Nigeria - Nigeria HIV-AIDS Indicator and Impact Survey (NAIIS) 2018

This cross-sectional, household-based survey will use a two-stage cluster sampling design (enumeration area followed by households). The target population is people 15-64 and children ages 0-14 years. The overall size and distribution of the sample is determined by analysis of existing estimates of national HIV incidence, sub-national HIV prevalence, and the number of HIV-positive cases needed to obtain estimates of VLS among adults 15-64 years for each of the 36 states and the FCT while not unnecessarily inflating the sample size needed.
From a sampling perspective, the three primary objectives of this proposal are based on competing demands, one focused on national incidence and the other on state-level estimates in a large number of states (37). Since the denominator used for estimating VLS is HIV-positive individuals, the required minimum number of blood draws in a stratum is inversely proportional to the expected HIV prevalence rate in that stratum. This objective requires a disproportionate amount of sample to be allocated to states with the lowest prevalence. A review of state-level prevalence estimates for sources in the last 3 to 5 years shows that state-level estimates are often divergent from one source to the next, making it difficult to ascertain the sample size needed to obtain the roughly 100 PLHIV needed to achieve a 95% confidence interval (CI) of +/- 10 for VLS estimates.
An equal-size approach is proposed with a sample size of 3,700 blood specimens in each state. Three-thousand seven hundred specimens will be sufficiently large to obtain robust estimates of HIV prevalence and VLS among HIV-infected individuals in most states. In states with a HIV prevalence above 2.5%, we can anticipate 95% CI of less than +/-10% and relative standard errors (RSEs) of less than 11% for estimates of VLS. In these states, with HIV prevalence above 2.5%, the anticipated 95% CI around prevalence is +/- 0.7% to a high of 1.1-1.3% in states with prevalence above 6%. In states with prevalence between 1.2 and 2.5% HIV prevalence estimates would remain robust with 95% CI of +/- 0.5-0.6% and RSE of less than 20% while 95% CI around VLS would range between 10-15% (and RSE below 15%). With this proposal only a few states, with HIV prevalence below 1.0%, would have less than robust estimates for VLS and HIV prevalence.
The evaluation of this “equal-size” approach to the 37 strata are presented in Table 1 below using the 2016 Spectrum estimates with states sorted by prevalence level from highest to lowest. This “equal-size” approach will ensure sufficiently large sample in each state for comparisons between states and satisfy overall need for national incidence estimate. As a result of the “equal-size” approach and the large number of strata (37) it is anticipated that the RSE for a national incidence estimate will be quite small, at less than 9%, when the survey is complete. It is also anticipated that regional incidence estimates (6 regions) will be possible with RSEs of 30% or less.


A total of 101,267 households were selected, 89,345 were occupied and 83,909 completed the household interview .
• For adults aged 15-64 years, interview response rate was 91.6% for women and 88.2% for men; blood draw response rate was 92.9% for women and 93.6% for men.
• For adolescents aged 10-14 years, interview response rate was 86.8% for women and 86.2% for men; blood draw response rate was 91.2% for women and 92.3% for men.
• For children aged 0-9 years, blood draw response rate was 68.5% for women and men.


The following weights have been computed and are included in the data files. Use of these weights will assure that the results produced are representative. Weights are computed at the state level.

1. Household weight


2. Individual Participant weight


3. Adolescent weight


4. Network Scale-up Method (NSUM)


5. Children's biometric


6. Adult biometric