29 December 2009

Meningococcal Vaccine:

 Does Our Risk for Meningococcal Disease Warrant Routine Immunization?

Meningococcal disease is devastating, both in the form of meningitis, and in the less common but more deadly infection of the blood stream, (septicemia) and septic shock. Periodic outbreaks have occurred in the US, particularly among college students and military recruits. The main concern for us as short-term volunteers is its presence in both endemic and epidemic form in the so-called meningitis belt of Sub-Saharan Africa, (See map), and in parts of Asia.

Over 500,000 cases occur each year worldwide, and over 50,000 deaths. Although easily treated with high dose penicillin or chloremphenicol, the disease has a 10-15% mortality rate and a 20% incidence of significant neurologic residual. Young children and adolescents are at the highest risk, particularly after prolonged exposure under crowded conditions, such as in schools and military camps. Interestingly, adults over the age of 50 are much less susceptible. The largest recorded epidemic occurred in the African meningitis belt in 1996, with 250,000 cases and 25,000 deaths.

Meningococcal disease is predominantly caused by 5 serogroups, which somewhat complicates the vaccine picture. Type A and type C cause most of the disease in Sub Saharan Africa and Asia. Type B causes most of the disease in the US and Europe. Two types of vaccine are currently available, the polysaccharide, which has been in use for 30 years, and the new highly preferable conjugate vaccine. The conjugate quadrivalent vaccine, MCV4, is 90-95% protective after a single dose. The duration of protection is not known, but is at least 3 years.

The major question is: Does our risk of acquiring meningococcal disease warrant routine immunization? According to the CDC current recommendations:

• Vaccination is recommended for persons who travel to epidemic areas either during outbreaks or if contact with the local population will be prolonged

• Vaccination is advised for persons traveling to the meningitis belt of Africa during the dry season (December through June).

• Quadrivalent conjugate vaccine (MCV4) is currently indicated for persons 2-55 years of age.

• For further details on dosage and indications for administration, refer to cdc.gov/travel.

Ref: Wilder-Smith, A; Meningococcal Vaccines: A Neglected Topic in Travel Medicine? Expert Reviews of Vaccines. 2009; 8:1343-50.
Roger Boe MD

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