Immunity to fowlpox.

Protection against fowlpox develops following vaccination or natural infection. The immune response can be measured for variable times either by challenging immunity of vaccinated birds for protection or by various serologic tests, e.g., viral neutralization, agar gel precipitation, complement fixation, passive hemagglutination, fluorescent antibody, and immunoperoxidase methods. Variation in the antibody response measured by these tests may be due to concentration of antibody present and sensitivity of the test employed. Available information suggests that both humoral and cellular immunity are involved in protection. There is a possibility of persistence of virus in latent infections which also might be responsible for protection.