The World Health Organization has continued to monitor the spread of H1N1, in part so that it can issue guidance on the production of pandemic flu vaccines in the near future.
Work under way on candidate viruses will continue until the end of June or July, after which drug companies can start developing and testing H1N1 vaccines, says acting WHO assistant director-general Keiji Fukuda.
According to a recent report by Reuters, the WHO expects to make recommendations about the best balance between H1N1 and seasonal flu vaccine-making "sometime during the summer," Fukuda said.
Pharmaceutical companies reportedly have also stepped up production of vaccines effective against this particular strain of the virus. However, if the spread of the disease increases significantly in the autumn, as some scientists predict, it is unlikely that supplies of the new vaccine will be sufficient to vaccinate entire populations.
Targeting children may be an effective use of limited supplies of flu vaccine, according to research funded by the Wellcome Trust and the EU. In the research published in the journal Epidemiology and Infection, Dr. Thomas House and Professor Matt Keeling from the University of Warwick have used computer modelling to predict the spread of pandemic influenza and to look at ways of controlling it effectively, particularly where supplies of vaccine are not sufficient for universal coverage.
The two researchers showed that, as might be expected, the disease is likely to spread fastest in densely-populated conurbations, suggesting that these should be priority areas for tackling the spread. However, they showed that vaccinating entire households at random was an inefficient use of resources; instead, vaccinating key individuals offered sufficient protection to others in their household.
Although a simplification of the complex reality of pandemic flu transmission, the researchers believe their model provides a robust argument for vaccinating children according to a news release.
"Our models suggest that the larger the household - which in most cases means the more children living at home - the more likely the infection is to spread," says Professor Keeling. "This doesn't mean that everyone in the household needs to be vaccinated, but suggests that vaccination programmes for children might help control a potential pandemic."
The researchers argue that targeting children for vaccination would not only help protect those at greatest risk of exposure to the virus, but would also offer protection to unvaccinated adults. This so-called "herd immunity" effect would mean that significantly less vaccine would be necessary to help control the spread of the virus than if it were offered to everyone.
"Given that children are generally at particular risk from the disease, we believe that vaccination programs for the young can be justified," says Dr House. "Although not sufficient to prevent a pandemic in themselves, such steps may support other control measures such as social distancing, antiviral drugs or quarantine."
In every city the researchers studied, households are seen to play a key role in the transmission of close-contact diseases like influenza, Dr. House noted.
