The present invention provides a vaccine against a viral infection. The exemplary vaccine comprises a viral antigen of a vaccine strain of a virus wherein the viral antigen is derived from a virus preparation of the vaccine strain of the virus wherein the virus preparation of the vaccine strain of the virus contains a subpopulation of infectious viral particles, and the subpopulation of infectious viral particles is represented as a proportion over the total viral particles or total viral antigens of the virus preparation and wherein the proportion of the subpopulation of infectious viral particles over the total viral particles or total viral antigens of the virus preparation is over a predefined threshold so that the vaccine provides at least partial inter-subtypic or intra-subtypic cross immune response against different strains of the virus than the vaccine strain.
