Susceptibility of healthcare workers in Kenya to hepatitis B: new strategies for facilitating vaccination uptake.

Hepatitis B virus (HBV) infection is preventable, yet many healthcare workers (HCWs) in resource-poor countries remain at risk. The aims of this study were to evaluate the susceptibility of HCWs in a Kenyan district to HBV infection, and the feasibility of expanding the Extended Programme of Immunization (EPI) for infants to incorporate hepatitis B vaccination of HCWs. HCWs in Thika district, Kenya were invited to complete an interviewer-administered questionnaire about their immunization status and exposure to blood or body fluids. Participants were asked to provide a blood sample to assess natural or vaccine-induced protection against HBV. All non-immune HCWs were offered hepatitis B vaccination. Thirty percent (168/554) of HCWs reported one or more needlestick injuries (NSIs) in the previous year, with an annual incidence of 0.97 NSIs/HCW/year. Only 12.8% (71/554) of HCWs had received vaccination previously and none had been screened for immunity or for hepatitis B surface antigen. In total, 407 staff provided blood samples; 41% were HBV core antibody, 4% expressed hepatitis B surface antibody from previous vaccination, and 55% were unprotected. Two hundred and twenty-two staff were eligible for vaccine delivered through the EPI infrastructure. Self-motivated uptake of a full course of vaccine was 92% in the smaller health centres and 44% in the district hospital. This study demonstrates the importance of hepatitis B vaccination of HCWs in parts of Africa where high exposure rates are combined with low levels of vaccine coverage. High rates of vaccination can be achieved using childhood immunization systems for the distribution of vaccine to HCWs.

Sexual behavior, sexually transmitted diseases, male circumcision and risk of HIV infection among women in Nairobi, Kenya.

OBJECTIVE: To study risk factors for HIV infection among women in Nairobi, Kenya, as the epidemic moves beyond high-risk groups. DESIGN: A cross-sectional case-control study among women attending two peri-urban family planning clinics. METHODS: A total of 4404 women were enrolled after giving written informed consent. Information on risk factors was obtained by interview using a structured questionnaire. Blood was taken for HIV and syphilis testing, and genital specimens for gonorrhea and trichomoniasis screening. RESULTS: Two hundred and sixteen women (4.9%; 95% confidence interval, 4.3-5.5) were HIV-1-positive. Although risk of HIV was significantly increased among unmarried women and among women with multiple sex partners, most seropositive women were married and reported only a single sex partner in the last year. Women with a history or current evidence of sexually transmitted disease were at significantly increased risk; however, the prevalence of these exposures was low. Women whose husband or usual sex partner was uncircumcised had a threefold increase in risk of HIV, and this risk was present in almost all strata of potential confounding factors. Only 5.2% of women reported ever having used a condom. CONCLUSIONS: These data suggest that, among women who are not in high-risk groups, risk of HIV infection is largely determined by their male partner's behavior and circumcision status. Interventions designed to change male sexual behavior are urgently needed.

Viral etiology and epidemiology of acute respiratory infections in children in Nairobi, Kenya.

Acute respiratory infection (ARI) is the most common cause of illness and death in young children worldwide. Because of inadequate laboratory facilities and financial resources the etiological agents responsible for most cases in developing countries remain unknown, thus obviating appropriate management. Therefore, an ARI program was commenced at the Kenyatta National Hospital, Nairobi, Kenya in 1981 with the objectives of establishing the microbial causes, clinical presentations, and diagnoses of ARI in children under 5 years of age and of developing simple, rapid, and inexpensive diagnostic techniques. Viruses were demonstrated in 54% of the 822 children studied, but over half of the viruses identified were types not commonly associated elsewhere with the causation of severe ARI. Respiratory syncytial, parainfluenza, and adenoviruses occurred in the same age groups and during similar weather conditions as elsewhere. Measles virus occurred most frequently in those 7 to 9 months old. Herpes simplex, rhino-, and enteroviruses play causative roles in some cases of severe ARI in Kenyan children. A combination of immunofluorescent and cell culture techniques were shown to be essential for the detection of viruses.

