  Finding optimal policies to reduce the morbidity and mortality of the ongoing
pandemic is a top public health priority. Using a compartmental model with age
structure and vaccination status, we examined the effect of age specific
scheduling of vaccination during a pandemic influenza outbreak, when there is a
race between the vaccination campaign and the dynamics of the pandemic. Our
results agree with some recent studies on that age specificity is paramount to
vaccination planning. However, little is known about the effectiveness of such
control measures when they are applied during the outbreak. Comparing five
possible strategies, we found that age specific scheduling can have a huge
impact on the outcome of the epidemic. For the best scheme, the attack rates
were up to 10% lower than for other strategies. We demonstrate the importance
of early start of the vaccination campaign, since ten days delay may increase
the attack rate by up to 6%. Taking into account the delay between developing
immunity and vaccination is a key factor in evaluating the impact of
vaccination campaigns. We provide a general framework which will be useful for
the next pandemic waves as well.
