The issue of vaccination was not available until 1931, when a viral growth in embryonated hens' eggs was discovered, and in the 1940s, the US military developed the fi rst approved inactivated vaccines for infl uenza, which were used in the Second World War with limited success. Vaccination is the best defense against the infl uenza if the right strain is predicted, and if there are no mutations after the administration of the vaccine. In the 1957 and 1968, infl uenza vaccination programs were credited with the reduction of the severity of both pandemics. The 1976 swine fl u scare provided the general public a forum to exam the role of vaccination, when the "predicted" swine fl u pandemic failed to materialize after hundreds of thousands of Americans were vaccinated [15] . As shared by many authorities, the directions of pandemics are diffi cult to predict. Successive pandemics and pandemiclike episodes have been decreasing in severity over time. This is due to advances in medicine, public health and understanding the genetics of the disease, but this may also refl ect the evolutionary course of the virus, to that favors transmissibility with minimal pathogenicity. A virus that kills its host, or causes its host to remain at home, will not be transmitted [10] . The swine fl u scare did not result in a pandemic: was it because it lost its pathogenicity or because of the massive immunization clinics which would result in a "herd immunization"?