What is "premunity"

Premunity is a term used to signify progressive development of immunity in individuals exposed to an infective agent, mainly belonging to protozoa and Rickettsia, but not in viruses. After the initial infection, which generally occurs in childhood, the effect in subsequent infections is diminished. Infections thereafter may exhibit little or no symptomatology in spite of parasitemia. The next stage is resistance to infection altogether.

Loss of premunity is estimated to be the cause of the rebound of malaria in 1965 in India after the dramatic success of the National Malaria Control Programme that was launched for rural India in 1953. It led to the adoption of the Modified Plan of Operation (MPO).