Pneumococcal polysaccharide serotype 35B conjugated to CRM197

What is on this page?

• What is pneumococcal polysaccharide serotype 35B?
• How does pneumococcal polysaccharide serotype 35B work?
• Which conditions is it used or studied for?
• How is pneumococcal polysaccharide serotype 35B given?
• What do the clinical trials show?
• What side effects are known?

What is pneumococcal polysaccharide serotype 35B?

Pneumococcal polysaccharide serotype 35B conjugated to CRM197 is a component of CAPVAXIVE, a pneumococcal polysaccharide conjugate vaccine (21-valent) authorised as a medicine in the European Union under authorisation record EU/1/25/1913/001.^[1] The substance is a purified polysaccharide from the surface of the bacterium Streptococcus pneumoniae, chemically linked (conjugated) to a carrier protein called CRM197, which is a non-toxic mutant of diphtheria toxin.^[3] CAPVAXIVE is supplied by Merck Sharp & Dohme B.V. and is given as a solution for injection in a pre-filled syringe.^[1] The registry lists the substance as part of a fixed combination product, meaning it is present together with polysaccharides from 20 other pneumococcal serotypes.^[1]

How does pneumococcal polysaccharide serotype 35B work?

Pneumococcal polysaccharide serotype 35B is a conjugate vaccine component. The polysaccharide from the bacterial capsule is linked to the CRM197 carrier protein, which is a non-toxic mutant of diphtheria toxin expressed recombinantly in Pseudomonas fluorescens.^[3] This conjugation helps the immune system recognise the polysaccharide and produce specific antibodies against serotype 35B. The resulting immune memory is intended to protect against invasive pneumococcal disease caused by this serotype. The clinical programme measures the antibody response as an indicator of this protection.^[1][2]

Which conditions is it used or studied for?

• Asplenia — a condition in which the spleen has been removed or does not function. People without a spleen have a higher risk of serious pneumococcal infections, and the trial studies vaccination before or after spleen removal.^[1]
• Medium or high risk for pneumococcal invasive infection — adults with underlying conditions that make them more vulnerable to pneumococcal disease. The trial studies vaccination during an acute febrile illness compared with vaccination after recovery.^[2]

How is pneumococcal polysaccharide serotype 35B given?

The substance is given as a solution for injection by intramuscular injection.^[1] The authorised product CAPVAXIVE is presented as a 0.5 mL pre-filled syringe containing the 21-valent pneumococcal polysaccharide conjugate vaccine.^[1] In the registered trials, a single 0.5 mL dose is administered intramuscularly.^[1][2]

What do the clinical trials show?

Two phase 3 interventional trials are registered for CAPVAXIVE, the vaccine containing pneumococcal polysaccharide serotype 35B. Both trials have the status Authorised, meaning they are approved to proceed. The first trial (2024-515363-63-00) enrols 70 asplenic patients and compares CAPVAXIVE with Prevenar 20. The second trial (NCT06822907) enrols 1,160 adults at medium or high risk for pneumococcal invasive infection and also compares CAPVAXIVE with Prevenar 20.^[1][2]

What are the trials measuring?

The asplenia trial measures the mean fold change of pneumococcal serotype-specific IgG antibodies against serotypes common to both vaccines, 2–3 weeks after a booster vaccination with CAPVAXIVE given at least 12 months after primary vaccination with Prevenar 20.^[1] The febrile illness trial measures the proportion of immune "good responders" one month after vaccination. A good responder is defined as having a seroconversion (a two-fold or four-fold increase in vaccine-type IgG) for at least 10 of the 13 serotypes tested, together with an immune protective response defined as ELISA IgG at or above 1.3 μg/mL in at least 10 of the 13 serotypes.^[2]

Who can take part in these trials?

The asplenia trial enrols patients without a spleen, vaccinated either before or after spleen removal.^[1] The febrile illness trial enrols unvaccinated adults at medium or high risk for pneumococcal infections who are vaccinated either during an acute febrile illness or 15–58 days after the illness has resolved.^[2]

What side effects are known?

No side effect information specific to pneumococcal polysaccharide serotype 35B is provided in the sources for this page. The registered trials measure safety as part of their design, but detailed safety results are not reported in the registry records.^[1][2]