First recorded outbreak of yellow fever in Kenya, 1992-1993. I. Epidemiologic investigations.

Outbreaks of yellow fever (YF) have never been recorded in Kenya. However, in September 1992, cases of hemorrhagic fever (HF) were reported in the Kerio Valley to the Kenya Ministry of Health. Early in 1993, the disease was confirmed as YF and a mass vaccination campaign was initiated. Cases of suspected YF were identified through medical record review and hospital-based disease surveillance by using a clinical case definition. Case-patients were confirmed serologically and virologically. We documented 55 persons with HF from three districts of the Rift Valley Province in the period of September 10, 1992 through March 11, 1993 (attack rate = 27.4/100,000 population). Twenty-six (47%) of the 55 persons had serologic evidence of recent YF infection, and three of these persons were also confirmed by YF virus isolation. No serum was available from the other 29 HF cases. In addition, YF virus was isolated from a person from the epidemic area who had a nonspecific febrile illness but did not meet the case definition. Five patients with confirmed cases of YF died, a case-fatality rate of 19%. Women with confirmed cases of YF were 10.9 times more likely to die than men (P = 0.010, by Fisher's exact test). Of the 26 patients with serologic or virologic evidence of YF, and for whom definite age was known, 21 (81%) were between 10 and 39 years of age, and 19 (73%) were males. All patients with confirmed YF infection lived in rural areas. There was only one instance of multiple cases within a single family, and this was associated with bush-clearing activity. This was the first documented outbreak of YF in Kenya, a classic example of a sylvatic transmission cycle. Surveillance in rural and urban areas outside the vaccination area should be intensified.

First recorded outbreak of yellow fever in Kenya, 1992-1993. II. Entomologic investigations.

The first recorded outbreak of yellow fever in Kenya occurred from mid-1992 through March 1993 in the south Kerio Valley, Rift Valley Province. We conducted entomologic studies in February-March 1993 to identify the likely vectors and determine the potential for transmission in the surrounding rural and urban areas. Mosquitoes were collected by landing capture and processed for virus isolation. Container surveys were conducted around human habitation. Transmission was mainly in woodland of varying density, at altitudes of 1,300-1,800 m. The abundance of Aedes africanus in this biotope, and two isolations of virus from pools of this species, suggest that it was the principal vector in the main period of the outbreak. A third isolate was made from a pool of Ae. keniensis, a little-known species that was collected in the same biotope. Other known yellow fever vectors that were collected in the arid parts of the valley may have been involved at an earlier stage of the epidemic. Vervet monkeys and baboons were present in the outbreak area. Peridomestic mosquito species were absent but abundant at urban sites outside the outbreak area. The entomologic and epidemiologic evidence indicate that this was a sylvatic outbreak in which human cases were directly linked to the epizootic and were independent of other human cases. The region of the Kerio Valley is probably subject to recurrent wandering epizootics of yellow fever, although previous episodes of scattered human infection have gone unrecorded. The risk that the disease could emerge as an urban problem in Kenya should not be ignored.

Marburg, Ebola and Rift Valley Fever virus antibodies in East African primates.

Sera from 464 primates held at four institutes in Kenya were tested by indirect immunofluorescence for the presence of antibodies against Marburg, Ebola, Congo haemorrhagic fever, Rift Valley fever and Lassa viruses. Four of 136 vervet monkeys were positive for Marburg virus antibodies and three of 184 baboons had antibodies against Ebola virus. One baboon was positive for Marburg virus antibodies. Two vervet monkeys, three baboons and one grivet monkey (of 56 tested) had antibodies against Rift Valley fever virus. No Congo or Lassa virus antibodies were detected. A sample of 88 sera of more arboreal primates (Sykes, blue and colobus monkeys) were negative against all five antigens, as were sera from 58 staff members of the institutes who worked with or near the animals.

