Vaxcyte, Inc. announced the publication of preclinical data for VAX-A1, the company’s novel Group AStreptococcus (Group A Strep) conjugate vaccine candidate, in the journal Infectious Microbes & Diseases. Group A Strep is one of the leading causes of bacterial infections worldwide, including strep throat and certain severe invasive infections such as sepsis, necrotizing fasciitis and toxic shock syndrome. Strep throat is particularly common in school-age children and a significant source of antibiotic prescriptions globally. The Group A Strep pathogen is also a leading cause of mortality in emerging countries by eliciting immune-mediated diseases such as rheumatic fever and rheumatic heart disease. The World Health Organization (WHO) has recognized the significant public health need caused by Group A Strep and has articulated a strategic goal to develop a safe and globally effective Group A Strep vaccine for prevention of acute infections, secondary immune-mediated sequelae and disease-associated mortality and to reduce reliance on antibiotics to help mitigate the growing concern of antibiotic resistance. In the study, a novel protein and polysaccharide conjugate of the Group A Strep polysaccharide was constructed for inclusion in a universal subunit vaccine against infections by the pathogen. The study demonstrated that active immunization of mice with the vaccine protected against a Group A Strep challenge in systemic infection and localized skin infection models. Moreover, the antibodies induced by the vaccine bound to a wide array of genetically distinct circulating strains of Group A Strep, without evidence of cross-reactivity to human heart or brain tissue antigens. The study referenced in the paper, “Site-Specific Conjugation of Cell Wall Polyrhamnose to Protein SpyAD Envisioning a Safe Universal Group A Streptococcal Vaccine,” was carried out in collaboration with researchers at the Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California School of Medicine and the Skaggs School of Pharmacy and Pharmaceutical Sciences at UC San Diego. Highlights of Findings from the Preclinical Study: The study examined the efficacy of a novel polysaccharide protein conjugate for a vaccine covering all serotypes of Group A Strep. The vaccine elicited antibodies that were protective in systemic and soft tissue mouse models of infection. Broad-based cross-reactivity with multiple M-protein serotypes of Group A Strep was observed in the serum of vaccinated animals. No cross-reactivity was detected with human heart or brain proteins. About Group A Streptococcus: Streptococcus pyogenes (S. pyogenes or Group A Strep) is a preeminent human pathogen causing 700 million cases of disease annually, the majority of which are pharyngitis, commonly known as strep throat. Pharyngitis is highly prevalent in school-age children and a significant source of antibiotic prescriptions, contributing to the growing problem of antibiotic resistance globally. In the United States, an estimated 17.1% of outpatient antibiotic prescriptions dispensed to children aged 3 to 9 years are for treatment of suspected Group A Strep infections. Studies indicate that antibiotic resistance to Group A Strep has significantly increased in this past decade. For example, from 2010 to 2017, the percentage of Group A Strep infections that are resistant to erythromycin has nearly tripled from 8% to 23%, resulting in the elevation of the bacteria by the U.S. Centers for Disease Control (CDC) to the antibiotic resistant category of a “concerning threat.” Group A Strep also increases the risk of severe invasive infections, such as sepsis, necrotizing fasciitis and toxic shock syndrome, and is responsible for post-infectious, immune-mediated rheumatic heart disease (RHD), a leading cause of mortality in emerging countries. Some 30 million people are currently affected by RHD, with over 300,000 deaths in 2015 and 10.5 million disability-adjusted life years lost.