Clinical efficacy of trivalent oral poliomyelitis vaccine: a case-control study.

A case-control study was carried out between May 1988 and May 1989 to assess the effectiveness of three doses of trivalent oral poliomyelitis vaccine (TOPV3) in children aged 6-35 months in Madras city. All the cases were patients with acute paralytic poliomyelitis who were residing in Madras city and were hospitalized in the Institute of Child Health; they represented 95% of such cases in the city. The diagnosis was based on clinical grounds and confirmed by stool culture which was positive in 60%. Age- and sex-matched controls, all residing in the city of Madras, were recruited concurrently from the Institute's outpatient department. There were 78 cases and 315 controls. Vaccine efficacy observed for TOPV3 was 81% (95% CI, 58-91%) for the 6-35-month age group and 86% (95% CI, 67-94%) for the 6-23-month age group. Vaccine efficacy, after controlling for age using the Mantel-Haenszel method, was 83% (95% CI, 67-91%). An unimmunized child was at 5 times greater risk of developing acute paralytic poliomyelitis than a fully immunized child.