Long-term protection after immunization with protein–polysaccharide conjugate vaccines in infancy

Abstract

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.

Keywords::

• antibody
• B cells
• encapsulated bacteria
• long-term immunity
• protein–polysaccharide conjugate vaccines

Financial & competing interests disclosure

Geraldine Blanchard-Rohner was funded by the Swiss National Science Foundation. This work was supported by the Oxford Partnership Comprehensive Biomedical Research Centre Programme with funding from the Department of Health’s NIHR Biomedical Research Centres funding scheme. Andrew J Pollard is a Jenner Institute Investigator and acts as chief and principal investigator for clinical trials conducted on behalf of the University of Oxford, sponsored by vaccine manufacturers (Novartis Vaccines, GlaxoSmithKline, Sanofi-Pasteur, Sanofi-Pasteur MSD and Wyeth Vaccines), but does not receive any personal payment from them. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.