Table 2.

 Cases of leprosy in contacts of patients with newly diagnosed leprosy by treatment during four years’ follow-up, with incidence rates per 10<thin>000 person years at risk

Treatment	Leprosy				No leprosy	Total investigated	Incidence rate per 10<thin> 000 person years at risk (95% CI)
	Single lesion paucibacillary	Paucibacillary with 2-5 lesions	Multibacillary	Total
Placebo
Follow-up (years):
1-2	28	30	9	67	9939	10 006	33.59 (26.42 to 42.72)
3-4	8	11	5	24	9361	9385	12.80 (8.58 to 19.11)
1-4	36	41	14	91	—	—
Rifampicin
Follow-up (years):
1-2	15	10	4	29	9922	9951	14.59 (10.14 to 21.01)
3-4	16	8	6	30	9358	9388	16.00 (11.18 to 22.90)
1-4	31	18	10	59	—	—

Overall reduction in incidence in rifampicin group:

During years 1-2, 56.5% (95% confidence interval 32.9% to 71.9%); Rao Scott χ²=13.476 (df=1), P=0.0002; overall number needed to treat 265 (95% confidence interval 176 to 537).

During years 1-4, 34.9% (9.8% to 53.0%); Rao Scott χ²=5.4019 (df=1), P=0.02; overall number needed to treat 297 (170 to 1206).