21.7 million pregnant women carry the bacteria according to this first global study of Group B Strep - most of them are currently unidentified and untreated. This study shows for the first time that a maternal vaccine may prevent 231,000 infant and maternal GBS cases.

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, 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% of the world’s population, Africa had the highest burden, with 54% of estimated cases and 65% 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% of pregnant women worldwide carrying (colonised with) the bacteria, ranging from 11% in eastern Asia to 35% 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% effective and reached 90% 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 S