Coverage and efficacy of BCG vaccination in displaced populations: a measure of effectiveness of an Expanded Programme of Immunization

Abstract

Growing numbers of refugees and internally displaced populations (IDPs) and their health problems are creating a need to continuously assess and modify preventive interventions, including immunization programmes, to suit evolving needs. Infants and young children are the most commonly affected by nutritional and infectious diseases leading to about 15 million annual deaths. Mycobacterial infections, particularly tuberculosis, are important causes of morbidity and mortality among refugees and internally displaced people. BCG vaccination protects against disseminated childhood tuberculosis and may reduce child mortality in Africa. Assessment of BCG efficacy is difficult and gives widely variable results. This study aimed at assessing BCG coverage and efficacy among internally displaced children in Sudan, so as to modify BCG vaccination schedules to suit this population, if needed. Following parent/guardian informed consent, eight hundred and twenty eight healthy children ≤ 5 years were enrolled in the study. BCG coverage was assessed using vaccination card checking and scar rate, while BCG efficacy was assessed by injecting 5 TU PPD intradermally and reactivity was measured after 48-72 hours. Card checking put BCG coverage at 83%, while BCG scar rate was 92%. Thirty-three per percent had Mantoux reading of ≥5 mm with a mean Mantoux induration of 4.2 mm (±5.32SD). Skin non-reactivity was higher in the older age groups. Non-reactive Mantoux was higher among Nuba tribes of Kordofan as compared to other ethnic groups. There was no correlation between this high non- reactivity rate and the nutritional status. Increased skin non-reactivity in infants could be explained by immaturity of the immune system; but no explanation could be found for this phenomenon in other age groups. The high skin non-reactivity may indicate a need for re-vaccination as practiced elsewhere. In conclusion, the current BCG vaccine schedule in Sudan has adequate coverage, but may need to be modified to include revaccination so as to obtain better protection and reduce infant mortality especially in IDPs. The probable explanation for high negative Mantoux reactivity may be due to differences in ethnicity. There is also a need to introduce alternative techniques to assess BCG efficacy under field conditions.