Antibodies against haemorrhagic fever viruses in Kenya populations.

Human sera from Lodwar (77 sera), Nzoia (841 sera), Masinga (251 sera), Laisamis (174 sera) and the Malindi/Kilifi area (556 sera) in Kenya were tested by indirect immunofluorescence for antibodies against Marburg, Ebola (Zaire and Sudan strains), Congo haemorrhagic fever, Rift Valley fever and Lassa viruses. Antibodies against Ebola virus, particularly the Zaire strain, were detected in all regions and were, over-all, more abundant than antibodies against the other antigens. Ebola and Marburg antibody prevalence rates were highest in the samples from Lodwar and Laisamis, both semi-desert areas. Antibodies against Rift Valley fever virus were also highest in the Lodwar sample followed by Malindi/Kilifi and Laisamis. Congo haemorrhagic fever virus antibodies were rare and no antibodies against Lassa virus were detected in the 1899 sera tested.

An outbreak of poliomyelitis caused by poliovirus type I in captive black and white colobus monkeys (Colobus abyssinicus kikuyuensis) in Kenya.

In the latter part of 1982, three black and white colobus monkeys, Colobus abyssinicus kikuyuensis, from a small breeding group maintained at the Institute of Primate Research in Kenya, became paralysed within one month. Two of these cases were fatal and the third animal survived. The clinical and pathological findings suggested a poliomyelitis-like disease. This was confirmed by the isolation of wild strains of poliomyelitis virus type I from faeces, spleen, kidney, lung and central nervous system from affected animals.

Contraceptive use and the risk of HIV infection in Nairobi, Kenya.

OBJECTIVES: To determine: (a) the prevalence of human immunodeficiency virus-1 (HIV-1) infection among women attending family planning clinics in Nairobi; and (b) the associations between contraceptive use and HIV infection. METHODS: History, clinical examination and laboratory tests were used to obtain data from 4404 women attending family planning clinics in Nairobi. We conducted a case-control study comparing HIV seropositive and seronegative women with regard to previous and current use of contraception. RESULTS: The overall prevalence of HIV-1 infection was 4.9% (95% C.I. 4.3-5.5). Previous and current use of oral contraceptives (OC), injectable contraceptives and the intrauterine device were not associated with a significant increase in risk, while current users of condoms had a non-significant reduction in risk. OC use was significantly associated with cervical ectopy, but no significant association was evident between ectopy and HIV infection. CONCLUSION: The finding of no significant association between past or current OC use and risk of HIV infection suggests that any independent association that may exist between OC use and HIV risk is not large.

Threat of Marburg and Ebola viral haemorrhagic fevers in Africa.

Marburg and Ebola viruses are members of the filovirus family that can be regarded as recently emerged. These viruses have caused sporadic outbreaks of fatal haemorrhagic disease in Africa, Europe and recently in the USA. The case fatality rates rank among the highest ranging from 33-80%. The mode of transmission of these viruses are clearly through close contact with blood and body fluids. Disease outbreaks have been amplified in hospital situations with poor blood precautions. In villages disease has been amplified through contamination with blood and fluids during nursing the sick and burial rituals. The source of the viruses has eluded discovery and new theories regarding the nature of these viruses are being entertained. The threat of new outbreaks in Africa is real since serological evidence of the presence of the virus has been documented in Kenya, Sudan, Zaire, Zimbabwe, Gabon, Cote-d'Ivoire and Gabon.

Yellow fever: an emerging threat for Kenya and other east African countries.

