Carriage of serogroup W-135, ET-37 meningococci in The Gambia: Implications for immunisation policy?

We found high levels of symptomless carriage of hyperinvasive Neisseria men ingitidis strain (electrophoretic type 37 [ET-37], serogroup W-135) during a vaccine trial in Gambian children in 1996. Serogroup C, ET-37 complex men ingococci cause 30-40% of meningococcal disease in countries such as the UK , and have a point prevalence of 0.5-1.0%. The recent Hai-associated spread of serogroup W-135, FT-37 complex meningococci, which has been accompanied by numerous secondary cases, might be explained by the apparently raised c arriage rates reported here.