International Journal of Epidemiology
Volume 43 Issue 3 June 2014
The non-specific effects of vaccines and other childhood interventions: the contribution of INDEPTH Health and Demographic Surveillance Systems
Osman Sankoh1,2,3,*, Paul Welaga1,4, Cornelius Debpuur1,4, Charles Zandoh1,5, Stephney Gyaase1,5, Mary Atta Poma1,6, Martin Kavao Mutua1,7, SM Manzoor Ahmed Hanifi1,8, Cesario Martins1,9, Eric Nebie1,10, Moubassira Kagoné1,10, Jacques BO Emina1 and Peter Aaby1,9
1INDEPTH Network, Accra, Ghana, 2School of Public Health, University of the Witwatersrand, Johannesburg, South Africa, 3Faculty of Public Health, Hanoi Medical University, Hanoi, Viet Nam, 4Navrongo Health Research Centre, Ghana Health Service, Navrongo, Ghana, 5Kintampo Health Research Centre, Ghana Health Service, Kintampo, Ghana, 6Dodowa Health Research Centre, Ghana Health Service, Dodowa, Ghana, 7African Population and Health Research Centre, Nairobi, Kenya, 8Chakaria Community Health Project Community Health Division, ICDDRB, Mohakhali, Dhaka, Bangladesh, 9Bandim Health Project, Bandim, Guiné-Bissau and 10Centre de Recherche en Santé de Nouna (CRSN), Nouna, Burkina Faso
Accepted April 3, 2014.
Most childhood interventions (vaccines, micronutrients) in low-income countries are justified by their assumed effect on child survival. However, usually the interventions have only been studied with respect to their disease/deficiency-specific effects and not for their overall effects on morbidity and mortality. In many situations, the population-based effects have been very different from the anticipated effects; for example, the measles-preventive high-titre measles vaccine was associated with 2-fold increased female mortality; BCG reduces neonatal mortality although children do not die of tuberculosis in the neonatal period; vitamin A may be associated with increased or reduced child mortality in different situations; effects of interventions may differ for boys and girls. The reasons for these and other contrasts between expectations and observations are likely to be that the immune system learns more than specific prevention from an intervention; such training may enhance or reduce susceptibility to unrelated infections. INDEPTH member centres have been in an ideal position to document such additional non-specific effects of interventions because they follow the total population long term. It is proposed that more INDEPTH member centres extend their routine data collection platform to better measure the use and effects of childhood interventions. In a longer perspective, INDEPTH may come to play a stronger role in defining health research issues of relevance to low-income countries.
Commentary: Potential implications of non-specific effects of childhood vaccines
Harshpal Singh Sachdev
Department of Pediatrics and Clinical Epidemiology, Sitaram Bhartia Institute of Science and Research, B-16 Qutab Institutional Area, New Delhi 110016, India.
The World Health Organization states that: ‘A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins. The agent stimulates the body’s immune system to recognize the agent as foreign, destroy it, and ‘remember’ it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters’.1 This statement is in conformity with the usual scientific and lay perceptions that vaccines have only specific disease-protective effects. However, historically it has been suspected that Vaccinia2 and BCG vaccination3 confer protection against non-targeted infectious diseases. Emerging evidence suggests that vaccines can positively or negatively affect the resistance to other infectious diseases—the so-called non-specific effects of vaccines or non-specific immunomodulation by vaccines. The bulk of this evidence has been generated from Guinea-Bissau by researchers led by Peter Aaby. The current status of global evidence has been summarized by them in this issue of IJE4 and elsewhere.5 On this basis, they also suggest a new definition of vaccines: ‘A vaccine is a biological preparation that improves immunity to a particular disease and at the same …