Carriage Rate and Effects of Vaccination after Outbreaks of Serogroup C Meningococcal Disease, Brazil, 2010

Marco Aurelio Palazzi Sáfadi

, Telma Regina Marques Pinto Carvalhanas, Ana Paula de Lemos, Maria Cecilia Outeiro Gorla, Maristela Salgado, Lucila O. Fukasawa, Maria Gisele Gonçalves, Fabio Higa, Maria Cristina Cunto Brandileone, Claudio Tavares Sacchi, Ana Freitas Ribeiro, Helena Keico Sato, Lucia Ferro Bricks, and José Cassio de Moraes

Author affiliations: Faculdade de Ciências Médicas da Santa Casa, São Paulo, Brazil (M.A.P. Sáfadi, J.C. de Moraes); Centro de Vigilância Epidemiológica Alexandre Vranjac, São Paulo (T.R.M.P. Carvalhanas, A.F. Ribeiro, H.K. Sato); Instituto Adolfo Lutz, São Paulo (A.P. de Lemos, M.C.O. Gorla, M. Salgado, M.G. Gonçalves, L.O. Fukasawa, F. Higa, M.C.C. Brandileone, C.T. Sacchi); Sanofi Pasteur Vaccines, São Paulo (L.F. Bricks)

Abstract

During 2010, outbreaks of serogroup C meningococcal (MenC) disease occurred in 2 oil refineries in São Paulo State, Brazil, leading to mass vaccination of employees at 1 refinery with a meningococcal polysaccharide A/C vaccine. A cross-sectional study was conducted to assess the prevalence of meningococci carriage among workers at both refineries and to investigate the effect of vaccination on and the risk factors for pharyngeal carriage of meningococci. Among the vaccinated and nonvaccinated workers, rates of overall meningococci carriage (21.4% and 21.6%, respectively) and of MenC carriage (6.3% and 4.9%, respectively) were similar. However, a MenC strain belonging to the sequence type103 complex predominated and was responsible for the increased incidence of meningococcal disease in Brazil. A low education level was associated with higher risk of meningococci carriage. Polysaccharide vaccination did not affect carriage or interrupt transmission of the epidemic strain. These findings will help inform future vaccination strategies.

In Brazil, meningococcal disease is endemic; 1.5–2.0 cases per 100,000 inhabitants were reported during 2000–2009. Since 2002, a substantial increase has been observed in the proportion of cases attributed to meningococcus serogroup C (MenC) that is associated with the sequence type (ST) 103 complex, and MenC is currently responsible for most cases of meningococcal disease in Brazil (1–3).

Several outbreaks of MenC disease have been reported in Brazil in recent years (2,4–6). To control these outbreaks, chemoprophylaxis is administered to contacts of infected persons, and vaccination is often recommended for persons in age groups at higher risk for infection. In these reactive vaccination campaigns, meningococcal C conjugate (MCC) vaccine use is restricted to children < 2 years of age because of cost and supply issues; meningococcal A/C polysaccharide vaccine is recommended for persons >2 years of age (1–3).

Published data describing meningococci carriage in Brazil are limited. Few studies have been conducted that assess 1) the role of carriage prevalence in the dynamics of carriage and disease or 2) the potential effect of control programs, such as vaccination, on the transmission of meningococci. Thus, we conducted a cross-sectional study with the primary objective of assessing the prevalence of meningococcal carriage among workers at 2 oil refineries in São Paulo State, Brazil, where outbreaks of MenC disease occurred in 2010. We also investigated the effect of meningococcal A/C polysaccharide vaccination and risk factors on pharyngeal carriage of meningococci.