Meningococcal polysaccharide vaccination of military recruits in Israel: preliminary assessment of vaccine effect

Preventive effect of meningococcal vaccination in Israeli military recruits

BACKGROUND

Meningococcal disease remains a major concern in populations living under crowded conditions. Following the 1995 report of several cases of meningococcal disease in Israeli soldiers, the Department of Epidemiology of the Army Health Branch, Israel Defense Forces (IDF) adopted an immunization policy for all recruits. The aim of the study was to summarize the IDF experience to date.

METHODS

The study population included all compulsory and permanent personnel of both sexes serving in the IDF from 1983 to 2007. Ages ranged from 18 to 55 years, although the majority of subjects was younger than 22 years. Meningococcal disease was defined as the isolation of Neisseria meningitidis from blood or cerebrospinal fluid.

RESULTS

The person-time incidence rate of vaccine-preventable meningococcal disease dropped from 1.31 cases per 100,000 person-years in 1983-1994, the period preceding the start of immunization, to 0 in 1995-2007 (P < .001).

CONCLUSION

The meningococcal immunization policy of the IDF led to a dramatic drop in the incidence of vaccine-preventable meningococcal disease.

Scientific challenges for the quality control and production of group C meningococcal conjugate vaccines

Recommendations (formerly known as requirements) for meningococcal polysaccharide vaccines were adopted by the World Health Organisation (WHO) Expert Committee on Biological Standardisation in 1976 and amended in 1978 and 1981. In clinical studies, these vaccines have been shown to have efficacy of at least 90% and have proved to be highly effective in vaccination programmes. Nevertheless, their inability to elicit protective responses in young infants or to induce good immunological memory has prevented their implementation in national infant immunisation schedules. Following the successful introduction of the Haemophilus influenzae type b conjugate (Hib) vaccines, considerable progress has been made in the development of similar conjugate vaccines based on meningococcal group C capsular polysaccharide. Controlled clinical trials have demonstrated that they induce protective levels of antibodies to group C polysaccharide in all age groups and, as T-cell dependent antigens, induce immunological memory and affinity maturation of anti-capsular antibodies. Such vaccines have been shown to offer protective immunity following the introduction of group C conjugates in the UK. The World Health Organisation has produced recommendations for the production and control of these new vaccines.