Figure 2. Kaplan-Meier Survival Curves of Mothers With and Without Exposure to Oral Polio Vaccine (OPV).

The shaded area represents the 95% CI of the survival in the unexposed group. For the absence of COVID-19 infections in the exposed group, calculation of the interval was not possible for that group. Person-days in the study were 1 016 182 for the unexposed group and 59 068 for the exposed group.