Measles and measles vaccine isolated amerindian tribes. I. The 1971 Trio ((Tiriyo) epidemic.

Measles in an unvaccinated virgin population exacted a death toll of 4.2% which fell particularly hard on the age groups which would ordinarily be protected by maternal antibody. The organ system most affected was quite variable. When the virus spread to a largely vaccinated village it caused only one death. Herd immunity seemed to protect many who were not vaccinated. Vaccine failed to protect 7.7% of the recipients. Some of these failures may have been due to erroneous record, vaccination in the presence of maternal antibody or inactivated vaccine, but most occurred in a few family groups related by genetics and similar past immunological experience.