Pneumococcal polysaccharide serotype 16F conjugated to CRM197

Table of contents

• What is pneumococcal polysaccharide serotype 16F?
• How does pneumococcal polysaccharide serotype 16F work?
• Which conditions is it used or studied for?
• How is pneumococcal polysaccharide serotype 16F given?
• What do the clinical trials show?
• Who can take part in these trials?

What is pneumococcal polysaccharide serotype 16F?

Pneumococcal polysaccharide serotype 16F conjugated to CRM197 is a component of CAPVAXIVE, a pneumococcal polysaccharide conjugate vaccine (21-valent) authorised as a medicine in the European Union.^[1] The substance is a polysaccharide from the bacterium Streptococcus pneumoniae serotype 16F, chemically linked (conjugated) to a carrier protein called CRM197. The product is supplied by Merck Sharp & Dohme B.V. and holds the EU marketing authorisation number EU/1/25/1913/001.^[1] The registry name lists the substance as part of a fixed combination with 20 other pneumococcal polysaccharide serotypes in one product record.^[1]

How does pneumococcal polysaccharide serotype 16F work?

Pneumococcal conjugate vaccines work by presenting bacterial polysaccharides linked to a carrier protein. This linkage helps the immune system recognise and respond to the polysaccharide more effectively than it would to the polysaccharide alone. The immune response is measured in the trials as the level of serotype-specific immunoglobulin G (IgG) antibodies in the blood, including a seroconversion defined as a two-fold or four-fold increase in vaccine-type IgG after vaccination.^[2] The trials assess whether the vaccine produces an immune protective response, defined as an ELISA IgG level of at least 1.3 micrograms per millilitre in at least 10 of 13 tested vaccine serotypes.^[2]

Which conditions is it used or studied for?

• Asplenia — patients without a spleen, a condition that increases the risk of serious pneumococcal infection. One trial studies vaccination before or after spleen removal.^[1]
• Medium or high risk for pneumococcal invasive infection — adults at increased risk of invasive pneumococcal disease, including during an acute febrile illness.^[2]

How is pneumococcal polysaccharide serotype 16F given?

The substance is given as a solution for injection in a pre-filled syringe, administered by intramuscular injection. The dose used in the trials is 0.5 millilitres.^[1][2] CAPVAXIVE is the marketed product containing this substance along with 20 other pneumococcal serotypes.^[1]

What do the clinical trials show?

Two Phase 3 interventional trials are authorised and listed in the registries, together involving 1,230 participants. Both trials compare CAPVAXIVE (PCV21) with Prevenar 20 (PCV20), a 20-valent pneumococcal conjugate vaccine used as the comparison arm.^[1][2]

The first trial (70 participants) measures the mean fold change of serotype-specific IgG concentrations against pneumococcal serotypes common to PCV20 and PCV21, two to three weeks after a booster vaccination with PCV21 given at least 12 months after primary vaccination with PCV20 in asplenic patients.^[1]

The second trial (1,160 participants) measures the proportion of immune "good responders" to PCV20 or PCV21 one month after vaccination. A good responder is defined as having a seroconversion for at least 10 of 13 tested vaccine serotypes and an immune protective response, or a four-fold increase in vaccine-type IgG with an immune protective response in at least 10 of 13 tested serotypes.^[2] This trial aims to show that vaccination during an acute febrile illness produces an immune response that is non-inferior to vaccination given 15 to 58 days after the illness has resolved.^[2]

Who can take part in these trials?

The trials enrol adults with specific risk profiles. The asplenia trial includes patients who have had their spleen removed or are scheduled for splenectomy, vaccinated either before or after the procedure.^[1] The larger trial enrols unvaccinated patients at medium or high risk for pneumococcal infections, including those with an acute febrile illness at the time of vaccination.^[2] Both trials are authorised, meaning they have received regulatory approval to proceed, though recruitment status is not detailed in the registry records provided.