  We introduce an immunization method where the percentage of required
vaccinations for immunity are close to the optimal value of a targeted
immunization scheme of highest degree nodes. Our strategy retains the advantage
of being purely local, without the need of knowledge on the global network
structure or identification of the highest degree nodes. The method consists of
selecting a random node and asking for a neighbor that has more links than
himself or more than a given threshold and immunizing him. We compare this
method to other efficient strategies on three real social networks and on a
scale-free network model, and find it to be significantly more effective.
