An evaluation of the immunogenicity and safety of a new trivalent meningococcal polysaccharide vaccine

Serogroup A meningococcal conjugate vaccines in Africa

Serogroup A meningococcal epidemics have been a recurrent public health problem, especially in resource-poor countries of Africa. Recently, the administration in mass vaccination campaigns of a single dose of the monovalent meningococcal conjugate vaccine, MenAfriVac, to the 1-29 year-old population of sub-Saharan Africa has prevented epidemics of meningitis caused by serogroup A Neisseria meningitidis. This strategy has also been shown to provide herd protection of the non-vaccinated population. Development of meningococcal conjugate vaccines covering other serogroups and enhanced use of the pneumococcal and Haemophilus influenzae type b conjugate vaccines must be pursued to fully control bacterial meningitis in sub-Saharan Africa.

Safety of a trivalent meningococcal ACW135 vaccine among young children in Ethiopia

A phase II open and parallel reactogenicity, immunogenicity and safety trivalent meningitis vaccine (Mencevax) trial was conducted on 413 volunteer 2-29-year-old rural residents in Ethiopia in November/December 2005. Adverse events (AE) were monitored at 1h, 1, 2, 3, 7 and 28 days after vaccination. No serious AE occurred except for burn injury (one) and severe malaria (one) after day 28. Irritability (45/411), loss of appetite (27/411), pain at injection site (26/412), dizziness (18/409), crying (14/411), insomnia, headache and diarrhoea (13/411) were the most frequent AEs. Overall, the vaccine is safe in the age groups studied.

A new approach to the definition of seroconversion following vaccination in a population with high background antibody concentrations

Licensure of meningitis vaccines is increasingly being made on the basis of safety and immunogenicity. For meningococcal vaccines, a measure of immunogenicity is seroconversion, usually defined as a four-fold increase in rSBA titre. However, this definition is likely to underestimate seroconversion in settings with high background immunity. Using data from a study of the immunogenicity of meningococcal polysaccharide vaccines undertaken in Ghana, a logistic regression model to estimate the probability of seroconversion as a function of pre-vaccination titre has been developed. The seroconversion rate (91%) based on a variable-fold increase in rSBA titre derived from the model was a more plausible estimate of immunogenicity than the seroconversion rate (32%) based on the fixed four-fold increase in rSBA.

Preparedness for infectious threats: public-private partnership to develop an affordable vaccine for an emergent threat: the trivalent Neisseria meningitidis ACW135 polysaccharide vaccine

With the emergence of epidemic Neisseria meningitidis W135 meningitis in Burkina Faso during early 2002, the public health community was faced with the challenge of providing access to an appropriate and affordable vaccine in time for the upcoming 2003 epidemic season. Recognizing the implications of the emergent threat, the World Health Organization developed a strategy, established a public-private partnership to provide the needed vaccine, and then ensured that a stockpile was available for future use. The trivalent N meningitidis ACW135 polysaccharide vaccine that resulted is now one of the primary tools for epidemic response in African meningitis belt countries. It will remain so for the foreseeable future and until appropriate and affordable conjugate vaccines become part of national immunization programs in the region.