Yellow fever (YF) is a well known disease that had plagued the tropics relentlessly until an effective vaccine was developed. Although the yellow fever vaccine is relatively affordable and one dose protects for over ten years, its use has predominantly been for known endemic areas of the world and international travellers. Eastern and southern African states, have hitherto been free of epidemic yellow fever, hence routine YF vaccination is not a policy in these countries. The sudden emergence of YF in the Rift Valley in Kenya in 1992-1993, introduces new dimensions into the challenges of YF to eastern and southern African states. Isolation of a virus deemed to be native of the area is discussed in this article in the context of YF policy issues confronting the region. A case has been argued for the establishment of a network of active surveillance systems in the region backed by adequate laboratory YF expertise locally, regionally, and internationally.

Serological investigation of HIV-1 variant subtype strains in transmission in Nairobi.

In a bid to determine the HIV-1 subtype variants in transmission in Nairobi and its possible association with clinical status, we screened 207 confirmed HIV-1 positive patients visiting HIV/AIDS laboratory at the Virus Research Centre in Nairobi between January and March 1994. We used a selfmade ELISA obtained from an established panel of HIV-1 V3 loop peptides (ANRS, France) and derived from seven isolates: MN, HXB2, SC, Z6, Z2, ELI and CDC4. Test samples were obtained from 95 blood donors and medical examination attendees, 57 patients with chronic diarrhoea, 31 confirmed pulmonary tuberculosis, 16 with pneumonia and 12 herpes zoster. Out of the total, 21.5% had antibodies against the MN strain, 19.1% had against the Z2 strain while reaction against the HXB2 strain was observed in 17.2%. SC, CDC4, Z6 and ELI had prevalences of 11.5%, 6.2%, 5.3% and 3.8% respectively. Fifteen per cent of the tested sera showed no reaction to any of the used peptides. Strong and significant associations were observed between the total number of strains a sample react to and the clinical state. We infer that both the North American consensus strains (MN and HXB2) and the African isolates (Z2 and Z6) are predominant in Nairobi. The correlation between antibody reactivity and clinical state is an interesting observation that necessitates an expanded study and, the use of strain specific peptides maybe a sensitive and easier method for use for molecular epidemiological purposes.

PIP: During January-March 1994, in Nairobi, Kenya, the sera of pre-university students, suspected AIDS/advanced HIV-infection cases, and blood donors were screened for HIV-1 antibodies at the Virus Research Centre. All confirmed HIV-1 positive samples were categorized according to the patient's clinical status. A self-made ELISA was obtained from an established panel of HIV-1 V3 loop peptides and derived from seven isolates (MN and HXB2 [North American strains], SC, CDC4, Z2 and Z6 [African strains], and ELI). The sera of the 22 confirmed HIV-1 negative students were used as negative controls. There were 207 confirmed HIV-1 cases (95 blood donors and 112 suspected AIDS/advanced HIV-infection cases). 64 (31%) and 112 (54%) samples reacted to at least 3 strains and no more than 2 strains, respectively. The remaining 31 (15%) samples did not react to any of the 7 peptide strains. Samples with CD4 cell counts greater than 500 x 1 million reacted significantly to more peptide strains than those with CD4 counts below 200 x 1 million (88% vs. 7%). Reactivity to specific strains were 21.5% for MN, 19.1% for Z2, 17.2% for HXB2, 11.5% for SC, 6.2% for CDC 4, 5.5% for Z6, and 3.8% for ELI. Anti-HXB2 antibodies were more common in blood donors than suspected AIDS/advanced HIV-infection cases (22% vs. 13%). AIDS/advanced HIV-infection cases were more likely to have no antibodies than blood donors (21% vs. 7%). A significant association existed between the number of peptide strains a patient could react to and the clinical state (p 0.01). Specifically, 77% of samples with no V3 antibodies to the seven strains had AIDS or advanced HIV infection while 55% of those which had cross reactivity with three or more strains were asymptomatic. Further research is needed to better understand this correlation. These findings suggest that use of strain specific peptides may be a sensitive and easier method for use for molecular epidemiological purposes.

Measles trends and vaccine effectiveness in Nairobi, Kenya.

