[This article has been written by Percy Efrain Pantoja, Medical Research Fellow, and Elena Marbán, Predoctoral Fellow]
Worldwide, GBS is a major cause of death in the first months of life
July is the international Group B Streptococcus (GBS) Awareness Month. This initiative arose from the awareness, promotion and prevention campaigns led by associations of parents whose babies were affected by the bacterium in USA and UK. The bacterium was first described in 1970, but it was the death of three babies in 1989 that prompted a call for public attention together with efforts to develop preventive strategies.
Most babies that enter in contact with the bacterium do not get sick, but those that do can suffer from severe or even lethal consequences
Worldwide, GBS is a major cause of death in the first months of life; it produces pneumonia, sepsis and meningitis. Most babies that enter in contact with the bacterium do not get sick, but those that do can suffer from severe or even lethal consequences. Before birth, it can lead to spontaneous late abortions and pre-term births; after birth, it can present as early disease (up to the first week after birth) or late disease (from one week to several months later).
To date, there are no available tools to prevent perinatal infection by GBS, despite it causing more neonatal deaths than whooping cough, tetanus and respiratory syncytial virus together.
GBS transmission can occur before, during and up to six weeks after birth
But we are talking of a preventable problem of public health, with a challenging side and another one in development. On one hand, GBS transmission can occur before, during and up to six weeks after birth. One third of the world population is colonised by GBS in the gut and/or in the lower genital tract, without having any symptoms. One out of five women carries GBS, which is associated with higher risk of urogenital infections, chorioamnionitis and endometriosis.
The screening test has not been implemented in any African country, where prevention would have the most impact
Many high-income countries, including Spain, perform universal GBS screening during pregnancy. The test consists in a vaginal discharge culture to detect the bacterium and if positive, administer antibiotics during delivery to avoid contagion. However, this screening test has not been implemented in any African country, where prevention would have the most impact; the incidence of neonatal GBS disease in African countries can be 10 times higher than in Europe. Interrupting GBS transmission and providing timely treatment in low-resource countries represents the first challenge, since this requires the implementation of systematic screening which in turn needs more health centres, laboratories, health care staff and specialized technicians.
Countries that have implemented universal screening for GBS colonization during pregnancy (Image byGBS International)
Although there is still no licensed vaccine against GBS, there are several products in development
Although there is still no licensed vaccine against GBS, there are several products in development. Of the 10 serotypes, more than 90% of early disease cases are caused by serotypes Ia, Ib, II, III y V, while late disease is mostly caused by serotype III. Currently, several GBS vaccine candidates are in Phase 1 or 2 clinical trials: trivalent or pentavalent vaccines (with the most frequent serotypes) or conjugated vaccines that induce immunoglobulins type G which can pass from mother to child via the placenta. These vaccines are being evaluated for their safety, tolerance and immunogenicity. Phase 3 studies are limited by the low incidence of GBS in neonates and pregnant women, particularly in richer countries. The universal licensing and implementation of an effective vaccine is necessary and the strategy will probably be similar to that used for the conjugated pneumococcal vaccine based on assessing individual immune responses with standardised immune assays.
Despite progress made over the last years in diagnosing and treating GBS, invasive infection by the bacterium remains a major public health problem worldwide. Vaccinating pregnant women is the most promising tool in the medium-term to avoid pathogen transmission to the baby.
Vaccinating pregnant women is the most promising tool in the medium-term to avoid pathogen transmission to the baby
Therefore, global efforts are required to establish collaborations and bring together research teams on global health, with the ultimate goal of contributing to universal and effective screening and developing a vaccine that ensures adequate protection for mothers and babies and, above all, reaches the populations that most need it.