Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

The polysaccharide-encapsulated bacteria, Haemophilus influenzae type b, Neisseria meningitidis and Streptococcus pneumoniae are important causes of invasive bacterial infection in childhood, accounting for most of the cases of bacterial pneumonia and meningitis worldwide. Protein-polysaccharide conjugate vaccines have been developed over the last 20 years and have proven very effective in controlling these infections. Although studies have consistently shown that herd immunity is critical for population protection, long-term individual protection against polysaccharide-encapsulated bacteria appears to depend on persisting antibody and, perhaps to a lesser extent, immunological memory. However, some studies have reported that the concentration of serum antibody and vaccine effectiveness are not sustained after infant immunization, despite persistence of immunological memory. In this article, we detail the mechanisms of protection against invasion by encapsulated bacteria, describe the age-dependent B-cell and antibody responses to protein-polysaccharide conjugate vaccines and propose strategies to guarantee protection during periods of increased disease burden.

Original publication




Journal article


Expert Rev Vaccines

Publication Date





673 - 684


Antibodies, Bacterial, Bacterial Proteins, Bacterial Vaccines, Haemophilus Infections, Haemophilus influenzae, Humans, Immunity, Herd, Immunologic Memory, Infant, Meningococcal Infections, Neisseria meningitidis, Pneumococcal Infections, Polysaccharides, Bacterial, Streptococcus pneumoniae, Time Factors, Vaccination, Vaccines, Conjugate