OBJECTIVES: To determine morbidity and mortality from measles and to estimate measles vaccine effectiveness among children hospitalised with measles in two hospitals in Nairobi. DESIGN: A review of hospital records (index cards). SETTING: Kenyatta National Hospital and Mbagathi District Hospitals covering the years 1996-2000. METHOD: A review of index cards for measles morbility and mortality was undertaken in the two hospitals. Measles data at the Kenya Expanded Programme on Immunisation covering both hospitals was analysed for vaccine effectiveness. RESULTS: The incidence of measles was unusually high in 1998 between July and November (monthly range 130-305), reflecting on the occurrence of an outbreak at that time. There was no definite monthly incidence trend of measles in 1996,1997, 1999 and 2000. The median age of cases was 13 months (range 0-420 months) for Kenyatta hospital and 18 months (range 1-336 months) for Mbagathi Hospital. Significantly, 29.8% of all cases were aged below nine months when routine immunisation for measles had not begun. The median number of days spent in hospital were five days (range 0-87 days) for Kenyatta and four days (range 1-13 days) for Mbagathi. The overall case fatality rate was 5.6% and was similar for both males and females. The overall measles vaccine effectiveness among measles cases admitted to Kenyatta and Mbagathi Hospitals was 84.1%. CONCLUSION: The case admissions in Kenyatta and Mbagathi Hospitals suggest measles was prevalent in Nairobi over the latter half decade of the 1990's. Apart from 1998 when there was an outbreak, the seasonality of measles was dampened. The 1998 outbreak suggests a build up of susceptible children the majority of whom were born in the last quarter of 1996. The high mortality may have had to do with the majority of cases presenting late when symptoms were already complicated and severe.

Efficacy of hepatitis B vaccine in a rural community in Muranga, Kenya.

One hundred and seventy four high risk cases were vaccinated at Muranga district in Kenya. The plasma derived HB vaccine was used in 61 cases (group 1) and recombinant HB vaccine was used in 113 cases (group 2). Fifty five cases (90.2%) in group 1 and 112 (99.1%) cases in group 2 seroconverted. Anti-HBc seroconversion occurred in one case during the study period. Significant anti-HBs seroconversion were obtained both for plasma derived HB vaccine and recombinant HB vaccine. In infants, there was statistically significant difference between the geometrical mean of anti HBs titres in group 1 and that in group 2. The recombinant vaccine was more effective than the plasma derived vaccine.

A community based longitudinal study of viral hepatitis B in a rural community.

Community based longitudinal epidemiological study of hepatitis B virus (HBV) was done in Maragua between June 1986 and November 1987. Hepatitis B surface antigen (HBsAg) carrier rate in the community was 3%. The high risk groups of HBV infection in the community were members of HBV carrier families and babies born to highly infectious mothers. Horizontal transmission of HBV at school did not seem to be very important.

Seroepidemiological study for HBV markers and anti-delta in Kenya.

An HBV carrier rate of 3.0% in outpatients and 1.4% in school children, was found in a sero-epidemiological survey in Muranga District, Kenya. The prevalence of anti-Delta in HBV carriers was 42%. The prevalence of HBV carriers and HBV marker positive cases was high in family members of HBV carriers. The yearly attack ratio of HBV was low in primary school children, non-carrier family members and even carrier family members. Mother to baby vertical transmission was very high when mothers were HBeAg positive HBV carriers. Such vertical transmission may now be of major importance.

Human plasma derived hepatitis B vaccine: Kenyan experience.

OBJECTIVE: To determine the efficacy and safety of hepaccine B. DESIGN: Vaccination on first-come-first-served basis. SETTING: Kenya Medical Research Institute (KEMRI) staff and families at Nairobi, Kenya. PARTICIPANTS: A total of 107 vaccinees aged 0-10 years and 10 years and above. MAIN OUTCOME: Antibody to hepatitis B surface antigen (anti HBs) checked one month after the third dose of the vaccine. RESULTS: Ninety seven per cent of the vaccinees developed antiHBs. Side effects were few in the form of soreness at site of injection and headache. CONCLUSION: Hepaccine B produced good immune response in vaccinees with minimal side effects.

