PCVs in individuals at increased risk of pneumococcal disease: a literature review

Abstract

The use of pneumococcal conjugate vaccine (PCV) in childhood pneumococcal immunization programs successfully reduced the incidence of pneumococcal disease in children. Nonetheless, there remains a high burden of pneumococcal disease in adults, especially the elderly, and children/adults with chronic medical conditions. Two pneumococcal vaccines are currently available for adults at risk of pneumococcal disease: the 23-valent pneumococcal polysaccharide vaccine (PPV23) and the more recently licensed PCV13. As it is not possible to determine vaccine efficacy in all populations at risk of pneumococcal disease, immunogenicity studies, measuring pneumococcal-specific antibody concentrations and/or the opsonophagocytic activity of serum can provide valuable comparative data for PPV and PCV immunization. This article provides consolidated data on the immunogenicity of PCVs (largely PCV7, and a few studies with PCV9 or PCV13) based on a review of immunogenicity/safety studies in populations (mainly pediatric) at increased risk of pneumococcal disease.

Keywords:

• ELISA
• immunocompromised
• immunogenicity
• opsonophagocytic activity
• PCV
• risk group
• vaccination schedule

Acknowledgements

The authors take full responsibility for the content of this article and thank Neostar Communications Limited, Oxford, UK (funded by Pfizer, France) for their assistance in preparing the manuscript. The authors also wish to thank their Pfizer, USA colleagues, Rosalind Hollingsworth and Raul Isturiz, for their review of the manuscript.

Financial and competing interests disclosure

N Dartois and MA Fletcher are employees of Pfizer, France. E Bonnet was an employee of Pfizer, France. P Balmer is an employee of Pfizer, USA. The authors received writing assistance from Neostar Communications, and this was funded by Pfizer, France. 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.

Key issues

• The majority of safety and immunogenicity trials of PCV7 in children and adults at increased risk of pneumococcal disease were single arm (non-comparative)

• The methodology used to assess serotype-specific IgG and S. pneumoniae varied across trials, as did the immunogenic response criteria; there is currently no standardized protocol for OPA and no protective thresholds have been established.

• Immunogenicity of PCV7, as assessed by pneumococcal-specific antibody concentrations and/or OPA activity, has been demonstrated in immunocompetent, immunocompromised and asplenic children and adults at risk of pneumococcal disease.

• In HIV-infected adults, PCV7 primary vaccination resulted in significantly greater antibody concentrations and/or functional activity than PPV23, and subsequent PPV23 vaccination did not appear to enhance the PCV7 immune response.

• PCV7 or PCV9 vaccination was also immunogenic in children with HIV, although functional responses tended to be lower in HIV-infected children than in HIV-uninfected children.

• The benefits of early PCV7 vaccination were demonstrated in children and adults undergoing stem cell transplantation (either prior to or early after transplantation).

• PCV7 immunogenicity was demonstrated in adults and children undergoing solid organ transplants with some variability being reported according to the organ involved (e.g., heart or lung recipients appear to have the lowest responses).

• The immunogenicity of PPV23 following PCV7 primary vaccination varied within asplenic individuals; sequential PCV7 and PPV23 vaccination was immunogenic in infants with sickle cell disease, whereas PPV23 did not further enhance immune responses in adults with asplenia following primary PCV7 vaccination.

• There is also evidence from comparative trials that PCV7 may be more immunogenic than PPV23 in children with asthma or a cochlear implant and adults with chronic lung disease.

Notes