Maternal Vaccine Could Prevent Group B Streptococcus

Approximately 18 percent of pregnant women are carrying Group B Streptococcus (GBS) bacteria, which is a major cause of maternal and infant death.

But, these infant deaths could be prevented with a vaccine.

These are the findings of a new research led by the London School of Hygiene and Tropical Medicine (LSHTM), which estimates that there will be at least 147,000 stillbirths and infant deaths globally.

This 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 the bacteria, totalling 21.7 million in 195 countries.

Group B Streptococcus is a type of bacteria that occurs naturally in the lower vaginal tract, and causes illness in people of all ages.

Most babies exposed to GBS will be unaffected, but one in every 200 cases can become infected.

As newborn babies’ immune systems aren’t fully developed, Strep B bacteria can quickly spread through their body, causing serious infections, such as meningitis.

Group B strep disease is the most common cause of severe infections in newborns that can be deadly, but it can be prevented, says the Centers for Disease Control and Prevention (CDC).

Dr. Anna Seale, 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," said Dr. Seale.

According to the CDC, there are two ways to prevent early-onset (infants 1 week old) group B strep disease include:

• Testing all pregnant women for group B strep bacteria late in pregnancy (ideally between 35 and 37 weeks pregnant).
• Giving antibiotics during labor to women who test positive for group B strep bacteria.

An a analysis showed 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.

This study’s decision-analytic model based on South African data compared four strategies: no intervention, maternal GBS vaccination, RFB-IAP, and vaccination plus RFB-IAP.

GBS vaccination alone was predicted to prevent 30–54% of infant GBS cases compared to no intervention.

For vaccine prices between $10 and $30, and mid-range efficacy, its cost ranged from $676 to $2,390 per disability-adjusted life-year (DALY) averted ($US 2010), compared to no intervention.

Although several vaccines to prevent GBS are in development, none is currently available.

Recently, a vaccine manufacturer (GSK) has developed and commenced clinical trials with a new CPS conjugate vaccine, based on CRM197 as the conjugate protein.  Randomized clinical trials during pregnancy are underway; some have been reported as conference abstracts and some results are available on clinicaltrials.gov (NCT01193920, NCT01446289, NCT02046148).

Another manufacturer (MinervaX) has recently commenced phase 1 clinical trials with a protein vaccine (GBS-NN), made from the N-terminal domains of the Rib and AlphaC surface proteins of GBS (NCT02459262).

Additionally, the attitude of regulators and policy makers towards vaccination during pregnancy has changed.

This is exemplified by the World Health Organization's global recommendations on flu vaccines in pregnant women and CDC recommendations for pertussis vaccine in pregnant women. 

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.

The London School of Hygiene & Tropical Medicine is a world-leading centre for research and postgraduate education in public and global health.

This first comprehensive study of the burden of GBS was funded by a grant from the Bill & Melinda Gates Foundation.