Where do we stand with vaccination for haemolytic streptococci?

Haemolytic streptococci impose a considerable healthcare burden. Group B streptococci are a significant cause of neonatal mortality, while group A streptococci remain a leading cause of infection worldwide. Dr Kostas Karampatsas (St George’s University of London, UK) reviewed the current evidence on vaccine candidates targeting both group B and group A streptococci [1]. 

Two group B streptococcus vaccines are in advanced development: the hexavalent polysaccharide conjugate vaccine GBS6 and the protein subunit vaccine GBS-NN/NN2. In a phase 2 trial, a single dose of GBS6 administered to pregnant women induced anti-CPS IgG responses in both mothers and newborns across all 6 serotypes included in the vaccine [2]. Separately, GBS-NN/NN2 was evaluated in a phase 1 trial involving healthy, non-pregnant women, eliciting both IgA and IgG antibody responses against all 4 Alp-N-terminal domains included in the vaccine [3]. Both these vaccines have phase 3 trials planned [1]. However, the path to licensure is complicated by the lack of assay standardisation for determining immunogenicity. This issue is being addressed through the Group B Streptococcus Assay STandardisatiON (GASTON) consortium collaboration [4]. 

Multiple group A streptococcus vaccine candidates are also under evaluation, following 2 main strategies. M protein-based vaccines are the most advanced, with phase 1 trial results showing immunogenicity and acceptable safety. In contrast, non-M protein approaches remain in preclinical development [5]. To support vaccine development, a human challenge model for S. pyogenes infection has recently been established, helping to define antibody correlates of protection for upcoming clinical trials [6]. 

“In conclusion, vaccines against group B streptococcus are within reach,” said Dr Karampatsas, “with 2 candidates in late-stage development and trials either completed or nearing completion. The road for group A streptococcus is more complex and less straightforward, but international collaboration and assay standardisation are helping to move the field forward.” 

1. Karampatsas K, et al. Are we ready for vaccinations against haemolytic streptococci? 6th ESCMID Vaccines, 10–13 September 2025, Lisbon, Portugal. 


2. Madhi SA, et al. N Engl J Med. 2023;389(3):215-227. 


3. Gonzalez-Miro M, et al. iScience. 2023;26(3):106261. 


4. Le Doare K, et al. Hum Vaccin Immunother. 2024;20(1):2330138.  


5. Walkinshaw DR, et al. NPJ Vaccines. 2023;8(1):16.  


6. Osowicki J, et al. Nat Commun. 2024;15:10506.  

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Posted on 21 October 2025