In this report, we have alluded several times to the long period between the dose of IPTi administered at 3 or 4 months and the next dose given at 9 months of age and has raised questions about what occurs during that long period. In its unpublished report, the SWG estimated protective efficacies during several specific follow-up intervals to shed light on this issue. First, they assessed the level of efficacy of IPTi against all episodes of malaria in the 35-day period after a dose of SP or of placebo was given to infants 3 months of age (“prophylactic effect 1”). In infants who received SP, one would expect the levels of drug present in most infants to be protective against sensitive and moderately sensitive parasites during this 35-day period. The results are shown in the Table 8 below.

Every trial showed that a moderate or high level of protection was observed at every trial site during this 35-day period. In five of the six trials, the difference in incidence between SP and placebo groups was significant—sometimes highly significant—and the lower limit of the 95 percent CI was well above zero. Very similar results were observed in the 35 days after an IPTi dose administered at 9 months of age (“prophylactic effect 2”), as shown below in Table 9.

Of the four sites that administered IPTi doses in the second year of life, the point estimates of efficacy in the 35 days after the dose (“prophylactic effect 3”) were 92 percent (95 percent CI, 80, 95) for Tamale; 72 percent (95 percent CI, 57, 82) for Navrongo; 31 percent (95 percent CI, −3.6, 54) for Kumasi; and 29 percent (95 percent CI, −210, 84) for Lambaréné.