Group B Streptococcus infection causes an estimated 150,000 preventable stillbirths and infant deaths every year
Press release issued: 6 November 2017
An estimated one in five pregnant women around the world carry Group B Streptococcus (GBS) bacteria which is a major, yet preventable, cause of maternal and infant ill health globally.
These are the findings of a new research supplement published in the journal Clinical Infectious Diseases, and launched at the American Society of Tropical Medicine and Hygiene Annual Meeting in Baltimore.
Led by the London School of Hygiene & Tropical Medicine and involving more than 100 researchers from around the world, including Professor Marianne Thoresen from the Bristol Medical School at the University of Bristol, the series of 11 research papers conservatively estimates that out of 410,000 GBS cases every year, there will be at least 147,000 stillbirths and infant deaths globally. Despite being home to only 13 per cent of the world’s population, Africa had the highest burden, with 54 per cent of estimated cases and 65 per cent of stillbirths and infant deaths.
This first comprehensive study of the burden of GBS, funded by a grant from the Bill & Melinda Gates Foundation, includes data and estimates for the year 2015 from every country of the world, including outcomes for pregnant women, their babies and infants. Previous data on GBS burden focused on infant cases and high-income countries, but the impact of GBS disease worldwide, especially in Asia, was less clear.
The new research found GBS is present among pregnant women in all regions of the world, with an average of 18 per cent of pregnant women worldwide carrying (colonised with) the bacteria, ranging from 11 per cent in eastern Asia to 35 per cent in the Caribbean, totalling 21.7 million in 195 countries
The top five countries by numbers (to nearest 100) of pregnant women colonised were: India (2,466,500) China (1,934,900), Nigeria (1,060,000), United States of America (942,800) and Indonesia (799,100).
Although several vaccines to prevent GBS are in development, none is currently available. This is despite the disease accounting for more than the combined neonatal deaths from tetanus, pertussis, and respiratory syncytial virus, for which maternal vaccines are already in use, or further advanced in development. This analysis shows for the first time that a maternal GBS vaccine, which was 80 per cent effective and reached 90 per cent of women, could potentially prevent 231,000 infant and maternal GBS cases.
GBS is carried by up to a third of adults, usually with no symptoms. In women, GBS can live harmlessly in the digestive system or lower vaginal tract, from where it can be passed to the unborn baby through the amniotic fluid or to newborns during labour. Babies are more vulnerable to infection as their immature immune systems cannot fight off the multiplying bacteria. If untreated, GBS can cause serious infections, such as meningitis and septicaemia, which may lead to stillbirths, and newborn and infant deaths. If they survive, babies can develop permanent problems including hearing or vision loss, or cerebral palsy.
Current GBS prevention focuses on giving antibiotics to women in labour, aiming to reduce disease in infants at delivery. At least 60 countries have a policy for antibiotic use in pregnancy to prevent newborn GBS disease. Of those, 35 have a policy to test all pregnant women to see if they carry GBS, and the remaining 25 countries identify women with clinical risk factors. However, implementation of these policies varies around the world.
Joy Lawn, Series co-lead and Professor of Maternal, Reproductive and Child Health at the London School of Hygiene & Tropical Medicine, said: "Too many parents around the world face the death of a baby or a young child – avoidable GBS deaths are happening in every country. Antibiotics currently prevent an estimated 29,000 cases of early-onset Group B Streptococcal disease per year, almost all in high-income settings. However, this approach may be difficult in low-income settings where many births take place at home, and laboratory capacity for screening for GBS is limited. In addition, giving antibiotics to 21.7 million women may contribute to antimicrobial resistance – a major global health crisis."
Anna Seale, Series co-lead and Associate Professor at the London School of Hygiene & Tropical Medicine said: "Even if antibiotics were given to all pregnant women identified through screening strategies, they target mainly early-onset GBS disease in newborns, not GBS disease in pregnant women, GBS disease before delivery causing stillbirth, or GBS disease in infants more than a couple of days old. A maternal GBS vaccine could prevent many more cases and deaths worldwide."
Dr Keith Klugman, Director of the Pneumonia Team at the Bill & Melinda Gates Foundation, said "The first few days and weeks of a baby's life are the most vulnerable - by far. By filling in one of the great voids in public health data, this work provides crucial insight and shows the pressing unmet need for the development of an effective Group B Strep vaccine. Immunizing expectant mothers is a potentially ground-breaking approach that could dramatically reduce the number of maternal and child deaths."
Johan Vekemans, co-author and Medical Officer, Initiative for Vaccine Research, World Health Organization, said: "These disease burden estimates highlight the importance of perinatal infection prevention. Existing recommendations should be implemented, but these are insufficient, and the number of affected families remain unacceptable. It is now essential to accelerate the GBS vaccine development activities. The technical feasibility is estimated to be high. Guidance highlighting research priorities is available. Work is ongoing to strengthen existing maternal immunization programmes. Next steps include a comprehensive evaluation of cost-effectiveness. We will be working with Professor Lawn and others at London School of Hygiene & Tropical Medicine, and global partners to lead on these activities."
Technical note on estimates: Although the team were able to more than double the previously available data through the many authors and institutions involved, and aimed to minimise bias where possible, and to describe and analyse the direction of bias where it was identified, modelling studies cannot overcome a lack of data. Some evidence was found of GBS being a risk factor for preterm birth, and GBS could contribute to up to 3.5 million preterm births each year, but this evidence was impeded by variations in study designs. The researchers also highlight the need for more follow-up studies to examine disability, especially beyond five years of age, and more data regarding stillbirths especially from Asia. Hence, these estimates of maternal GBS disease, stillbirths, and infants with invasive GBS disease are all likely to be underestimates.
Clinical Infectious Diseases Group B Streptococcus research supplement study group:
Joy Lawn, Anna C Seale, Fiorella Bianchi-Jassir, Neal J. Russell Maya Kohli-Lynch, Cally J. Tann, Jennifer Hall, Lola Madrid
Clinical Infectious Diseases Group B Streptococcus research supplement Expert Advisory Group:
Carol J. Baker, Linda Bartlett, Clare Cutland, Michael G. Gravett, Paul T. Heath, Margaret Ip, Kirsty Le Doare, Shabir A. Madhi, Craig E. Rubens, Samir K. Saha, Stephanie Schrag, Ajoke Sobanjo-ter Meulen Johan Vekemans
Declaration of conflict of interest:
Authors and members of the Expert Advisory Group’s declaration of potential conflicts of interest can be found in each paper.
About the London School of Hygiene & Tropical Medicine
The London School of Hygiene & Tropical Medicine is a world-leading centre for research and postgraduate education in public and global health, with more than 4,000 students and 1,000 staff working in over 100 countries. The School is one of the highest-rated research institutions in the UK, is among the world's leading schools in public and global health, and was named University of the Year in the Times Higher Education Awards 2016. Our mission is to improve health and health equity in the UK and worldwide; working in partnership to achieve excellence in public and global health research, education and translation of knowledge into policy and practice. http://www.lshtm.ac.uk