Letters to the Editor

Indian Pediatrics 2000;37: 1027-1028

Frequency of Mother-to-Infant Transmission of Human Immunodeficiency Virus

The frequency of mother-to-infant (vertical) transmission of human immuno-deficiency virus (HIV) varies from country to country(1,2). During the period prior to the introduction of specific antiviral preventive intervention to reduce vertical transmission, the frequency was 14 to 33 per cent in Western European countries and the United States of America(1). In Kenya the reported rate was 43 per cent(2). In Thailand, in non-breastfed infants, vertical transmission occurred in only 19%(3). A recent literature search did not show any such data from India. Therefore, the early experience of vertical transmission documented in Vellore is presented here.

The background information on the pregnant women, the HIV antibody screening by enzyme immunoassay (EIA) and confirmation by western blot (WB) test and the prevalence of infection among them have been published earlier(4). The EIA test was done using commercially available kits (Vironostika HIV MixT from Organon Technika, Boxtel, Holland or Wellcozyme from Wellcome Diagnostics, Dartford, United Kingdom). The WB was also done using a commercial kit (Diagnostic Biotechnology, Singapore). Any serum reactive in EIA was retested in duplicate and any repeatedly (at least two times in 3 tests) reactive serum was tested by WB. A positive WB result was defined as the presence of at least one band corresponding to gag, env and pol gene translates of HIV-1(5).

Infants born during 1988 to 1993 to HIV infected women formed the study group. No intervention except counseling was applied to the mothers. One blood sample from each infant (either cord blood or susbsequent venous sample) was tested to confirm maternal infection by the presence of maternal antibody. The diagnosis of HIV infection in the infant was made at or soon after 15 months of age, by testing a blood sample in screening and confirmatory tests.

During the study period, 31 HIV infected pregnant women came to delivery, all normal vaginal. All mothers gave breast feeding to their infants, but we did not document the duration. Among the 31 infants born to HIV infected women, only 23 were available for follow up at 15 months of age. Among them, 15 were without HIV antibody, but 8 (35%) were positive in screening and confirmatory tests. Thus, the frequency of vertical transmission is 35 per cent (95% confidence interval 15 to 54%) in this study.

The sample size is relatively small. Moreover, 8 of 31 (26%) were lost to follow up. The probability of some of them being HIV infected was high, but no value could be assigned. For these reasons, the rate of 35 per cent gives only an approximate value for this region.

T. Jacob John,
Emeritus Scientist,
Indian Council of Medical Research,
439, Civil Supplies Godown Lane,
Kamalakshipuram, Vellore 632 002, India.
E-Mail: [email protected]

1. Report of a consensus workshop. Maternal factors involved in mother to child transmission of HIV 1. AIDS 1992; 5: 1019-1029.

2. Datta P, Embree JE, Kreiss JK, Ndinya-Achola JO, Braddick M, Temmerman M, et al. Mother to child transmission of HIV type 1. Report from Nairobi study. J Infect Dis 1994; 170: 1134-1140.

3. Shaffer N, Chuachoowang R, R, Mock PA, Bhadracow C, Siriwasin W, et al. Short course zidovudine for preventing perinatal HIV trans-mission in Bangkok, Thailand. A randomized controlled perinatal HIV transmission study. Lancet 1999; 353: 773-780.

4. John TJ, Bhushan N, Babu PG, Seshadri L, Balasubramanium N, Jasper P. Prevalence of HIV infection in pregnant women in Vellore region. Indian J Med Res (A) 1993; 97: 227-230.

5. O'Gorman MR, Weber D, Landis SE, Schoen-bach, VJ, Mittal M, Folds JD. Interpretive criteria of the western blot assay for sero-diagnosis of human immunodeficiency virus type 1 infection. Arch Pathol Lab Med 1991; 115: 26-30.