By Victoria Ponce, MARCH centre
Research showing the worldwide Group B Streptococcus (GBS) burden in pregnant women, stillbirths and children is being launched today, Monday 6th of November, at the annual American Society of Tropical Medicine & Hygiene in Baltimore, USA. The research involved over 100 researchers from more than 30 institutions and was coordinated by the MARCH Centre at LSHTM.
The research found that GBS affects all regions of the world. Globally, 21.7 million pregnant women carry the GBS bacteria, which translates to a global average of 18% or one in five of all pregnant women, most of whom are untreated and unidentified. Regionally, this ranges from 11% in eastern Asia to up to 35% in the Caribbean. The highest numbers of colonised pregnant women in 2015 were found in India (2.5 million), China (1.9 million), Nigeria (1.1 million), the USA (0.9 million) and Indonesia (0.8 million).
Globally, at least 57,000 stillbirths and 90,000 infant deaths can be attributed to GBS infection, every year. The study found that Africa had the highest burden, with an estimated 65% of all GBS-related stillbirths and infant deaths in 2015.
The series of eleven papers in the Clinical Infectious Diseases journal, that present the research findings, was funded by a grant from the Bill & Melinda Gates Foundation. It constitutes the first comprehensive worldwide picture of GBS infection in pregnant women, also taking into account multiple GBS-related health outcomes, for women themselves as well as newborn and infant disease, stillbirth, neurodevelopmental impairment, prematurity, and neonatal encephalopathy.
Up to a third of all adults carry GBS, usually without symptoms; however, babies are more vulnerable to infection due to their immature immune systems which cannot fight off multiplying bacteria. GBS can cause serious infections such as meningitis and septicaemia which can lead to newborn and infant death. Babies that survive can develop permanent problems including hearing loss, vision loss and cerebral palsy.
This work has more than doubled previously available data, through comprehensive systematic reviews as well as use of unpublished data from collaborators worldwide, but there are still key gaps, notably for stillbirths (especially in Asia), disability (especially after GBS sepsis), and maternal GBS disease. Consequently, the authors emphasised that the results are conservative and likely to be underestimates – the total burden could be much higher.
Currently, GBS prevention focuses on provision of antibiotics to women in labour, aiming to reduce early onset infections in newborns. The series found that at least 60 countries have a policy for antibiotic use in pregnancy to prevent newborn GBS infection; however, implementation varies around the world and would not feasible for many low-income countries, where the burden is highest.
Professor Joy Lawn, the series co-lead and Professor of Maternal, Reproductive and Child Health at LSHTM, 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 44 million births take place at home, and even for hospital births the laboratory capacity for screening for GBS is limited. In addition, giving antibiotics to 21.7 million women may contribute to antimicrobial resistance – an important global health crisis.”
Even in high income settings, where provision of medicine to women in labour can be achieved more easily, use of antibiotics does not address the whole scope of the problem. As Dr Anna Seale, Series co-lead and Associate Professor at LSHTM, noted: “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.”
So, what’s next? The study investigated the potential of maternal immunisation for reducing the worldwide burden of GBS and showed, for the first time, that a maternal GBS vaccine with 80% efficacy and 90% coverage could potentially prevent 231,000 infant and maternal GBS cases, in turn reducing other outcomes such as stillbirths, death and later impairment.
Dr Keith Klugman, Director of the Pneumonia Team at the Bill & Melinda Gates Foundation, commented “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.”
However, despite GBS accounting for more than the combined neonatal deaths from tetanus, pertussis, and respiratory syncytial virus, for which maternal vaccines are already in use or advanced development, no vaccine is currently available for maternal GBS.
Johan Vekemans, co-author and Medical Officer, Initiative for Vaccine Research, World Health Organization, provides a positive vision for the future of GBS: “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 GBS vaccine development. 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.”
Read the Series executive summary here
Open access supplement here.