A ceain commuity has 100 children out of whom 28 are immunuzed against measles; 2 of them acquire measles simultaneously; Subsequently 14 get measles. Assuming the efficacy of vaccine to be 100%. What is the sec. Attack rate -

Ans. is 'c' i.e., 20% o The impoant features of SAR : - i) The primary case is excluded from both the numerator and denominator. ii) Denominator is restricted to susceptible contacts of primary case. iii) In denominator, person should be suscetible ---> Immune person (to disease) are not susceptible to develop the disease, So they are excluded. iv) Disease should develop within the range of incubation period.