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In face of evidence of rapid waning of vaccine effectiveness against Omicron and its sub-lineages, a second booster with mRNA vaccines was recommended for the most vulnerable in France. We used a test negative design to estimate the effectiveness of the second booster relative to the first booster and the protection conferred by a previous SARS-CoV-2 infection, against symptomatic Omicron BA.2 or BA.4/5. We included symptomatic ≥60 years old individuals tested for SARS-CoV-2 in March 21-October 30, 2022. Compared to a 181-210 days old first booster, a second booster restored protection with a relative effectiveness of 39% [95%CI: 38% - 41%], 7-30 days post-vaccination This gain in protection was lower than the one observed with the first booster, at equal time points since vaccination. High levels of protection were associated to previous SARS-CoV-2 infection, especially if the infection was recent and occurred when an antigenic-related variant was dominant.HighlightsA second Wuhan-like mRNA booster brought additional protection against symptomatic Omicron BA.2 or BA.4/5 infections, relative to a first booster given 181 to 210 days ago.The gain in protection offered by a second booster was lower to the protection observed with a first booster, at equal time points since these booster doses.Previous infection, in a vaccinated population, offered high levels and long-lasting protection against symptomatic Omicron BA.2 or BA.4/5 infections.

Since the emergence of Omicron, reinfections with SARS-CoV-2 have been rising. We estimated the risk of SARS-CoV-2 reinfection in the widely vaccinated French population, from January to August 2022. At nine weeks post-infection, the relative risk of reinfection, primary infection with pre-Delta variants being the reference group, was estimated at 0.43 [95%CI 0.40-0.47] if the primary infection was attributed to Delta, 0.21 [95%CI 0.19-0.24] with BA.1 and 0.17 [95% CI 0.15-0.18] with BA.2, and rapidly waned overtime. After a BA.1 primary infection the protection was similar against BA.2 or BA.4/5 reinfection.

International audience; Since the first reports in summer 2020, SARS-CoV-2 reinfections have raised concerns about the immunogenicity of the virus, which will affect SARS-CoV-2 epidemiology and possibly the burden of COVID-19 on our societies in the future. This study provides data on the frequency and characteristics of possible reinfections, using the French national COVID-19 testing database. The Omicron variant had a large impact on the frequency of possible reinfections in France, which represented 3.8% of all confirmed COVID-19 cases since December 2021.

Changing epidemiology of meningococcal disease. The epidemiology of invasive meningococcal disease (IMD) is characterized by a marked variation in incidence and serogroup distribution by geographical region and over time. Immunization programs against serogroups A, C, W, Y in adolescents in North America or mass vaccination campaigns against serogroup A in Sub-Saharan Africa reduced the disease burden in these affected areas. In Europe, immunization against serogroup C in several countries has been successful in reducing incidence through direct and indirect effect. In France, surveillance of IMD is based on mandatory notification and strain genetic characterization at the National reference Center for meningococci. Despite its low incidence (between 0.7 and 1.6 cases per 100,000 people), the disease remains of public health concern because it affects mostly young children and the case fatality rate is around 10%. The rates of vaccination coverage for serogroup C vaccines remain insufficient, particularly among adolescents, to induce herd immunity.Évolution de l’épidémiologie des infections invasives à méningocoques. L’épidémiologie des infections invasives à méningocoques se caractérise par une variation de l’incidence et de la distribution des sérogroupes en fonction des régions géographiques et des années. Des programmes de vaccination des adolescents contre les sérogroupes A, C, W et Y en Amérique du Nord ou des campagnes de vaccination de masse contre le sérogroupe A en Afrique subsaharienne ont réduit le poids de la maladie dans les régions concernées. En Europe, la vaccination contre le méningocoque C dans plusieurs pays a permis de réduire de façon importante l’incidence de la maladie par effets direct et indirect de la vaccination. En France, la surveillance des infections repose sur la déclaration obligatoire et la caractérisation génotypique des méningocoques invasifs au Centre national de référence des méningocoques. Même si l’incidence des infections invasives à méningocoques est basse (entre 0,7 et 1,6 cas pour 100 000 habitants), la maladie reste une préoccupation de santé publique du fait des taux d’incidence élevés chez les jeunes enfants et de la mortalité (10 % en moyenne). Les niveaux de couverture vaccinale contre le méningocoque C restent encore insuffisants, notamment chez les adolescents, pour induire une immunité de groupe.