CD4T lymphocyte subsets and disease manifestation in children with and without HIV born to HIV-1 infected mothers.

OBJECTIVE: To understand the natural history of HIV-1 infection in children in terms of evolution of childhood clinical manifestations versus the immune status, we prospectively studied children with and without maternally transmitted HIV-1 infection born to mothers infected with HIV-1 for two years between March 1998 and March 2000. DESIGN: A prospective cohort study. SETTING: An institutional children's home. SUBJECTS: Fifty nine children (26 males and 33 females) with and without maternally transmitted HIV-1 infection born to mothers infected with HIV-1 and adopted in institutional children home. METHODS: HIV-1 status of children under nine months was confirmed by polymerase chain reaction(PCR). ELISA for HIV-1 antibody in serum/plasma was used to confirm HIV-infection status for children aged < or = 18 months. Children were visited every three months between March and June 2000. At every visit blood was collected for total white cell count, haemoglobin and CD4+ and CD8+ T cell counts. The institutional doctor routinely examined children and treated all ailments. Clinical data were recorded. MEASURES: HIV-DNA, anti-HIV antibodies, total white blood count, total T cell counts, CD4 and CD8 T cell subset counts, frequency of childhood manifestations of infection. RESULTS: The children were aged between 4.5 and 13 years. The baseline haematological and immunological profiles (mean, mode) were: HIV-1 sero-converters (WBC 7151,7150; HB 11.6, 12.0; CD4+ 686, 795; CD8+ 2168, 1507) and HIV-1 de-seroconverters (mean, mode) were: (WBC 8386, 7150; HB 11.7, 12.8; CD4+ 735, 795; CD8+ 2168, 1507). The commonest causes of illnesses among the HIV-1 children were URTI (85.3%), TB(56.1 %), pneumonia (56.2%), tonsillitis (34.1%), parotiditis (28%) and acute otitis media (25%). The distribution of clinical manifestations was similar between the two categories of children, except URTI, whose prevalence was significantly increased among HIV-1 infected children (p-value=0.006). Among the HIV-1 infected children, only TB, parotiditis, and acute otitis media (AOM) were significantly associated with decreased CD4+ T cell count (p<0.05) resulting from HIV infection. CONCLUSIONS: HIV infection in children predisposes them to common childhood infections that can be used as markers of immune decline. TB, AOM, URTI may be early indicators of suspicion that would enable selective screening for HIV infection in children.

KEMRI Hep-cell II hepatitis B surface antigen screening kit.

BACKGROUND: Kenya is a high hepatitis B virus (HBV) endemic zone. Prevention of HBV transmission by transfusing safe blood is necessary. Kits for screening hepatitis B surface antigen (HBsAg) are usually imported and are expensive. Hence it has been difficult to screen donated and patient blood samples all over Kenya. OBJECTIVE: To produce a HBsAg screening kit locally in order to be able to screen donated and patient blood samples all over Kenya. DESIGN: A laboratory based study. SETTING: Centre for Virus Research (CVR), Kenya Medical Research Institute (KEMRI), Nairobi. METHOD: Purified HBsAg from plasma of carriers obtained from National Public Health Laboratories Services (NPHLS) was used to minimise guinea pigs to produce antihepatitis B (anti HBs) antibody. The anti HBs was then used to sensitise sheep red blood cells (SRBC). The final product was freeze dried (lyophilised) and its sensitivity and specificity was compared with other commercial kits. RESULTS: The sensitivity and specificity of KEMRI Hep-cell II was found to be 98% and 99%, respectively. The kit was found to be stable and potent for one year whether kept 4 degrees C, 37 degrees C or room temperature. CONCLUSION: KEMRI Hep-cell II was successfully produced locally. The sensitivity and specificity were comparable to other commercial kits. The kit was stable and potent for one year between temperature of 4 degrees C and 37 degrees C. The kit required only simple apparatus to carry out the test hence it can be used anywhere in Kenya. It was also cheap and affordable.

