The Gambia Government, through the Ministry of Health and Social Welfare, worked with the MRC Unit, The Gambia and partners including the London School of Hygiene & Tropcial Medicine on the study. It is the first to demonstrate the real-life impact of pneumococcal conjugate vaccines (PCV) in a low-income country. Reducing the rate of pneumococcal disease is crucial, both to save lives and reduce a substantial economic burden on the health system and families.
The researchers found that in The Gambia, routine infant PCV vaccination successfully reduced severe pneumococcal diseases, including pneumonia, sepsis, and meningitis in children aged 2-23 months by 55%, with a 56% reduction in children aged 2-4 years. The data generated will facilitate the introduction and maintenance of PCVs in other countries in Africa, where the rate of pneumococcal disease is ten times higher than in developed countries.
Pneumococcal disease is caused by infection with the bacterium Streptococcus pneumoniae. Symptoms range from sinus and ear infection to potentially fatal pneumonia, sepsis and meningitis; children in The Gambia who develop invasive pneumoccal diseases have a one in seven chance of dying. This eight-year study used robust population surveillance methods before and after introduction of two PCVs to measure the impact of routine infant vaccination with these vaccines.
14,650 children and adults were monitored for signs of pneumonia, sepsis, and meningitis during the course of the study in Basse, The Gambia, where the UK MRC has a field station. The first seven-valent PCV was introduced in August 2009 as part of the Gambian Expanded Programme on Immunisation (EPI) and a second 13-valent PCV, active against more pneumococcal strains, in 2011 The vaccines were given to children in a schedule of three doses at two, three and four months of age. A total of 320 cases of invasive pneumococcal disease were identified during follow-up period.
Although these findings are encouraging, there is a need for continued advocacy for PCV in low-income countries that have not yet introduced the vaccine. The results should reassure developing countries that spending money on PCV, and delivering the vaccine with reasonable coverage, will substantially reduce rates of pneumococcal disease.
Study author Sir Brian Greenwood, Professor of Clinical Tropical Medicine at the London School of Hygiene & Tropical Medicine, who has worked for more than 30 years on pneumococcal vaccines in The Gambia, said: “This will be welcome news to the many developing countries that have invested in the introduction to PCV, and also to the Global Alliance for Vaccines and Immunization (GAVI) which has supported them financially. PCV have the potential to save many young lives in the developing world, and the outcome of this well conducted study will help sustain investment in this vaccine.
“However, it is still too early to judge the long-term effectiveness of PCV on young children, and on the wider community, in poorly resourced countries, and further long-term follow-up of the impact of PCV in these countries is essential.”
This publication derives from the work of the Pneumococcal Surveillance Project (PSP) based at the MRC Unit, The Gambia. This project is funded by the Global Alliance for Vaccines and Immunisation’s Pneumococcal Vaccines Accelerated Development and Introduction Programme, the Bill & Melinda Gates Foundation, and the Medical Research Council, UK; and is led by Principal Investigator, Dr Grant Mackenzie.
The pneumococcal vaccine impact study was conducted in collaboration with the Ministry of Health and Social Welfare, The Gambia; Medical Research Council (UK); London School of Hygiene & Tropical Medicine; University of Otago; International Vaccine Access Centre at Johns Hopkins University; Murdoch Childrens Research Institute, Melbourne; and the Program for Appropriate Technology in Health, Seattle.
Grant A. Mackenzie et al. (2016) Effect of the introduction of pneumococcal conjugate vaccination on invasive pneumococcal disease in The Gambia: a population-based surveillance study, The Lancet Infectious Diseases, DOI: http://dx.doi.org/10.1016/S1473-3099(16)00054-2
Image credit: MRC Unit, The Gambia
London School of Hygiene & Tropical Medicine