International audience; BACKGROUND:Neisseria meningitidis group W (NmW) belonging to the clonal complex ST-11 (NmW/cc11) spread in Europe and in France in 2000 and declined thereafter. In France, invasive meningococcal disease (IMD) due to NmW increased again in 2012 and thereafter since 2015. Several sub-lineages of NmW/cc11 are circulating worldwide with successive epidemic waves. We aimed to describe recent epidemiological trends of NmW in France and to explore the microbiological and epidemiological characteristics associated with different NmW/cc11 sub-lineages.METHODS:The epidemiology of NmW was described based on data collected through mandatory notification of IMD and strain typing data for culture-confirmed and PCR-confirmed cases for the period 2000-2016. All culture-confirmed cases due to NmW from the period 2010-2016 were characterised by whole genome sequencing (WGS). A detailed epidemiological analysis was performed for culture-confirmed cases on the basis of WGS data.FINDINGS:During the period 2010-2016, genotyping was obtained for 148 cases including all the 132 culture-confirmed cases, among which 127 were matched with epidemiological data, and 16 PCR-confirmed cases (out of a total of 47 PCR-confirmed cases). An increase in IMD was observed in 2012 and was linked to isolates belonging to the "Anglo-French-Hajj" sub-lineage. These isolates have decreased significantly since 2013 and have been replaced by NmW/cc11 isolates related to the "South American - UK" sub-lineage which caused a marked increase in the number of cases of NmW in 2016. In this sub-lineage, the "original UK strain" was first detected in 2012 and increased thereafter, followed by the recently described "UK 2013-strain". Isolates related to the "South American-UK" sub-lineage represented 45% of all NmW cultured isolates from the whole period 2010-2016 but were the most frequent isolates in 2016, representing 76% of the total NmW typed isolates and 94% of the typed NmW/cc11 isolates. A changing pattern in the epidemiology of NmW has been observed in 2015-2016 in relation to the spread of the "UK 2013-strain" with a sharp increase in the number of cases among persons aged 15 years and over and a high case fatality rate (CFR). Among cases due to the "UK 2013-strain", 94% of cases were aged 15 years and over and the CFR was 28%.INTERPRETATION:Our data suggest a recent clonal replacement among NmW/cc11 isolates with the expansion of the "South American-UK" sub-lineage in France and particularly the "UK 2013-strain" which was predominant in 2015 and 2016. A shift in the age-distribution of IMD due to NmW to older ages and the high CFR are consistent with the expansion of a new virulent clone in a naive population. These data may have an impact on tailoring vaccination strategies against NmW.

International audience; Meningococci spread via respiratory droplets, whereas the closely related gonococci are transmitted sexually. Several outbreaks of invasive meningococcal disease have been reported in Europe and the United States among men who have sex with men (MSM). We recently identified an outbreak of serogroup C meningococcal disease among MSM in Germany and France. In this study, genomic and proteomic techniques were used to analyze the outbreak isolates. In addition, genetically identical urethritis isolates were recovered from France and Germany and included in the analysis. Genome sequencing revealed that the isolates from the outbreak among MSM and from urethritis cases belonged to a clade within clonal complex 11. Proteome analysis showed they expressed nitrite reductase, enabling anaerobic growth as previously described for gonococci. Invasive isolates from MSM, but not urethritis isolates, further expressed functional human factor H binding protein associated with enhanced survival in a newly developed transgenic mouse model expressing human factor H, a complement regulatory protein. In conclusion, our data suggest that urethritis and outbreak isolates followed a joint adaptation route including adaption to the urogenital tract.

Background Since 2011 public concerns about Human Papillomavirus (HPV) vaccination safety and efficacy arose in France. We explored the relevance of using vaccines reimbursement data to assess the impact of those public concerns on vaccination coverage. Methods We used the Permanent Sample of Beneficiaries which was, at the time of the study, a representative sample of 1/97th health insurance beneficiaries of the main Social Security scheme, the General Health Insurance Scheme, covering approximately 77 % of the French resident population. We estimated HPV vaccination coverage among girls born between 1995 and 1999 at their 15th, 16th and 17th birthday. Results The coverage for complete vaccination among 16 years old girls decreased from 26.5 % in the first semester of 2011 to 18.6 % in the first semester of 2014. Conclusions HPV vaccination coverage was already low in 2011 and continued to decrease thereafter. Vaccines reimbursement data allowed us to reactively monitor the impact of the controversy on vaccination coverage and design counteracting measures.

