Paediatrics (RCH) - Theses
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ItemThe Introduction of hepatitis B vaccine in rural Vietnam( 2004)Vietnam, a nation of almost 80 million people with a high rate of chronic infection with the hepatitis B virus (HBV), is currently expanding its introduction of hepatitis B vaccine (HepB vaccine) for infants across the nation. This is occurring within an immunisation program widely commended for its high coverage and achievements in disease control. During 1997, HepB vaccine was introduced for a small proportion of infants in urban areas, using a locally manufactured product which had not previously been objectively evaluated in the field. In addition, the problem of HBV infection itself had not been adequately quantitated, making subsequent evaluation of the program difficult. To make HepB vaccine available more widely and at birth, as is needed to prevent the perinatal infection responsible for a large proportion of chronic HBV infection, its storage outside the cold chain has been suggested. This would enable its use for infants born in remote areas lacking access and refrigeration, but scientific verification of the vaccine's immunogenicity and protective efficacy (PE) when used in this way is lacking. In addition, it is not certain that birth dosing, nor indeed the three required doses of the vaccine itself will be acceptable to Vietnamese mothers, who are unused to infants receiving any vaccines before the age of two months and not unreasonably concerned about injection safety. In this thesis I examine the situation with respect to the conduct of the Expanded Program on Immunisation (EPI) in one rural province of central northern Vietnam, and community attitudes towards this program and the introduction of HepB vaccine. Grave concerns about the planning, safety, effectiveness and veracity of reporting of the Program are raised, and health worker and community education programs recommended prior to the introduction of birth dosing with HepB vaccine. I report on a survey of the seroprevalence of HBV infection in this location, confirming very high rates of perinatal infection and a monotonous increase in exposure with age. I also compare the immunogenicity of the locally produced vaccine in two different formulations with that of two internationally licensed Korean vaccines, concluding that the dose currently used in the Vietnamese EPI should be increased. I evaluate three different strategies for the introduction of HepB vaccine in varying geographic and demographic milieu, both scientifically in terms of their immunogenicity and PE, and for their operational feasibility and likely generalisability throughout Vietnam. I provide further evidence in support of the immunogenicity of HepB vaccine stored at ambient temperature, but only limited evidence relating to PE, probably because of the low dose of vaccine available. I compare the responses of local communities to differing levels of dissemination of information relevant to the introduction of HepB vaccine, and of health workers to training to improve their conduct of the EPI. Improving the EPI, including introduction of HepB vaccine with a birth dose, seems both feasible and acceptable to all concerned. Finally, I evaluate the activities conducted by examining changes in the prevalence of two objectively measurable indicators of the conduct of the EPI. Whilst rates of scars following bacille Calmette-Guerin vaccine increased substantially, rates of immunity to measles amongst older infants did not.