Safety monitoring of a pentavalent vaccine in the expanded programme on immunisation in Ghana

Background and objective: Safety monitoring of vaccines used in expanded programmes on immunisation is important in all countries, including those with limited resources. As the rates of target diseases decrease, parents become less accepting of even minor common adverse events. Identification, detection, prevention and appropriate communication of adverse events following immunisation (AEFI) are therefore essential to preserve the integrity of immunisation programmes and protect public health. The objective of this study was to document the occurrence of common minor AEFI associated with a newly introduced pentavalent vaccine for routine immunisation in Ghana's expanded programme on immunisation. Methods: A prospective descriptive study on AEFI associated with the administration of a pentavalent diphtheria, tetanus, pertussis, hepatitis B and Haemophilus influenzae type B (DTP-hepatitis B vaccine/Hib vaccine) vaccine that is part of the Expanded Programme on Immunisation was carried out in four locations in Accra, Ghana. These locations were the nation's premier teaching hospital (the Korle-Bu Teaching Hospital) two urban polyclinics (the Mamprobi and Ussher Town polyclinics) and a community immunisation centre (the Zongo Junction Immunisation Centre). A total of 406 infants were recruited for the study. Upon receipt of signed informed consent from the parents/guardians of the infants, the parents/guardians were supplied with a pink card that functioned as a pseudo-diary for recording AEFI that occurred at home and for measuring and noting the sizes of any injection-site swellings that might occur. It also enabled each participant to obtain free medical care at the Department of Child Health, Korle-Bu Teaching Hospital for the duration of the study (from September 2003 to December 2004) and until the child was 12 months old. Information about the occurrence of AEFI was actively solicited during each visit for immunisation and also at a visit 4 weeks after administration of the last dose of pentavalent vaccine, when participants were asked to report to the respective immunisation centres for the specific purpose of reporting any AEFI which might have occurred in the intervening period. These AEFI were analysed separately from those reported to the dedicated hospital unit at the Department of Child Health, Korle-Bu Teaching Hospital, since the AEFI reported to that unit were all verified and recorded by trained physicians. Results: Of the 406 infants, 368 completed the study, whereas 38 defaulted or were lost to follow-up. There were 104 attendances to report cases of suspected AEFI requiring physician attention at the Department of Child Health, Korle-Bu Teaching Hospital. These attendances were made by 74 patients who reported 190 events; notable among these were cough (26.3% of all AEFI reported to the hospital), fever (17.4%), common cold (12.1%), vomiting (7.4%) and diarrhoea (6.8%). Three of these visits involved AEFI that were classified as 'serious', since they required hospitalisation, but all three were considered to be unlikely to be related to vaccine administration. In addition, actively solicited information on AEFI following immunisation from 921 individual interviews with the parents/guardians of immunised infants during the follow-up visits resulted in reports of 259 events being reported, the most common, according to crude incidence rates, being fever (14.7%), common cold (3.8%), crying (3%) and cough (2.8%). Conclusion: The results of this study show agreement with safety studies on vaccines containing identical or similar antigens performed elsewhere and indicate the safety and tolerability of the pentavalent DTP-hepatitis B vaccine/Hib vaccine in Ghanaian children.