Rubella is an acute infectious disease that normally has a mild clinical course. However, infections during pregnancy, especially before week 12 of gestation (WG), can cause severe birth defects known as congenital rubella syndrome (CRS). The aim of this study was to perform genotyping and molecular characterization of rubella viruses involved in congenital infections in France over the past 15 years (1995 to 2009). Amniotic fluid (AF) specimens ( n = 80) from pregnant women with congenital rubella infections (CRI) before week 20 of gestation, and a few other samples available from children/newborns with CRS ( n = 26), were analyzed. The coding region of the rubella virus E1 gene was amplified directly from clinical specimens by reverse transcriptase PCR, and the resulting DNA fragments were sequenced. Sequences were assigned to genotypes by phylogenetic analysis with rubella virus reference sequences. Sufficient E1 gene sequences were obtained from 56 cases. Phylogenetic analysis of the sequences showed that at least five different genotypes (1E, 1G, 1B, 2B, and 1h) were present in France and were involved in congenital infections, with a strong predominance of genotype 1E (87%). This is one of the very few comprehensive studies of rubella viruses involved in CRI. The results indicated that over the past 15 years, multiple introductions of the dominant genotype E caused most of the CRI cases in France. A few sporadic cases were due to other genotypes (1B, 1G, 1h, 2B).

In 2008, measles reappeared in France in a series of outbreaks. During this period, 604 measles cases were reported to a routine surveillance system and 305 (50%) of these cases were then confirmed in the laboratory. To understand better the current epidemiological situation and the circulation of different measles strains, a phylogenetic characterization of 113 (19%) of the measles cases from these outbreaks was performed. All measles cases met the WHO clinical criteria and were confirmed either by laboratory detection of measles-specific IgM and/or by detection of the virus genome by polymerase chain reaction (PCR) and viral isolation. PCR products generated from blood, oral fluid, urine, or nasopharyngeal-swab samples were sequenced for molecular epidemiology studies. Phylogenetic analysis showed a co-circulation of genotypes D4 and D5 during the first measles outbreak in the city of Reims in early 2008. Over the course of the year, the A, B3.2, D8, and D9 genotypes also appeared. The data from this study show the simultaneous circulation of several measles genotypes in France and describe genotypes D8 and D9 for the first time in this country. The data also suggest that there are still many pockets of unvaccinated individuals helping to maintain the circulation of measles virus in the population. Phylogenetic studies allowed the corroboration of epidemiologic links and showed that nosocomial transmission can create significant risk for measles dissemination. Finally, the pattern of changes in viral genotypes during 2008 suggests a regular introduction of measles strains from abroad. J. Med. Virol. 82:1033–1043, 2010. © 2010 Wiley-Liss, Inc.

Background Cytomegalovirus (CMV) is the most frequent cause of congenital viral infection in developed countries. Objectives The objective of this study was to evaluate the impact of our prenatal CMV infection screening and counseling policy. Study design Since 2005, all pregnant women in our obstetric center have been informed about CMV infection, and if they agree, given a serological test at around 12 weeks of gestation (WG). If this first test is negative, the women and their partners are given hygiene counseling on how to prevent CMV infection, and a second test is performed at around 36 WG. Results Among the 5312 women who had an unknown immune status, or were known to be seronegative when they had their first visit to our center for their current pregnancy, 97.4% agreed to CMV screening. Primary infection was detected in 11 women between 0 and 12 WG (0.42%), and seroconversion was diagnosed in five women between 12 and 36 WG (0.19%). Conclusions These results suggest that if clear information is given on CMV infection during pregnancy, the rate of seroconversion is lower following counseling than before counseling.

Background. Public health and clinical strategies for meningitis epidemics in sub-Saharan Africa usually assume that Neisseria meningitidis infection causes most disease. Methods. During 24 months from 2002 to 2005, we collected clinical and laboratory information for suspected acute bacterial meningitis cases from 3 districts in Burkina Faso. Streptococcus pneumoniae was identified by culture, polymerase chain reaction, or antigen detection in cerebrospinal fluid. Pneumococcal genotyping was performed on strains using multilocus variable-number tandem repeat typing and multilocus sequence typing. Results. Samples of cerebrospinal fluid were collected from 1686 persons; 249 (15%) had S. pneumoniae identified (annual incidence, 14 cases per 100,000 persons). Of these patients, 115 (46%) died, making S. pneumoniae the most commonly identified organism and responsible for two-thirds of deaths due to bacterial meningitis. During the meningitis epidemic season, an average of 38 cases of S. pneumoniae infection were identified each month, compared with an average of 8.7 cases during other months. Of 48 pneumococci that were tested, 21 (44%) were identified as serotype 1, and the remaining 27 (56%) were identified as 15 different serogroups and/ or serotypes. Both serotype 1 and other serogroups and/or serotypes were seasonal. The genotypes of serotype 1 isolates were closely related but diversified over the study period and were similar to, but not identical to, the predominant genotypes found previously in Ghana. Conclusions. Intervention strategies during the epidemic season in Burkina Faso (and perhaps elsewhere) must now account for pneumococcal meningitis occurring in an epidemic pattern similar to meningococcal meningitis. Although a serotype 1 clone was commonly isolated, over half of the cases were caused by other serogroups and/ or serotypes, and genetic diversification increased over a relatively short period.

