We read a great deal about work in progress to develop a vaccine to combat the bird flu, and are accustomed to rolling up our sleeves for flu shots. However this approach works better for bacteria and for larger organisms than it can for any virus. Every virus has an innate ability to adapt and change form. The pathogenic types that infect humans may well have their origins in lower life forms. The main kinds of human flu virus are probably related to their close cousins from the avian world. Natural immunity and some modern therapeutic forms of intervention can boost immunity, or can act by attacking the causative virus. However neither of these approaches provides certain protection against virus attack, for the pathogens are able to adjust and survive through every adversity.
There is a fairly standard method to prepare a vaccine to guard against a virus attack, but the limitation is that the vaccine will not work against a modified form that the virus can quickly assume. Stable immunity builds up over generations. People who live in isolation gradually evolve powers of resistance to combat known virus forms prevalent in their environment. This system of protection becomes vulnerable as soon as people move to a new environment or once a new pathogen is introduced in their midst. A flu shot certainly helps against one type of virus, but can be entirely useless when the virus mutates or if a new virus is introduced in to the environment. Do not count on a bird flu vaccine alone to keep the bug away!