Key points are not available for this paper at this time.
Nan Lin, Ralph Hingson, Juan Allwood-Paredes, Mass Immunization Campaign in El Salvador, 1969: Evaluation of Receptivity and Recommendation for Future Campaigns, HSMHA Health Reports, Vol. 86, No. 12 (Dec., 1971), pp. 1112-1121
Lin et al. (Fri,) studied this question.