PIP: Kenya is a high hepatitis B virus endemic zone, and prevention of viral transmission by transfusing safe blood is necessary. However, kits for screening hepatitis B surface antigen (HBsAg) are usually imported and are expensive; hence, it has been difficult to screen donated and patient blood samples all over the country. This laboratory-based study, conducted at the Kenya Medical Research Institute (KEMRI), produced a HBsAg screening kit locally in order to be able to screen donated and patient blood samples throughout Kenya. Purified HBsAg from plasma carriers obtained from the National Public Health Laboratories Services was used to induce guinea pigs to produce anti-hepatitis B antibody (anti-HBs). The anti-HBs was then used to sensitize sheep red blood cells. The final product was freeze dried (lyophilized) and its sensitivity and specificity was compared with other commercial kits. The KEMRI Hep-cell II had 98% and 99% sensitivity and specificity, respectively, in comparison with other commercial kits. The kit was found to be stable and potent for 1 year at temperatures of 4 degrees Celsius, 37 degrees Celsius, or at room temperature. The KEMRI Hep-cell II kit is cheap and affordable and requires a simple apparatus to carry out the test; hence, it can be used anywhere in Kenya.

Maternal immune responses and risk of infant infection with HIV-1 after a short course Zidovudine in a cohort of HIV-1 infected pregnant women in rural Kenya.

OBJECTIVE: To investigate the effects of short-course nucleoside reverse transcriptase inhibitor (Zidovudine, ZDW/AZT) on maternal immune responses and risk of infant infection with HIV-1 among rural-based mothers in western Kenya. DESIGN: A prospective cohort study involving HIV-1 seropositive pregnant mothers and their infants. SUBJECTS: One hundred and seven HIV-1 seropositive asymptomatic pregnant women and their infants. METHODS: After informed consent, the women were enrolled at gestation age between 16-24 weeks. For cultural and economic reasons, all mothers were allowed to breast feed their infants. Short-course antepartum regime of AZT was administered to all mothers starting at 36 weeks gestation until start of labour. Maternal absolute CD4+ T cell subset assays were performed before 3rd trimester (about 36 weeks gestation) and after a 4-week therapy of AZT (at least one month post-nuptially). Infant HIV-1 status was determined by HIV-1 DNA polymerase chain reaction (PCR) on samples sequentially taken at 1, 2, 3, 4, 6 and 9 months and confirmed by serology at 18 months of age. INTERVENTIONS: Antepartum short-course orally administered AZT: 300mg twice-daily starting at 36 weeks gestation until start of labour, 300mg at labour onset and 300mg every three hours during labour until delivery. MAIN OUTCOME MEASURES: Maternal CD4+ T cell counts before and after AZT treatment. Determination of infant HIV-1 infection status. RESULTS: Among 107 women sampled, only 59 received full dose of AZT and thus qualified for present analysis. Of these, 12 infected their children with HIV, while 47 did not. Comparison of CD4+ T cells before and after AZT treatment scored a significant rise in all mothers (P = 0.01). This increase in CD4+ T cells was not significant among mothers who infected their infants with HIV-1 (P = 0.474). However, a significant rise in CD4+ T cells following AZT therapy was observed only in mothers who did not transmit HIV-1 to their infants (P=0.014). CONCLUSION: These data suggest that a rise in the CD4+ T cell counts following short AZT regimen, now widely in use in resource-weak countries, may be evidence of the active suppression of the replication of HIV. However, further studies to examine the multi-factorial effect of CD4+ lymphocytes and pregnancy on MTCT of HIV need to be carried out to help fully explain the effect of AZT on immune response and whether the CD4+T cell count can be used as a true test of immunological normalisation during antiretroviral therapy.