CASE-CONTROL STUDY
PCV13 effectiveness
A US matched case-control study evaluated protection against invasive pneumococcal disease among vaccinated children.
READ STUDY ↗
VACCINE PROFILE / CAPSULAR IMMUNOLOGY
Pneumococcal
Vaccines.
Explore capsular serotype diversity, conjugate vaccine design, and the immune mechanisms that help protect against invasive pneumococcal disease, including pneumococcal meningitis.
EXPLORE VACCINE PLATFORMS ↗
FIG 01 / ENCAPSULATED PNEUMOCOCCUS
Original illustration of capsular organization
01 / CAPSULAR BIOLOGY
The capsule
defines the target.
Streptococcus pneumoniae is an encapsulated Gram-positive bacterium capable of causing pneumonia, bloodstream infection, and meningitis.
Its polysaccharide capsule is a major virulence factor and an important vaccine antigen. Pneumococci possess many distinct capsular serotypes, but individual vaccine formulations target selected subsets.
Key principle:
Vaccine-valency numbers describe
how many pneumococcal serotypes
a formulation includes, not a
percentage of total protection.
02 / VACCINE TECHNOLOGY
Conjugate and polysaccharide
vaccine strategies.
Two major vaccine platforms target pneumococcal capsular polysaccharides, but they differ in immune-response characteristics.
PLATFORM A / PCV
Pneumococcal conjugate vaccines
PCVs attach capsular polysaccharides to carrier proteins, promoting T-cell-dependent responses and immunological memory.
EXAMPLES / PCV15 · PCV20 · PCV21
PLATFORM B / PPSV
Pneumococcal polysaccharide vaccines
PPSV formulations contain purified capsular polysaccharide antigens. Their immune-response characteristics differ from protein-conjugated vaccines.
EXAMPLE / PPSV23
03 / VACCINE EPIDEMIOLOGY
Protection changes
the serotype landscape.
Pneumococcal vaccination can reduce disease caused by vaccine serotypes. Surveillance also tracks the circulation of serotypes not included in a given formulation.
01 / DIRECT PROTECTION
Vaccine-serotype disease
Vaccination can reduce invasive disease caused by the serotypes included in a vaccine.
02 / INDIRECT EFFECTS
Population protection
Reduced carriage of some vaccine serotypes can contribute to indirect protection.
03 / CONTINUED SURVEILLANCE
Serotype replacement
Non-vaccine serotypes may occupy ecological niches as vaccine-type carriage declines.
04 / PEER-REVIEWED EVIDENCE
Evidence from clinical
and population studies.
POPULATION STUDY
Pneumococcal meningitis impact
A Finnish population study investigated the long-term effects of infant PCV10 vaccination on pneumococcal meningitis.
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EPIDEMIOLOGICAL STUDY
Serotype replacement
Research from England and Wales evaluated indirect protection and changes in non-vaccine serotype disease after PCV7.
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05 / SCIENTIFIC ANSWERS
Pneumococcal
vaccine essentials.
Do pneumococcal vaccines prevent meningitis?
They help prevent invasive pneumococcal disease caused by covered serotypes, including pneumococcal meningitis.
What is the difference between PCV and PPSV?
PCVs link capsular polysaccharides to carrier proteins, promoting T-cell-dependent immune responses. PPSV vaccines use purified polysaccharide antigens.
What is pneumococcal serotype replacement?
It describes an increase in the relative or absolute circulation of some non-vaccine serotypes after vaccine-type carriage declines.
06 / REFERENCES
Scientific literature.
- WHO — Pneumococcal Conjugate Vaccine Position Paper (2025).
- CDC — Pneumococcal Vaccination.
- PCV13 effectiveness in US children.
- Long-term effects on pneumococcal meningitis in Finland.
- Herd immunity and serotype replacement in England and Wales.
Educational scientific information. Vaccine indications and schedules depend on current recommendations, age, risk factors, and vaccine history.
NEXT / VACCINE ATLAS 09
Hib Vaccines
Explore Haemophilus influenzae type b conjugate vaccine biology.