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Baseline characteristics at enrollment into care

Between 2006 and 2012, 1338 infants under 18 months were enrolled for HIV care at
the clinic. Of these 634 were enrolled between 2009 through 2012, were aged 18 months
and above by December 2013 and included in the main analysis (Fig. 1). From November 2011, 97 of the 634 infants were actively followed-up in a study
of immune responses. Overall, we were able to link 458/634 [72 %] of the infants to
their mothers’ data.

Fig. 1. Enrollment for PMTCT care at a rural HIV clinic in Kenya. Infants enrolled between
2009 and 2012, and older than 18 months as at 31 December 2013 (?=?634), were matched to their mothers (?=?458) and used in the main analysis. Infants enrolled since 2006 were included in
the description of changes in enrollment and in HIV transmission over the years (?=?1338). PMTCT; Prevention of Mother to Child HIV-1 Transmission

The number of infants enrolling at the clinic for PMTCT systematically dropped over
the years (Fig. 2), a trend similar to enrollment for adult HIV care at the same clinic (data not shown). The number of infants enrolling for PMTCT within the first 3 months of life significantly
increased over the study period (non-parametric test for trend, p??0.001). Overall, 475 [74.9 %] infants enrolled before 3 months of age, and the
median age of enrollment of infants into care was 0.8 (IQR, 0.3 to 3.0) months (Table 1). The majority of the infants were female (?=?366 [57.7 %]), and 40 % (?=?246) lived within 5 km of the hospital.

Fig. 2. Temporal changes in infant enrollment for PMTCT care at a rural HIV clinic in Kenya.
Dashed line: infants enrolled each year. Light grey, mid-grey and dark-grey bars represent
age at enrollment: enrolled before 3 months, between 3 to 6 months and after 6 months
of age respectively. The total number of infants enrolled (?=?1338). PMTCT; Prevention of Mother to Child HIV-1 Transmission

Table 1. Characteristics of HIV-exposed infants and their HIV-1 infected mothers enrolled for
care at a rural HIV clinic in Kenya (N?=?634)

The median maternal age at delivery was 28 (IQR, 24 to 34) years. Most mothers had
primary education or less (?=?369 [80.6 %]) and were not malnourished at the time of delivery (BMI 18.5, ?=?373 [81.4 %]). Their median CD4 count at delivery was 410 (IQR, 279 to 571). The
majority of mothers were not on long-term HAART (?=?279 [60.9 %]), with only a small proportion [19.8 %] on continuous HAART for more
than 2 years prior to delivery.

Ninety-seven infants were enrolled into the immune response study. Their baseline
characteristics at enrollment did not differ from those of infants under standard
care (Table 1).

Malnutrition at enrollment into care

Of the 634 exposed infants enrolled for HIV care during the study period, 560 (88.3 %)
had baseline weight, age and height data available. A total of 285 infants (53.1 %)
exhibited at least one of the malnutrition syndromes (wasting, underweight or stunting)
and 26 (4.8 %) had a combination of all syndromes. The overall prevalence of wasting,
underweight and stunting was 14.0, 24.1 and 41.5 % respectively (Table 2) and worsened with older age at enrollment (correlation coefficients [95 % CI]: ?0.096
([95 % CI: ?0.143 to ?0.049], p??0.001); ?0.099 ([95 % CI: ?0.136 to ?0.062], p??0.001) and ?0.060 ([95 % CI: ?0.105 to ?0.016], p?=?0.008), respectively. Neither the infant’s gender, residential area nor were maternal
characteristics associated with the infant’s nutritional status at enrollment.

Table 2. Distribution of nutritional status amongst HIV-exposed infants at enrollment for PMTCT
care at a rural HIV clinic in Kenya (N?=?634)

Retention in care over the recommended PMTCT 18-month period

Overall, 634 infants were followed up and contributed a total of 6577 person months
of observation (pmo). Of these, 247 (39.0 % [95 % CI, 35.1 to 42.9]) were lost to
follow-up before 18 months of age: incident rate 3.76 (95 % CI, 3.3 to 4.2)/100 pmo.
Sixty-one (9.6 %) of the nfants were enrolled but did not return for any follow-up
care, and by 9 months of age, 158 (26.4 %) had dropped out.

The infant’s age, calendar year at enrollment, nutritional status and active follow-up,
were independently associated with non-retention in care. Infants enrolled at 6 months
of age were almost twice as likely to drop out (Table 3). Infants enrolled in later calendar years had better retention in care (p?=?0.003). Infants with malnutrition syndromes at enrollment were more likely to drop
out compared to those without malnutrition. Infants not on active follow-up were more
likely to drop out of care, compared to those receiving active follow-up (HR [95 %
CI] 6.6 [2.9 to 14.6], p??0.001).

Table 3. Predictors of retention in care amongst HIV-exposed infants enrolled for PMTCT (N?=?634)

Infants born to mothers with malnutrition at the time of the infant’s birth had a
higher rate of drop out from care compared to those born to mothers without malnutrition
(HR [95 % CI] 1.6 [1.1 to 2.5], p?=?0.036). Mothers not on HAART for more than 2 years prior to the infant’s delivery
were almost three-fold more likely to drop out of PMTCT care compared to mothers on
long-term HAART (Table 3).

Correlates of MTCT of HIV-1 infection amongst infants enrolled for PMTCT care

The proportion of enrolled infants who became HIV-infected declined from 19.4 % in
2006 to 8.9 % in 2012 [non-parametric test for trend, p?=?0.024] (Fig. 3). Of the 634 infants within the study period (2009 to 2013), HIV test results were
available for 444 (70.0 %) infants. Overall, 57 infants became infected before age
18 months, suggesting an overall MTCT risk during follow up of 12.8 % (95 % CI, 10.4–16.9)
[Table 4]. More than half of the infants who enrolled into care after 6 months of age became
HIV infected before age 18 months.

Fig. 3. Prevalence of HIV vertical transmission among infants enrolled for PMTCT care at a
rural HIV clinic in Kenya Dotted lines: prevalence during previous study, solid lines:
prevalence during current study. Non-parametric test for trend, p?=?0.024, confidence interval (CI) indicated. Total number of infants (?=?1338). PMTCT; Prevention of Mother to Child HIV-1 Transmission, MTCT; Mother to
child Transmission of HIV

Table 4. Correlates of mother to child transmission of HIV-1 infection amongst HIV-1 exposed
infants enrolled for care (N?=?634)

Age at enrollment, nutritional status, residential distance from the hospital and
mothers’ HAART status at the time of delivery were independently associated with MTCT
of HIV infection (Table 4). Infants enrolled into care after 6 months of age had much higher odds of HIV-infection
compared to those enrolled for care within 3 months of age (aOR [95 % CI]: 23.3 [8.3
to 65.4], p??0.001) while infants who exhibited any of the malnutrition syndromes were twice
as likely to have acquired HIV-1 (aOR [95 % CI]: 2.3 [1.0 to 5.2], p?=?0.038). Infants residing more than 10 km from the hospital were twice as likely
to acquire HIV infection compared to those living within 5 km of the hospital. Infants
born to mothers who were not on HAART at the time of the infant’s birth had more than
six-fold odds of HIV infection compared to those born to mothers who had been on HAART
for more than 24 months prior to delivery (aOR [95 % CI] 6.5 [1.4 to 29.4], p?=?0.004).