Effect of a serogroup A meningococcal conjugate vaccine (PsA–TT) on serogroup A meningococcal meningitis and carriage in Chad: a community study

Abstract

SummaryBackgroundA serogroup A meningococcal polysaccharide–tetanus toxoid conjugate vaccine (PsA–TT, MenAfriVac) was licensed in India in 2009, and pre-qualified by WHO in 2010, on the basis of its safety and immunogenicity. This vaccine is now being deployed across the African meningitis belt. We studied the effect of PsA–TT on meningococcal meningitis and carriage in Chad during a serogroup A meningococcal meningitis epidemic.MethodsWe obtained data for the incidence of meningitis before and after vaccination from national records between January, 2009, and June, 2012. In 2012, surveillance was enhanced in regions where vaccination with PsA–TT had been undertaken in 2011, and in one district where a reactive vaccination campaign in response to an outbreak of meningitis was undertaken. Meningococcal carriage was studied in an age-stratified sample of residents aged 1–29 years of a rural area roughly 13–15 and 2–4 months before and 4–6 months after vaccination. Meningococci obtained from cerebrospinal fluid or oropharyngeal swabs were characterised by conventional microbiological and molecular methods.FindingsRoughly 1·8 million individuals aged 1–29 years received one dose of PsA–TT during a vaccination campaign in three regions of Chad in and around the capital N'Djamena during 10 days in December, 2011. The incidence of meningitis during the 2012 meningitis season in these three regions was 2·48 per 100 000 (57 cases in the 2·3 million population), whereas in regions without mass vaccination, incidence was 43·8 per 100 000 (3809 cases per 8·7 million population), a 94% difference in crude incidence (p<0·0001), and an incidence rate ratio of 0·096 (95% CI 0·046–0·198). Despite enhanced surveillance, no case of serogroup A meningococcal meningitis was reported in the three vaccinated regions. 32 serogroup A carriers were identified in 4278 age-stratified individuals (0·75%) living in a rural area near the capital 2–4 months before vaccination, whereas only one serogroup A meningococcus was isolated in 5001 people living in the same community 4–6 months after vaccination (adjusted odds ratio 0·019, 95% CI 0·002–0·138; p<0·0001).InterpretationPSA–TT was highly effective at prevention of serogroup A invasive meningococcal disease and carriage in Chad. How long this protection will persist needs to be established.FundingThe Bill & Melinda Gates Foundation, the Wellcome Trust, and Médecins Sans Frontères.

Persistence of the immune response after MenACWY-CRM vaccination and response to a booster dose, in adolescents, children and infants

“…21 Indeed, while both assays have been used variably across clinical studies for meningococcal vaccines, several studies of antibody persistence preferentially utilize the rSBA assay. 42,46 A correlation between elevated rSBA titers and protection against serogroup A IMD was also recently suggested by epidemiologic surveillance studies conducted in Africa after a mass-vaccination campaign using the meningococcal serogroup A conjugate vaccine MenAfriVac Ò . After the vaccination campaign, in the setting of elevated rSBA antibody titers in the population, there were no new cases of IMD, and rates of serogroup A carriage were low.…”

Meningococcal disease in the Middle East and Africa: Findings and updates from the Global Meningococcal Initiative

“…Carriage of MenA was substantially reduced in areas where vaccination had been introduced (by 98% in Chad). 35 In addition, MenAfriVac Ò uses tetanus toxin as a carrier, and some serologic data have suggested protection against tetanus. 54 In 2010e2012, MenW disease reemerged in Burkina Faso.…”

The contribution of vaccination to global health: past, present and future

“…However, there is increasing recognition that the public health benefits provided by vaccination are [28] and immunization of older children and young adults against meningococcal disease in the African meningitis belt through mass campaigns [29].…”