Traveller vaccination meningococcal disease

Template:Traveller vaccination meningococcal disease Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Seyedmahdi Pahlavani, M.D. [2]

Disease cause

Neisseria meningitidis bacteria, in most cases serogroups A, B and C, Y and X. Serogroup W-135 is an increasing cause of concern.

Transmission

Transmission occurs by direct person-to-person contact and through respiratory droplets from patients or asymptomatic meningococcal carriers. Human beings are the only reservoir.

Nature of the disease

As a rule, endemic disease occurs primarily in children and adolescents, with highest attack rates in infants aged 3–12 months. Meningococcal meningitis has a sudden onset of intense headache, fever, nausea, vomiting, photophobia and stiff neck, plus various neurological signs.
Permanent neurological sequelae are common and the disease is fatal in 5% to 10% of cases. Meningococcal septicaemia is characterized by circulatory collapse, haemorrhagic skin rash and high fatality rate.

Geographical distribution

• Sporadic cases are found worldwide. In temperate zones, most cases occur in the winter months. Localized outbreaks occur in enclosed crowded spaces (e.g. dormitories and military barracks).
• In the meningitis belt of sub-Saharan Africa, large outbreaks take place during the dry season (November to June).

Recent meningococcal outbreaks due to serogroup Y (United States of America), serogroup W-135 (Saudi Arabia and sub-Saharan Africa), and serogroup X (Burkina Faso and Niger), suggest that these serogroups may be gaining in importance.

Risk for travellers

The risk of meningococcal disease in travellers is generally low.

• Those travelling to industrialized countries may be exposed to sporadic cases, mostly of A, B or C. Outbreaks of meningococcal C disease occur in schools, colleges, military barracks and other places where large numbers of adolescents and young adults congregate.
• Travellers to the sub-Saharan meningitis belt may be exposed to outbreaks, most commonly of serogroup A and serogroup W-135 disease, with comparatively very high incidence rates during the dry season.
• Long-term travellers living in close contact with the indigenous population and pilgrims visiting Mecca for the hajj or umrah are at particular risk.

Vaccine

Polysaccharide vaccines

• Internationally marketed meningococcal polysaccharide vaccines are bivalent (A and C), trivalent (A, C and W-135) or tetravalent (A, C, Y and W-135).
• Following one single dose, in most cases subcutaneous, these vaccines provide excellent serogroup-specific protection lasting for 2-4 years in adults and children aged more than 2 years. Meningococcal polysaccharide vaccines are now often replaced by conjugate meningococcal vaccines.

Conjugate meningococcal vaccines

Conjugation of the meningococcal polysaccharide to a protein carrier induces a T-cell-dependent immune response characterized by increased immunogenicity among infants, prolonged duration of protection among older children and adults, and reduced nasopharyngeal carriage of meningococci.
Conjugate meningococcal vaccines are available as monovalent serogroup A and serogroup C vaccines, bivalent serogroups A and C vaccine and tetravalent serogroups A, C, Y and W-135 vaccine.
The conjugate vaccines are serogroup-specific and highly immunogenic (>90%). In contrast to group C polysaccharide vaccines, the group C conjugate vaccine elicits adequate antibody responses and immunological memory even in infants who are vaccinated at 2, 3 and 4 months of age.

• A conjugated serogroup A meningococcal vaccine, which was designed particularly for use in the African meningitis belt, is licensed for single-dose immunization of individuals aged 1–29 years.
• Three tetravalent conjugate vaccines against serogroups A, C, Y and W-135 meningococci are now licensed internationally. They differ in the conjugate carrier protein but all are administered ntramuscularly and show similar immunogenicity. These vaccines are licensed for single-dose immunization of individuals 2–55 years of age.
• Although tetravalent vaccines offer the widest range of protection, they do not protect against meningococci of serogroups B and X, which are common causes of meningococcal disease in some countries.

Required vaccinations

Saudi Arabia demands proof of recent meningococcal vaccination (with the tetravalent vaccine) as a visa requirement for pilgrims and guest workers.