Group B Streptococcus (GBS) is a common bacterium found in many healthy individuals. It often resides in the intestines or lower genital tract without causing symptoms. While generally harmless in healthy adults, GBS can pose serious risks, particularly for newborns. A vaccine is being developed to prevent GBS infections.
Understanding Group B Strep and Its Impact
GBS is carried by 10% to 30% of pregnant individuals, often without symptoms, residing in the intestines, urinary, or genital tracts. While usually benign for adults, GBS can pass to a baby during vaginal delivery, leading to severe illness in newborns.
Infection in newborns can manifest as either early-onset GBS disease, typically appearing within the first week of life, often within 24 hours of birth, or late-onset GBS disease, which usually develops between 7 days and 3 months after birth. Early-onset GBS can lead to serious conditions such as sepsis (a bloodstream infection), pneumonia (a lung infection), or meningitis (an infection of the fluid and lining around the brain). Late-onset GBS can also cause sepsis or meningitis, and while less frequently fatal than early-onset cases, it still presents significant risks.
Newborns with GBS infection may exhibit symptoms like fever, difficulty breathing, poor feeding, unusual drowsiness, or seizures. Even with treatment, about 1 in 20 babies (5%) with GBS disease may die, with preterm babies facing a higher risk. Approximately 1 in 4 babies (25%) who develop meningitis due to GBS may experience long-term neurological problems, including cerebral palsy.
How a GBS Vaccine Protects Newborns
A Group B Strep vaccine for pregnant individuals works through maternal immunization. This involves vaccinating the pregnant individual to stimulate their immune system to produce specific antibodies against GBS. These antibodies then transfer to the developing fetus through the placenta.
The transfer of these protective antibodies provides the newborn with passive immunity before their own immune system is fully developed. This passive immunity is important because GBS infections often occur very early in a newborn’s life, before they can mount an effective immune response to a vaccine given directly to them. The goal of this maternal vaccination strategy is to protect the baby from acquiring a GBS infection, particularly during birth and in the vulnerable first few months of life, reducing the risk of both early-onset and late-onset GBS disease in infants.
Current Progress and Availability of the Vaccine
The development of a GBS vaccine has been ongoing for decades, with several candidates in various stages of clinical trials. These vaccines are not yet widely available for routine use. Bringing a vaccine to market involves extensive testing for safety and effectiveness, followed by regulatory approval.
One prominent vaccine candidate, GBS6 by Pfizer, is a hexavalent glycoconjugate vaccine designed to protect against the six most common GBS serotypes, accounting for approximately 98% of GBS disease globally. This candidate has received “Breakthrough Therapy Designation” from the U.S. Food and Drug Administration (FDA) and “PRIME designation” from the European Medicines Agency, designations that expedite development and review. Pfizer’s GBS6 is currently in Phase 2 and Phase 3 clinical trials, evaluating its safety and ability to generate an immune response in pregnant individuals in countries including South Africa, the UK, and the US.
Another company, MinervaX, is also developing a GBS vaccine based on surface proteins of the bacteria, which is in mid-stage development. While a specific timeline for widespread availability is not yet definitive, these developments suggest a GBS vaccine could become available in the coming years, with the World Health Organization aiming for at least one affordable vaccine to be licensed by 2026.
The Importance of GBS Vaccination
A GBS vaccine can reduce the incidence of severe GBS disease in newborns. Globally, GBS was estimated to cause 319,000 cases of invasive neonatal disease and 90,000 deaths annually in 2015. A maternal GBS vaccination program could avert an estimated 127,000 early-onset and 87,300 late-onset infant cases globally, preventing 31,100 infant deaths and 17,900 cases of moderate and severe neurodevelopmental impairment.
The vaccine can also reduce reliance on intrapartum antibiotic prophylaxis (IAP), currently the main strategy for preventing early-onset GBS disease. While IAP is effective against early-onset disease, it does not prevent late-onset GBS disease or GBS-related complications during pregnancy, such as stillbirths and preterm births. A vaccine could also prevent an estimated 23,000 GBS stillbirths and 185,000 preterm births if it proves effective against GBS-associated prematurity. The development of a GBS vaccine prioritizes safety, as it is administered to pregnant individuals and aims to protect both the mother and the newborn.