Table 2:

Immunity to poliovirus type 2 immunity 28 months following single-dose IPV or 30 days after a single dose of IPV

	Previous IPV group (n=234)	No previous IPV group (n=224)	p value
Enrolment (day 0 visit)
Seroprevalence	100 (43%)	0	NA
Titre	<8 (<8 to <8)	<8 (<8 to <8)	1·00
Day 7 visit
Priming immune response	133/134 (99%)	NV	NA
Titre	≥1448 (≥1448 to ≥1448)	NV	NA
Day 30 visit
Seroconversion	0/1	223	NA
Titre	NA	576 (455 to 724)	NA
Day 37 visit
Priming immune response	NV	1/1 (100%)	NA
Titre	NV	NA	NA
Immunity after one IPV dose*	233 (>99%)†	224 (100%)‡	1·00
Antibody titres after two IPV doses	≥1448 (≥1448 to ≥1448)	724 (576 to 910)	0·0006

Data are n (%), n/N (%), or median (95% CI). IPV=inactivated poliovirus vaccine. NA=not applicable. NV=no visit.

^*In the previous IPV group, the challenge IPV dose was administered 28 months after first IPV dose (administered at median age of 4 months); in the no previous IPV group, the challenge IPV dose was administered 1 month after first IPV dose (administered at median age 9 months [IQR 9–10]); in both arms blood was collected 7 days after the challenge IPV dose to assess priming immune responses.

^†Immune response was seroprevalence (reciprocal antibody titre 8 or more) and priming immune response.

^‡Immunity was seroconversion and priming immune response.