The implementation of the Expanded Program of Immunization (EPI) in 1989 has dramatic impact on hepatitis B virus (HBV) infection in school children in Malaysia. A cross-sectional seroprevalence study of HBV infection in 190,077 school children aged 7-12 years from 1997 to 2003 showed a steady decline of HBV surface antigen (HBsAg) prevalence rate from 2.5% for children born in 1985 to 0.4% among school children born in 1996. The overall prevalence of HBsAg was 0.6%, 0.7% in males and 0.6% in females. Over 92.7% of school children had been vaccinated with HBV vaccine, in which 93.7% were vaccinated under the EPI and 6.3% on voluntary basis. The school children vaccinated under EPI had a 0.4% HBsAg carrier rate, which was significantly lower than school children vaccinated on a voluntary basis (HBsAg carrier rate 1.3%) and non-vaccinated school children (HBsAg carrier rate 2.7%), suggesting that HBV vaccination of infants was the most effective measure in preventing vertical transmission of HBV in the hyperendemic region.
Earlier studies in the 1990s indicate that human immunodeficiency virus type 1 (HIV-1) subtype B has been the predominant subtype among injecting drug users (IDUs) in Malaysia. More recent studies performed between 2003 and 2004, however, show a high prevalence of unique CRF01_AE/B intersubtype recombinants among IDUs. To determine the subtype distribution among IDUs in Kuala Lumpur prior to the emergence of CRF01_AE/B intersubtype recombinants, the gag-pol or the reverse transcriptase gene was sequenced from IDUs who were diagnosed as HIV positive between 1993 and 2002. Subtype B was present at 50.0% followed by CRF01_AE/B recombinant at 41.7%, with more CRF01_AE/B recombinants detected between 2000 and 2002. All CRF01_AE/B recombinants shared similar recombination patterns. Interestingly, we found that this potential new candidate of circulating recombinant form (CRF) could have emerged as early as the mid-1990s. The results showed evidence of changing HIV-1 molecular epidemiology toward the predominance of CRF01_AE/B intersubtype recombinants among IDUs in Kuala Lumpur.
We investigated the molecular epidemiology of HIV-1 subtypes in Malaysia among injecting drug users (IDUs) and sexual transmission risk groups, using serologic and genetic techniques. Frozen sera collected at a general hospital, a blood bank, several drug treatment centers, and an STD clinic in Kuala Lumpur, between 1992 and 1996, were investigated retrospectively. V3 peptide serotyping and monomeric gp120 capture serotyping were used to study 89 known HIV-1-infected subjects. The methods differentiate subtypes B, E, and C. V3 peptide and gp120 capture results were comparable. No subtype C-specific reactive sera were found; one specimen was dually reactive for subtypes C and B, using the V3 peptide ELISA; and four were durally reactive for subtypes E and C using this assay. Genotypic analysis of HIV-1 gag RNA in serum was done on a subset of subjects and confirmed serologic findings. HIV-1 subtypes differed significantly by risk category: of 53 IDUs, 29 (55%) were infected with subtype B and 19 (36%) were infected with subtype E, 3 (6%) were dually reactive, and 2 (4%) were not typable. Of 36 persons with heterosexual risks, 29 (81%) were infected with subtype E, 5 (14%) were infected with subtype B, and 2 (5%) were not typable. Persons with IDU risks were significantly more likely to be infected with subtype B than were those with sexual risks (OR 5.89; 95% CI, 1.94-18.54; p < 0.001). Subtypes B and E of HIV-1 appear to predominate in Malaysia; subtype B was more prevalent among IDUs; subtype E was more prevalent among all other groups. These results may have important HIV-1 vaccine implications.
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