W135 Meningococcal Disease: A New Vaccine for Africa

Abstracts & Commentary

Synopsis: A case of Neisseria meningitidis W135 in a traveler to Morocco is reported, but it was last year’s epidemic of W135 meningococcal meningitis in Burkina Faso that led to the development of a new trivalent vaccine (A/C/W135) for use in Africa. So far this year, more than 500 deaths due to meningitis have occurred in Burkina Faso.

Sources: Wilder-Smith A, et al. J Travel Med. 2003;10:59-61; WHO CSR and Epidemiological Bulletin, 7 March 2003. www.who.int/csr/don/en/.

A healthy British journalist flew from London to Morocco. She remained in Morocco for 10 days before traveling on to Japan. After an 11-day stay in Japan, she flew to Singapore. During the flight, she began having fever, chills, and rigors. After arrival, she went to her hotel and was later found semiconscious by her friend. On admission to the hospital, she was in shock with a generalized petechial rash. Antibiotics were begun and her CSF culture subsequently grew Neisseria meningitidis W135. She recovered fully and eventually returned home to England.

Wilder-Smith and associates postulate that this traveler was most likely exposed to N meningitidis W135 in Morocco, a predominantly Muslim country. However, exposure from close proximity to a W135 carrier during her airplane travel is another possibility they discussed. Their search of the literature did not reveal any previous reports of W135 meningitis in either Morocco or Japan. Singapore has reported W135 disease, but all cases have been related to the Hajj pilgrimage or close contacts of returning pilgrims.

The Ministry of Health in Burkina Faso has reported a total of 3691 cases of meningococcal disease with 542 deaths since the outbreak began in January 2003. Samples from the outbreaks confirm N meningitidis serogroups A and W135. The number of cases and deaths will no doubt continue to rise. By April of last year, Burkina Faso had reported a total of 11,247 meningitis cases with at least 1300 deaths. N meningitidis W135 was confirmed in 147 of the 175 positive specimens sent to their national laboratory network. The remaining specimens were either serogroup A, or both A + W135 agglutination.1

Comment by Mary-Louise Scully, MD

Meningococcal disease associated with large epidemics in the African "meningitis belt" has historically been caused by N meningitidis serogroup A and, less often, serogroup C strains. Recent reports of significant meningococcal disease outside the traditional "belt" of Africa should heighten our awareness of the growing meningococcal disease risk in other parts of Africa.2,3 The case of W135 meningitis in the British traveler to Morocco perhaps reflects future changes in the epidemiology of African meningococcal disease and its implications for travelers. The epidemic potential of N meningitidis W135 became evident during the 2000 and 2001 Hajj seasons when W135 meningitis occurred in Saudi Arabia and internationally in Hajj pilgrims and their contacts. As a result, vaccination with quadrivalent (A/C/Y/W135) vaccine is now a requirement for a Hajj visa.4 Some postulate that Muslims from Africa introduced this strain to the Hajj pilgrimage. Indeed, sporadic disease due to N meningitidis W135 has been reported in Africa since 1981 and a vaccine trial in 1996 found high levels of W135 carriage in asymptomatic Gambian children.5 Molecular analysis of the W135 Hajj-associated isolates found this strain to be associated with the ET-37 complex, a clone that has been circulating globally since at least 1970.6

The 2002 outbreak of W135 meningitis in Burkina Faso was the first report of epidemic disease in Africa due to this strain. Until now, available international meningococcal polysaccharide vaccines were either monovalent, bivalent (A/C) or quadrivalent (A/C/Y/W135). However, the cost of the quadrivalent vaccine ranges from $4 to $50 per dose and is out of reach for most African countries. Three group C meningococcal conjugate vaccines (MCC) are licensed internationally. MCC is now part of the national immunization program in the United Kingdom and has resulted in a significant reduction in group C meningococcal disease in their country. Unfortunately, none of these vaccines provides protection against serogroup B meningococci strains circulating in Australia, Europe, North America, and South America. Group B polysaccharide is poorly immunogenic, even when conjugated to a protein carrier.

In response to the unexpected 2002 outbreak of W135 meningitis in Burkina Faso, the World Health Organization (WHO) and its partners in meningitis preparedness began intense negotiations to provide an affordable W135 meningitis vaccine to African countries. With unprecedented speed, the WHO, GlaxoSmithKline, and the Bill & Melinda Gates Foundation are making available a new trivalent vaccine to cover serogroups A, C, and W135. Already 500,000 doses of the newly licensed trivalent vaccine (A/C/W135) have arrived in Burkina Faso and a mass vaccination campaign is underway in hopes of abating the outbreak now in progress. In all, 3 million doses of the new trivalent vaccine will be available at reduced cost to African countries.7 The vaccine is being distributed through the International Coordinating Group on Vaccine Provision for Epidemic Meningitis Control (ICG) to countries that submit requests and meet the criteria for a meningococcal outbreak. 

References

1. Meningococcal disease, serogroup W135, Burkina Faso. Preliminary Report, 2002. Wkly Epidemiol Rec. 2002; 77:152-155.

2. Molesworth AM, et al. Trans R Soc Trop Med Hyg. 2002;96:242-249.

3. Fischer PR. Travel Medicine Advisor Update. 2002; 12:33-35.

4. Gold R. Clin Infect Disease. 2003;36:684-686.

5. MacLennan JM, et al. Lancet. 2000;356:1078.

6. Mayer L, et al. J Infect Dis. 2002;185:1596-1605.

7. www.who.int/mediacentre/release/2003/pr9/en/print.html.

Dr. Scully, Seattle, WA.