HIV Incidence

Using unweighted data, 12,357 of pre-cohort participants tested as HIV-uninfected and were thus eligible for enrollment in the incidence cohort, Cohort 1 (Note: eligible participants were individuals who tested uninfected by rapid testing and by NAAT). Of eligible participants, 11,880 (96%) were enrolled and 477 (4%) refused. Among this enrolled cohort, 11,155 (94%) completed follow-up and 10,924 (88%) received HIV testing at the follow-up visit.

Table 1: Demographic Characteristics of HIV-uninfected Adults in Swaziland, by Gender*

Total Men Women
Overall Number 11840 6025 5815
Age, mean (years) 28.3 27.4 29.3
Rural dweller 70% 71% 70%
Education of completing high school or higher 68% 69% 68%
Unemployed 45% 34% 57%
Not married nor living with partner 59% 70% 48%
Sexually active** 70% 63% 78%
>2 sex partners** 10% 17% 3%
Consistent condom use** 19% 20% 17%

*Weighted analysis
**In the 6 months prior to pre-cohort survey interview

Weighted analysis, which allows Cohort 1 data to be generalized to the national population, indicates that the mean age of HIV-uninfected adults in Swaziland in 2011 was 28 years and that 70% percent lived in rural areas [Table 1]. Sixty eight percent had a secondary education or higher, and almost half were unemployed (34% of men and 57% of women). Seventy percent of men and 48% of women were not married nor living with a partner. Sixty three percent of men and 78% of women reported being sexually active in the previous six months with 17% of men and three percent of women reporting two or more sexual partners in this time period. Among persons reporting being sexually active in the prior six months, approximately 20% of both men and women reported consistent condom use.

The overall incidence measurement was 2.4/100 PY. Incidence among men was 1.7/100 PY, and was almost twice as high among women at 3.1/100 PY [Table 2]. The patterns of HIV incidence for men and women were quite different with a peak of 3.1/100 PY in men aged 30-34, and two peaks seen in women at ages 20-24 and 35-39 of 4.2/100 PY and 4.1/100 PY respectively [Figure 1]. Among women, incidence was higher in those not married nor living with a partner (4.1/100 PY), those with 2 or more partners (9.6/100 PY) (which was only three percent of the study population), and reporting pregnancy (4.4/100 PY). Among men, incidence was higher in those not married nor living with a partner (1.8/100 PY), reporting inconsistent condom use (2.7/100 PY), those with 2 or more partners (3.2/100 PY), and those who were uncircumcised (1.7/100 PY) [Table 3].

Table 2: HIV Incidence in Swaziland

Sero-
conversions Person
 years (PY) of Follow-up Incidence/
100 PY 95% CI Incidence/
100 PY
Overall 143* 6019 2.38 2.06-2.75
Men 51 3070 1.65 1.28-2.11
Women 93 2949 3.14 2.63-3.74

*Columns will not sum due to sample weighting

HIV Incidence in Swaziland by Age and Sex (95% confidence intervals represented with vertical bars)

HIV Incidence in Swaziland by Age and Sex - Men HIV Incidence in Swaziland by Age and Sex - Women

The multivariable model, adjusted for education, employment, geography, number of sex partners, and pregnancy, showed that independent predictors of seroconversion among women were age (20-24, HR 2.03, 95% CI 1.01-4.05; 35-39 HR 2.85, 95% CI 1.02-7.98), not being married nor living with a partner (HR 3.05, 95% CI 1.64-5.69), having a partner that lived elsewhere (HR 2.81, 95%CI 1.53-5.15), and having an HIV positive partner (HR 1.88, 95% CI 1.09-3.27) or a partner of unknown HIV status (HR 2.74, 95% CI 1.53-4.92). Among men, significant predictors of seroconversion included not knowing a partner’s HIV status (HR 3.72, 95% CI 1.97-7.05) and inconsistent condom use (HR 2.35, 95% CI 1.16-4.73).

Table 3: HIV Incidence by Demographics and Behaviors

Men Women
Incidence/
100 PY 95% CI Incidence/
100 PY 95% CI

Marital Status

Married/living together 1.34 (0.79-2.27) 2.24 (1.52-3.02)
Not married/not living together 1.80 (1.36-2.38) 4.06 (3.28-5.03)

Condom Use, past 6 months*

Consistent use 1.74 (1.05-2.89) 3.78 (2.65-5.37)
Inconsistent use 2.70 (2.01-3.61) 3.78 (3.03-4.66)

# Sex Partners, past 6 months

Never had sex 0.15 (0.03-0.83) 0.71 (0.22-2.26)
0 0.40 (0.08-2.05) 1.21 (0.61-2.38)
1 1.92 (1.40-2.64) 3.64 (3.01-4.41)
> 2 3.21 (2.02-5.10) 9.64 (4.48-20.0)

MC Status, self report

Circumcised 1.29 (0.71-2.33) NA*
Uncircumcised 1.74 (1.32-2.30) NA*

Pregnant, self report

NA* - 4.38 (1.86-10.1)

*Among participants reporting sexual activity