[Methodology of the 2nd seroprevalence study in Spain]. / Metodología del 2º estudio de seroprevalencia en España.

Seroprevalence studies are designed in population samples to assess the level and distribution of immunity induced by natural infection of certain infectious agents or by immunization against them. The purpose of the 2nd Seroprevalence Study in Spain is to assess the prevalence and distribution of immune status against vaccine-preventable diseases and generated by natural infection by other microorganisms. Pathologies specifically included in the study are: poliomyelitis, diphtheria, tetanus, pertussis, measles, rubella, mumps, varicella, invasive meningococcal disease by serogroup C, hepatitis A, hepatitis B, hepatitis E, hepatitis C and HIV. The study has a similar design of that conducted in 1996, as it is a descriptive cross-sectional study in resident population of 2 to 80 years of age in Spain. Two-stage conglomerate sampling was carried out on the population aged 2 to 80 years living in Spain, with an initial sample size of 10,000 people. The methodology of the study is described in this article.

Los estudios de seroprevalencia se elaboran en muestras poblacionales con el fin de investigar el nivel y distribución de la inmunidad inducida por infección natural de determinados agentes infecciosos o por vacunación frente a los mismos. El 2º Estudio de Seroprevalencia en España tiene el objetivo de estimar la prevalencia y distribución del estado inmune frente a las enfermedades inmunoprevenibles y de la generada por infección natural por otros microrganismos. En concreto, las patologías incluidas en el estudio son: poliomielitis, difteria, tétanos, tosferina, sarampión, rubéola, parotiditis, varicela, enfermedad meningocócica invasora por serogrupo C, hepatitis A, hepatitis B, hepatitis C, hepatitis E e infección por virus de la inmunodeficiencia humana (VIH). Para ello, se ha diseñado un estudio similar al realizado en 1996, observacional de tipo transversal en la población residente en España de 2 a 80 años de edad. Se ha realizado un muestreo por conglomerados bietápico de la población de 2 a 80 años residente en España, con un tamaño muestral inicial de 10.000 personas. En este artículo se describe la metodología utilizada en la realización del estudio.

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

The Global Meningococcal Initiative (GMI) has recently considered current issues in Middle Eastern and African countries, and produced two recommendations: (i) that vaccination of attendees should be considered for some types of mass-gathering events, as some countries mandate for the Hajj, and (ii) vaccination of people with human immunodeficiency virus should be used routinely, because of increased meningococcal disease (MD) risk. Differences exist between Middle Eastern and African countries regarding case and syndrome definitions, surveillance, and epidemiologic data gaps. Sentinel surveillance provides an overview of trends and prevalence of different capsular groups supporting vaccine selection and planning, whereas cost-effectiveness decisions require comprehensive disease burden data, ideally counting every case. Surveillance data showed importance of serogroup B MD in North Africa and serogroup W expansion in Turkey and South Africa. Success of MenAfriVac® in the African "meningitis belt" was reviewed; the GMI believes similar benefits may follow development of a low-cost meningococcal pentavalent vaccine, currently in phase 1 clinical trial, by 2022. The importance of carriage and herd protection for controlling invasive MD and the importance of advocacy and awareness campaigns were also highlighted.

Seroprevalence of antibodies against serogroup C meningococci in the region of Valencia, Spain: Impact of meningococcal C conjugate vaccination.

BACKGROUND AND AIMS: Meningococcal C conjugate (MCC) vaccination programs provide direct and indirect protection against meningococcal disease. However, a decrease in the antibodies could affect herd immunity. We conducted a seroprevalence study to assess the immunity in subjects 8-12years after different MCCV vaccination programs were launched and evaluated the impact of vaccination on seroprotection. METHODS: Seroepidemiological study conducted from October 2010 to April 2012 in the region of Valencia, Spain. Sample size was not proportional to the population but to the expected seroprotection by age group. Sera from subjects that were≥3years old were tested using a standardized complement-mediated serum bactericidal antibodies (SBA) assay. Age-stratified proportions of subjects with SBA titers≥8 were considered seroprotected and evaluated. A multivariate logistic regression model was performed to evaluate the impact of vaccination on the seroprotection. RESULTS: Serum samples from 1880 subjects were collected. In total, 523 (27.8%) of the 1880 subjects and 446 (31.2%) of the 1430 subjects<30years (targeted to any vaccination campaign) showed protective SBA titers. The highest percentage of seroprotected subjects (67.8%, 95%CI 56.9-77.4) was observed in those that were vaccinated in a catch-up campaign at 10-13years of age (20-21years old at the time of blood sampling). Those scheduled for immunization in infancy at 2, 4 and 6months of age (7-8years at blood sample) represented the lowest (7.1%, 95% CI 3.3-13.1) number of seroprotected subjects. Having received one vaccine dose after 12months of age was associated with increased seroprotection. The present study revealed a positive correlation between the increasing age at vaccination and longer duration of seroprotection. CONCLUSION: Only one in three subjects who were vaccinated with MCC vaccine was seroprotected after 8-12years. These findings emphasize that seroprevalence studies are essential to identify susceptible cohorts and to inform vaccine policy.

The Global Meningococcal Initiative: global epidemiology, the impact of vaccines on meningococcal disease and the importance of herd protection.

INTRODUCTION: The 2015 Global Meningococcal Initiative (GMI) meeting discussed the global importance of meningococcal disease (MD) and its continually changing epidemiology. Areas covered: Although recent vaccination programs have been successful in reducing incidence in many countries (e.g. Neisseria meningitidis serogroup [Men]C in Brazil, MenA in the African meningitis belt), new clones have emerged, causing outbreaks (e.g. MenW in South America, MenC in Nigeria and Niger). The importance of herd protection was highlighted, emphasizing the need for high vaccination uptake among those with the highest carriage rates, as was the need for boosters to maintain individual and herd protection following decline of immune response after primary immunization. Expert commentary: The GMI Global Recommendations for Meningococcal Disease were updated to include a recommendation to enable access to whole-genome sequencing as for surveillance, guidance on strain typing to guide use of subcapsular vaccines, and recognition of the importance of advocacy and awareness campaigns.

[Current situation of the epidemiology of meningococcal disease]. / Situación actual de la epidemiología de la enfermedad meningocócica.

Neisseria meningitidis, the etiological agent of all forms of meningococcal disease, is still a cause for concern among society in general and especially among health workers. Several of its antigens have been used in strain characterization, and some have served as the basis for the development of vaccines. In this sense, the best known are the capsular polysaccharide, which defines the serogroups, the outer membrane protein of class 2/3, used for serotype classification, and the class 1 porins, defining the serosubtype. During the last 30 years, most cases of meningococcal disease in Spain have been due to serogroup B strains, with the exception of 1996 and 1997, when serogroup C cases became the most frequent. The capsular polysaccharide has been successfully used in the development of conjugate vaccines highly effective against A, Y and W135 serogroups and particularly against serogroup C isolates. The development of a vaccine against serogroup B strains for routine immunization is still uncertain. However, the use of specific vaccines based on antigenic formulations of class 1 protein, to be applied in epidemic situations, is closer to becoming a reality. Because of the current absence of a universal vaccine against N. meningitidis, specific surveillance programs are required to evaluate the importance of recombination processes affecting capsular expression. This type of event could produce new strain variants able to avoid the immunological response generated after vaccination.