnosed cases of ‘swine flu’ with antiviral drugs could push back the autumn peak of the pandemic enough to allow mass vaccination to be effective in the UK, report modellers in BMC Medicine.

 

But public health experts say the strategy is not practical in the UK or other European countries.

 

With the number of pandemic flu cases in the UK on the rise this week, health officials believe the autumn wave may have already begun. If the height of the epidemic could be postponed, it would allow health authorities time to roll out vaccination and prevent a large number of people from catching swine flu.

 

The model, published online this month, predicts that the autumn wave of the pandemic will peak between 9 October and 18 November in the UK. Current estimates suggest that the first doses of the vaccine will not be available until mid-October. The gap in vaccine coverage could be bridged by distributing antiviral drugs to 30% of confirmed cases, say Duygu Balcan, from Indiana University, USA, and colleagues.

 

“We calculate that the UK will need between 7.4 and 7.7 million doses of antiviral treatments to push back the epidemic peak for about a month,” comments Bruno Goncalves, a member of the modelling group, to EHTF News.

 

But Meirion Evans, of the National Public Health Service for Wales, believes that holding back the epidemic peak for a month would not give enough time for widespread vaccination.

 

The earliest a substantial number of vaccine doses would be available is October, with the majority not available until the end of December, Evans explains. On top of this will be the delays associated with delivering the vaccination programme to the public. It usually takes around six to eight weeks to administer seasonal flu jabs.

 

“We would have to delay the autumn peak by around two months in order to ensure the majority of the people were immunised,” says Evans. “In my view, this is simply not feasible.”

 

Other scientists have remarked that aggressive and preventative use of antiviral drugs at the start of an outbreak, but not once the epidemic takes hold, can send confusing messages to the public. Widespread use of antivirals also comes with a risk of resistance developing in the virus, the European Centre for Disease Prevention and Control (ECDC) tells ETHF News. This can happen when antiviral drugs are not taken by patients in the appropriate way.

 

Earlier this year, before the pandemic virus gained a foothold in the UK, health authorities attempted to stop the virus spreading outside schools and other institutions by handing out antiviral drugs. They administered the drugs to patients with confirmed cases of illness and people who came into contact with them.

 

There is limited evidence to suggest this tactic had any effect on the speed with which the virus spread across the country, says Evans. Taking a similar approach now is unrealistic, she argues, as the virus is already circulating widely in the community. “[Swine] flu is now endemic in the UK—rates are down but it has not gone away.”

 

The ECDC agrees that the UK’s earlier experience has revealed the pitfalls of attempting to delay widespread transmission of the virus using antiviral drugs. “It is extremely difficult to get to the right people at the right time.”

 

Closing all schools between September and December would most likely have the biggest impact on the timing of the epidemic peak, says Evans. But this would be hugely disruptive for children’s education, as well as healthcare services staffed by people with young families. “Since the illness has been relatively mild this option has been rejected,” she notes.

 

Goncalves says that delaying the height of the pandemic has other drawbacks. Postponing the peak could be a “double edged sword”, he explains: although it could buy time for vaccination, it could also push the pandemic peak to coincide with the height of the seasonal flu epidemic. This could mean that at its peak, the pandemic will affect more people than it would have done otherwise—as the virus will be circulating at higher levels when flu transmission conditions are at their optimum, he says.

 

Since the start of the swine-origin H1N1 outbreak modellers around the world, including the team at Indiana University, have been tracking the spread of the new virus to help guide health authorities’ response. Balcon and colleagues’ modelling approach takes into account how people move around the world in making predictions of how the outbreak could unfold on a global scale.

 

They predict that during the peak of the pandemic, between 723,000 and 813,000 new cases of infection will probably occur every day in the UK. In the USA, where they expect the autumn wave to peak earlier, between late September and early November, there could be up to 3,302,000 new infections per day.

 

The ECDC says the model assumes that the virus is more infectious than generally thought. The organisation also questions whether worldwide human movement data can generate reliable results, arguing that public health policies are best informed by modelling studies that use country or continent-based data on population movement and other parameters.