February 17, 2011

Unnecessary Flu Vaccination Policies

(Ivanhoe Newswire) "“ Rather than implementing policies to reduce the impact of a flu epidemic right away, it might be better to hold off a few weeks after the start of the outbreak, according to a new study.

When an outbreak of a severe disease such as influenza or SARS takes hold and spreads rapidly, governments consider various "social distancing" measures to limit the impact of the outbreak, for example closing schools and public places. However, the costs and societal impact of such measures means that it is undesirable to use them for a long period of time.

Researchers at Imperial College London and Utrecht University used mathematical models to consider the effectiveness of short-term interventions and evaluate the best policies for a range of objectives, such as minimizing the peak demand for public health services or minimizing the social or economic costs of containing the outbreak. They also considered different constraints, such as a limited stockpile of treatments.

According to the results, an intervention starting a few weeks into the epidemic is almost as effective at containing both the size of the epidemic and the peak number of cases below a certain target as one that starts at the beginning of the outbreak. The researchers conclude that because of the social and economic costs of imposing the policies for an extended period of time, it might be better not to implement social distancing measures straight away.

"If you can only use an intervention for a limited period of time, then it's likely that there will be a resurgence of the epidemic after the intervention is lifted. This happened in a number of American cities after the 1918 pandemic. Waiting a few weeks before starting to implement containment policies can reduce this resurgence," Dr Deirdre Hollingsworth, a Junior Research Fellow from the Medical Research Council Centre for Outbreak Analysis and Modeling at Imperial College London, was quoted as saying.

The study also found that the best policy strategy depended on the exact objectives to be achieved. In order to limit the peak prevalence of illness, weak interventions starting early are required. In order to minimize the total size of the epidemic, stronger measures are required but they can start later.

SOURCE: PLoS Computational Biology, published online February 16, 2011