Table 2.
ITT analysis of malaria infection prevalence by main effect and for each individual intervention at 4, 9, 16, and 21 months after intervention
| n/N (%) | OR (95% CI) | p value | ||
|---|---|---|---|---|
| Survey A, 2015, 4 months after intervention | ||||
| Main effect comparison (factorial analysis) | ||||
| No PBO LLIN* | 936/1991 (47%) | 1 (ref) | .. | |
| PBO LLIN† | 798/1926 (41%) | 0·68‡ (0·39–1·18) | 0·1630 | |
| No IRS§ | 998/1968 (51%) | 1 (ref) | .. | |
| IRS¶ | 736/1949 (38%) | 0·50‡ (0·31–0·82) | 0·0071 | |
| Interaction coefficient | .. | 1·37 (0·66–2·86) | 0·3825 | |
| Individual group comparison | ||||
| Standard LLIN | 553/997 (55%) | 1 (ref) | .. | |
| PBO LLIN | 445/971 (46%) | 0·68‖ (0·39–1·18) | 0·1630 | |
| Standard LLIN plus IRS | 383/994 (39%) | 0·50‖ (0·31–0·82) | 0·0071 | |
| PBO LLIN plus IRS | 353/955 (37%) | 0·47‖ (0·28–0·79) | 0·0048 | |
| Survey B, 2015, 9 months after intervention | ||||
| Main effect comparison (factorial analysis) | ||||
| No PBO LLIN* | 767/1809 (42%) | 1 (ref) | .. | |
| PBO LLIN† | 531/1852 (29%) | 0·37 (0·21–0·65) | 0·0011 | |
| No IRS§ | 790/1815 (44%) | 1 (ref) | .. | |
| IRS¶ | 508/1846 (28%) | 0·33 (0·19–0·55) | <0·0001 | |
| Interaction coefficient | .. | 2·43 (1·19–4·97) | 0·0158 | |
| Individual group comparison | ||||
| Standard LLIN | 515/932 (55%) | 1 (ref) | .. | |
| PBO LLIN | 275/883 (31%) | 0·37 (0·21–0·65) | 0·0011 | |
| Standard LLIN plus IRS | 252/877 (29%) | 0·33 (0·19–0·55) | <0·0001 | |
| PBO LLIN plus IRS | 256/969 (26%) | 0·29 (0·17–0·49) | 0·0001 | |
| Survey C, 2016, 16 months after intervention | ||||
| Main effect comparison (factorial analysis) | ||||
| No PBO LLIN* | 941/2017 (47%) | 1 (ref) | .. | |
| PBO LLIN† | 611/1910 (32%) | 0·47 (0·26–0·87) | 0·0173 | |
| No IRS§ | 890/2018 (44%) | 1 (ref) | .. | |
| IRS¶ | 662/1909 (35%) | 0·59‡ (0·34–1·04) | 0·0652 | |
| Interaction coefficient | .. | 1·30 (0·59-2·86) | 0·5045 | |
| Individual group comparison | ||||
| Standard LLIN | 548/1034 (53%) | 1 (ref) | .. | |
| PBO LLIN | 342/984 (35%) | 0·47‖ (0·26–0·87) | 0·0173 | |
| Standard LLIN plus IRS | 393/983 (40%) | 0·59‖ (0·34–1·04) | 0·0652 | |
| PBO LLIN plus IRS | 269/926 (29%) | 0·36 (0·20–0·66) | 0·0014 | |
| Survey D, 2016, 21 months after intervention | ||||
| Main effect comparison (factorial analysis) | ||||
| No PBO LLIN* | 1255/2034 (62%) | 1 (ref) | .. | |
| PBO LLIN† | 865/1930 (45%) | 0·40‡ (0·20–0·81) | 0·0122 | |
| No IRS§ | 1150/2002 (57%) | 1 (ref) | .. | |
| IRS¶ | 970/1962 (49%) | 0·58‡ (0·29–1·14) | 0·1130 | |
| Interaction coefficient | .. | 1·59 (0·62–4·07) | 0·3282 | |
| Individual group comparison | ||||
| Standard LLIN | 710/1044 (68%) | 1 (ref) | .. | |
| PBO LLIN | 440/958 (46%) | 0·40‖ (0·20–0·81) | 0·0122 | |
| Standard LLIN plus IRS | 545/990 (55%) | 0·58‖ (0·29–1·14) | 0·1130 | |
| PBO LLIN plus IRS | 425/972 (44%) | 0·37‖ (0·19–0·73) | 0·0056 | |
ORs for the factorial analysis compared the two main intervention effects (no PBO LLIN vs PBO LLIN, and no IRS vs IRS) and their interaction, and compared each of the intervention to the standard LLIN in the individual group analysis. OR was unadjusted for baseline plasmodium infection prevalence. Plasmodium infection prevalence is reported for children aged 6 months to 14 years. OR=odds ratio. LLIN=long-lasting insecticidal net. PBO=piperonyl butoxide. IRS=indoor residual spraying. ITT=intention to treat.
Standard LLIN and standard LLIN plus IRS.
PBO LLIN and PBO LLIN plus IRS.
Reduction in prevalence is less than the 28% difference defined a priori for the main effect.
Standard LLIN and PBO LLIN.
Standard LLIN plus IRS and PBO LLIN plus IRS.
Reduction in prevalence is less than the 40% defined a priori for the individual arm comparison.