Fig. 1

tOPV response to the three serotypes, by number of doses, in a clinical trial in Brazil, 1989[30]. a Marginal seroconversion rates, defined as the incremental number of children seroconverting after each dose, divided by the number of children that did not yet seroconvert prior to the dose. b Relative cumulative tOPV seroconversion rates, defined as cumulative seroconversion rate for the given serotype after the given number of doses, divided by cumulative seroconversion rate for serotype 2 after the same number of doses