PIP: In the course of 2 years of surveillance of whooping cough by fortnightly home visits among a population of 24,000 in a rural area of Kenya, 918 cases were observed with a peak of 218 in December 1974-January 1975. The attack rate was highest (15.8%) during the 1st year of life; for those ages 0-6 it was 12.8%. 90% of the cases occurred in children age 6 or younger. The median age was 3.5 years, the age range 1 month-13 years. Girls were significantly more affected than boys. The overall case fatality rate was 1.3% but among infants, it was 2.5 times higher. In order to contribute to the improvement of immunization coverage in countries where health resources are limited, a schedule of child immunization requiring a minimum number of contacts with the children was introduced into the study area with the aim of evaluating its effectiveness in protecting children from clinical pertussis. In this trial, the effect of 2 and 3 diphtheria-pertussis-tetanus (DPT) vaccine doses was compared. Pertussis agglutinating antibody determinations showed an equally satisfactory response after 2 and 3 DPT vaccine doses. (author's)