Table 2.

Blood-culture-confirmed typhoid fever and vaccine efficacy

		Number at risk	Total follow-up time (person-years)	Number of cases of blood-culture-confirmed typhoid fever	Incidence rate (per 100 000 person-years; 95% CI)	Protective efficacy of Vi-TT (95% CI)	Absolute risk reduction per 1000 children (95% CI)*	Number needed to vaccinate (95% CI)†
Intention-to-treat population
Vi-TT		14 069	60 500	24	39·7 (25·4–59·0)	78·3% (66·3–86·1)	6·1 (4·5–7·7)	163 (129–222)
MenA		14 061	60 220	110	182·7 (150·1–220·2)	Ref	Ref	Ref
Age at vaccination
<2 years
	Vi-TT	1555	6586	4	60·7 (22·8–161·8)	70·6% (6·4–93·0)	6·2 (1·0–11·4)	162 (88–1035)
	MenA	1600	6773	14	206·7 (122·4–349·0)	Ref	Ref	Ref
2–4 years
	Vi-TT	3503	15 007	5	33·3 (13·9–80·1)	79·6% (45·8–93·9)	5·6 (2·6–8·6)	180 (117–391)
	MenA	3579	15 297	25	163·4 (110·4–241·9)	Ref	Ref	Ref
≥5 years
	Vi-TT	9011	38 907	15	38·6 (23·2–64·0)	79·3% (63·5–89·0)	6·3 (4·3–8·4)	158 (120–233)
	MenA	8882	38 151	71	186·1 (147·5–234·8)	Ref	Ref
Per-protocol population
Vi-TT		13 945	59 942	22	36·7 (23·0–55·6)	80·0% (68·3–87·3)	6·2 (4·6–7·8)	160 (127–216)
MenA		13 937	59 662	109	182·7 (150·0–220·4)	Ref	Ref	Ref

Vi-TT=Vi polysaccharide tetanus toxoid typhoid conjugate vaccine. MenA=meningococcal capsular group A conjugate vaccine.

^*Absolute risk reduction (risk in the MenA group minus risk in the Vi-TT group) is the total reduction in the risk of blood-culture-confirmed typhoid fever that resulted from vaccination with TCV.

^†Number needed to vaccinate is the number of children that would need to be vaccinated to prevent one case of blood-culture-confirmed typhoid fever.