title: HIV-Infected or -Exposed Children Exhibit Lower Immunogenicity to Hepatitis B Vaccine in Yaoundé, Cameroon: An Appeal for Revised Policies in Tropical Settings?
abstract: BACKGROUND
  Since 2005, anti-hepatitis B virus (anti-HBV) vaccine is part of the Expanded Program on Immunization (EPI) for infants born in Cameroon, with 99% anti-HBV coverage. In a context of generalized HIV epidemiology, we assessed paediatric anti-HBV vaccine response according to HIV status, feeding option and age in a tropical context.
  
  
  METHODS
  Prospective, observational and cross-sectional study conducted among 82 children (27 [IQR: 9-47] months, min-max: 6-59), after complete anti-HBV vaccination (Zilbrix Hepta: 10μg AgHBs) at the Essos Health Centre in Yaounde, Cameroon, classified as group-A: HIV unexposed (28), group-B: HIV-exposed/uninfected (29), group-C: HIV-infected (25). Quantitative anti-HBs ELISA was interpreted as "no", "low-" or "protective-response" with <1, 1-10, or ≥10 IU/L respectively; with p-value<0.05 considered significant.
  
  
  RESULTS
  Children were all HBV-unexposed (AcHBc-negative) and uninfected (HBsAg-negative). Response to anti-HBV vaccine was 80.49% (66/82), with only 45.12% (37/82) developed a protective-response (≥10IU/L). According to HIV status, 60.71% (17/28) developed a protective-response in group-A, vs. 51.72% (15/29) and 20% (5/25) in group-B and group-C respectively, Odds Ratio (OR): 2.627 [CI95% 0.933-7.500], p = 0.041. According to feeding option during first six months of life, 47.67% (21/45) developed a protective-response on exclusive breastfeeding vs. 43.24% (16/37) on mixed or formula feeding, OR: 1.148 [CI95% 0.437-3.026], p = 0.757. According to age, protective-response decreased significantly as children grow older: 58.33% (28/48) <24 months vs. 26.47% (9/34) ≥24 months, OR: 3.889 [CI95% 1.362-11.356], p = 0.004; and specifically 67.65% (23/34) ≤6 months vs. 0%, (0/5) 33-41 months, p = 0.008.
  
  
  CONCLUSIONS
  Anti-HBV vaccine provides low rate of protection (<50%) among children in general, and particularly if HIV-exposed, infected and/or older children. Implementing policies for early vaccination, specific immunization algorithm for HIV-exposed/infected children, and monitoring vaccine response would ensure effective protection in tropical settings, pending extensive/confirmatory investigations.
authors.affiliation: Pediatric Service, National Insurance Fund Welfare Hospital, Yaoundé, Cameroon.|Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaoundé, Cameroon.
authors.forename: Anne Esther
authors.initials: AE
authors.lastname: Njom Nlend
authors.affiliation: Higher Institute of Health Professions, Yaoundé, Cameroon.|Ministry of Public Health, Yaoundé, Cameroon.|Institute of Science and Technology Applied to Health, Yaoundé, Cameroon.
authors.forename: Philippe Salomon
authors.initials: PS
authors.lastname: Nguwoh
authors.affiliation: Institute of Science and Technology Applied to Health, Yaoundé, Cameroon.
authors.forename: Christian Taheu
authors.initials: CT
authors.lastname: Ngounouh
authors.affiliation: Bambino Gesu Paediatric Hospital, Rome, Italy.
authors.forename: Hyppolite Kuekou
authors.initials: HK
authors.lastname: Tchidjou
authors.affiliation: Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaoundé, Cameroon.|Higher Institute of Health Professions, Yaoundé, Cameroon.
authors.forename: Constant Anatole
authors.initials: CA
authors.lastname: Pieme
authors.affiliation: Higher Institute of Health Professions, Yaoundé, Cameroon.
authors.forename: Jean Mbede
authors.initials: JM
authors.lastname: Otélé
authors.affiliation: Higher Institute of Health Professions, Yaoundé, Cameroon.|Department of Biochemistry and Microbiology, Faculty of Science, University of Yaoundé 1, Yaoundé, Cameroon.
authors.forename: Véronique
authors.initials: V
authors.lastname: Penlap
authors.affiliation: Chantal BIYA International Reference Centre for Research on HIV/AIDS prevention and management, Yaoundé, Cameroon.|University of Rome Tor Vergata, Rome, Italy.|UNESCO Interdisciplinary Board of Biotechnology, Rome, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Colizzi
authors.affiliation: Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaoundé, Cameroon.|Chantal BIYA International Reference Centre for Research on HIV/AIDS prevention and management, Yaoundé, Cameroon.|Institute of Research in Medicine and Medicinal plants, Yaoundé, Cameroon.
authors.forename: Roger Somo
authors.initials: RS
authors.lastname: Moyou
authors.affiliation: Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaoundé, Cameroon.|Chantal BIYA International Reference Centre for Research on HIV/AIDS prevention and management, Yaoundé, Cameroon.|University of Rome Tor Vergata, Rome, Italy.
authors.forename: Joseph
authors.initials: J
authors.lastname: Fokam