Cuba

Haemophilus influenzae

Naturally acquired immunity to Haemophilus influenzae type B in healthy Cuban children. 2004, Toraño Peraza, Mem Inst Oswaldo Cruz

The authors analyzed 974 healthy unvaccinated children in Cuba and found that 99.7% of them had natural immunity to Hib by the age of 4-5. Natural immunity to Hib was also found in Finland (79%) and in India ( 80%). Therefore, WHO recommends that this vaccine be introduced into the national calendar only in countries that can afford it financially without taking resources from other important vaccines.
Here reported on the natural immunity to Hia in Aborigines in Canada. More: [1].