Pneumococcal polysaccharide serotype 23B conjugated to CRM197

Table of contents

• What is pneumococcal polysaccharide serotype 23B?
• How does pneumococcal polysaccharide serotype 23B work?
• Which conditions is it used or studied for?
• How is pneumococcal polysaccharide serotype 23B given?
• What do the clinical trials show?
• What side effects are known?

What is pneumococcal polysaccharide serotype 23B?

Pneumococcal polysaccharide serotype 23B conjugated to CRM197 is one of 21 pneumococcal serotype components in CAPVAXIVE, a pneumococcal polysaccharide conjugate vaccine (21-valent). The substance is a protein-based polysaccharide conjugate, meaning the pneumococcal polysaccharide is chemically linked to a carrier protein called CRM197.^[1] In the registry, the full substance name lists 21 individual pneumococcal polysaccharide serotypes, each conjugated to CRM197, including serotype 23B.^[1]

CAPVAXIVE is authorised as a medicine in the European Union, with authorisation record EU/1/25/1913/001.^[1] The authorisation holder is Merck Sharp & Dohme B.V.^[1] The product is a solution for injection in a pre-filled syringe.^[1]

How does pneumococcal polysaccharide serotype 23B work?

Pneumococcal conjugate vaccines work by presenting pneumococcal polysaccharides linked to a carrier protein to the immune system. This conjugation helps the immune system recognise and respond to the polysaccharide, producing antibodies against the pneumococcal serotypes included in the vaccine. The immune response is intended to protect against infections caused by Streptococcus pneumoniae, the bacterium responsible for pneumococcal disease.

Pneumococcal serotypes differ in their potential for colonisation, invasiveness and virulence. Serotypes with low invasive potential, such as types 3, 6A, 6B, 8, 19F and 23F, behave as opportunistic pathogens in at-risk individuals, whereas serotypes with high invasive potential, such as types 1 and 7F, can act as primary pathogens in previously healthy individuals.^[4]

Which conditions is it used or studied for?

• Asplenia — a condition in which a person has no spleen or the spleen does not function. People without a spleen are at higher risk for severe pneumococcal infections, and one trial studies vaccine response in these patients.^[1]
• Medium or high risk for pneumococcal invasive infection — adults with conditions that increase their risk for serious pneumococcal disease. One trial studies vaccination during an acute febrile illness in this population.^[2]

How is pneumococcal polysaccharide serotype 23B given?

CAPVAXIVE is given as a solution for injection in a pre-filled syringe, administered by intramuscular injection. Each dose is 0.5 ml.^[1] The route of administration recorded in the registry is intramuscular injection.^[1]

What do the clinical trials show?

Two Phase 3 trials are registered for CAPVAXIVE, which contains pneumococcal polysaccharide serotype 23B conjugated to CRM197. Both trials are authorised, meaning they have received regulatory approval to proceed. The trials involve a total of 1,230 participants.

The first trial (2024-515363-63-00) includes 70 participants with asplenia and measures the mean fold change of pneumococcal serotype-specific IgG antibodies against common serotypes present in both PCV20 and PCV21 vaccines, 2–3 weeks after booster vaccination with PCV21.^[1] The second trial (NCT06822907) includes 1,160 participants at medium or high risk for pneumococcal invasive infection and measures the proportion of immune "good responders" to PCV-20 or PCV-21 at one month after vaccination.^[2]

Both trials compare CAPVAXIVE (PCV21) with Prevenar 20 (PCV20), a 20-valent pneumococcal conjugate vaccine. The primary outcomes measure immune responses, including seroconversion and protective antibody levels, rather than clinical disease outcomes.

What side effects are known?

The supplementary sources provided do not contain specific side effect data for CAPVAXIVE or pneumococcal polysaccharide serotype 23B conjugated to CRM197. The sources discuss pneumococcal vaccination patterns and serotype epidemiology but do not report adverse events for this specific 21-valent conjugate vaccine.^[3][5]