A Seroepidemiological Study of Serogroup A Meningococcal Infection in the African Meningitis Belt

Abstract

The pattern of epidemic meningococcal disease in the African meningitis belt may be influenced by the background level of population immunity but this has been measured infrequently. A standardised enzyme-linked immunosorbent assay (ELISA) for measuring meningococcal serogroup A IgG antibodies was established at five centres within the meningitis belt. Antibody concentrations were then measured in 3930 individuals stratified by age and residence from six countries. Seroprevalence by age was used in a catalytic model to determine the force of infection. Meningococcal serogroup A IgG antibody concentrations were high in each country but showed heterogeneity across the meningitis belt. The geometric mean concentration (GMC) was highest in Ghana (9.09 μg/mL [95% CI 8.29, 9.97]) and lowest in Ethiopia (1.43 μg/mL [95% CI 1.31, 1.57]) on the margins of the belt. The force of infection was lowest in Ethiopia (λ = 0.028). Variables associated with a concentration above the putative protective level of 2 μg/mL were age, urban residence and a history of recent vaccination with a meningococcal vaccine. Prior to vaccination with the serogroup A meningococcal conjugate vaccine, meningococcal serogroup A IgG antibody concentrations were high across the African meningitis belt and yet the region remained susceptible to epidemics.

Seroepidemiology: an underused tool for designing and monitoring vaccination programmes in low‐ and middle‐income countries

“…cholera, human papillomavirus, rotavirus, typhoid) or for invasive bacterial infections [ Haemophilus influenzae type b (Hib), meningococcal and pneumococcal infection] where antibodies generated by colonisation complicate the interpretation of seroprevalence data . Nonetheless, serological studies have contributed to elucidating the pre‐vaccination epidemiology of meningococcal A infection in Africa .…”

“…Serosurveillance of meningococcal serogroup C antibodies in the United Kingdom (UK) has shown that antibody levels wane quickly after primary vaccination , highlighted the relationship between waning antibody titres and declining vaccine efficacy and shown the need for a booster dose to be administered . Seroepidemiology is likewise being used to help monitor the impact and duration of immunity after introduction of the new conjugate meningococcal A vaccine in Africa . Diphtheria, once a major cause of childhood mortality in Europe, became uncommon after mass vaccination began and was targeted for elimination from the region by 2000, but a major resurgence occurred in all countries of the former Soviet Union during the 1990s .…”

Meningococcal serogroup B vaccines: Estimating breadth of coverage

“… 68 Differences among laboratories in performing hSBAs can also hinder the ability to compare responses and assessments of breadth of coverage between meningococcal vaccines. 69 Therefore, alternative assays have been proposed to predict vaccine coverage (not efficacy) that are technically easier to perform than SBAs; these approaches are summarized in the following section.…”

“… 78 An IgG meningococcal serogroup A polysaccharide antibody concentration of > 2 μg/mL was considered indicative of protection against MenA disease based on the results of a Finnish clinical study of a meningococcal polysaccharide vaccine conducted nearly 40 y ago, but differences were noted among some populations in the African meningitis belt, where antibody concentrations were generally higher. 69 It has been suggested that much of the antibody detected by this ELISA technique is nonfunctional, potentially because it is induced by cross-reacting bacteria or due to low avidity of the antigen-antibody complex. Limitations regarding the use of ELISA for meningococcal-specific IgG rather than SBA for serogroup C disease have also been discussed in other published studies.…”

Impact of the Meningococcal A Conjugate Vaccine Introduction in the African Meningitis Belt, 2010-2017

“…Meningococcal meningitis is a major public health problem in the 26 countries of the African meningitis belt stretching from Senegal in the west to Ethiopia in the east, where an estimated 430 million people are living [1][2][3][4][5]. Meningococcal meningitis cases occur throughout the world.…”