We analyzed 48 invasive isolates of Neisseria meningitidis that were isolated from meningitis cases in Burkina Faso (April 2002 to April 2003). Thirty-nine of these isolates had the phenotype (serogroup:serotype:serosubtype) W135:2a:P1.5,2, eight isolates were A:4:P1.9 and one isolate was nongroupable:nonserotypable:nonserosubtypable. Genotyping of meningococcal isolates showed that W135 isolates belonged to the sequence type (ST)-11. The nongroupable isolate was of genogroup W135 and belonged to ST-192. Isolates of serogroup A belonged to ST-2859 (a member of the subgroup III/ST-5 clonal complex). W135 (ST-11) isolates involved in meningitis outbreaks in Burkina Faso differed from those involved in the Hajj-2000 associated outbreak by their pulsed-field gel electrophoresis profile. These data confirm the changing epidemiology of meningococcal infection in Burkina Faso with the establishment and expansion of serogroup W135 N. meningitidis strains of the ET-37/ST-11 clonal complex, as well as the emergence of a new clone within the subgroup III/ST-5 clonal complex.

A controlled study was conducted in Karachi, Pakistan to compare humoral and mucosal immune responses against polioviruses in infants who received oral poliovirus vaccine (OPV) at birth and at 6, 10, and 14 weeks according to the Expanded Program on Immunization (EPI) with infants who received either three doses of inactivated poliovirus vaccine (IPV) at 6, 10, and 14 weeks together with OPV or one additional dose of IPV at 14 weeks together, with the last dose of OPV. A total of 1429 infants were enrolled; 24-week serum specimens were available for 898 infants (63%). They all received a challenge dose of OPV type 3 at 24 weeks of age. The addition of three doses of IPV to three doses of OPV induced a significantly higher percentage of seropositive children at 24 weeks of age for polio 1 (97% versus 89%, P

2,a Although France has had a vaccination program for 40 years, since 1990, an increase in whooping cough cases with parent-infant transmission has been observed. This study prospec- tively assessed the frequency of Bordetella pertussis infection in adults who consulted general practitioners for a persistent cough without an evident diagnosis. Among 217 patients, 70 (32%) confirmed whooping cough cases were identified. One case was culture positive, 36 were poly- merase chain reaction positive, and 40 had increases or decreases of 2-fold in anti-pertussis toxin IgG titer between serum samples collected during the acute and convalescent phases. The median duration of cough in confirmed cases was 49 days (range, 13-123 days). Of the patients, 60% reported vaccination, and 33% reported whooping cough in infancy. Pertussis should be considered for diagnosis of acute and chronic cough in adults. Future studies should evaluate the public health interest of booster doses of pertussis vaccine in adults. Whooping cough, the principal symptom of which is a pro- longed cough, is caused by the gram-negative bacterium Bor- detella pertussis. Many studies have reported that clinical whoop- ing cough in adolescents or adults, although milder or atypical, may cause prolonged illness, which may lead to the infection of

A new needleless jet-injector, Mini-Imojet, was developed that administers liquid vaccines from a single-use, pre-filled cartridge named Imule, which avoids the risk of cross-contamination. We conducted clinical trials in several settings in France and West Africa to compare the immunogenicity and tolerance of five vaccines (influenza vaccine, Vi capsular polysaccharide typhoid vaccine, tetanus toxoid vaccine, diphtheria-tetanus-whole cell pertussis vaccine, and inactivated hepatitis A vaccine) administered with the Imule system vs standard syringe technique. In each vaccine study, all subjects of either group were tested for serum antibody titres to calculate the geometrical mean titres and seroconversion rates after complete vaccination. Immediate local-reactions were noted after each injection, and local and general reactions were evaluated during a predetermined period of follow-up. When delivered by the Imule technique, all the administered vaccines were of equivalent or superior immunogenicity, compared to the syringe technique. The tolerance to vaccines injected by the Imule system was acceptable in all studies. The most frequently observed reactions were mild (e.g. minor bleeding, superficial papules, erythema and induration) and could be considered to be inherent to the injection technique. The technical and safety advantages of the Mini-Imojet/Imule system, compared to sterilizable, standard disposable or autodestruct syringes and to classical multi-dose vial jet-injectors, reinforces the interest of this new injection technique for collective immunizations.

The diagnostic value of RT-PCR of amniotic fluid (AF) for prenatal diagnosis of congenital rubella virus infection in 45 pregnant women with confirmed primary infection was assessed. Specificity of RT-PCR was 100% and sensitivity ranged between 83 and 95%.

Erratum in Lancet Infect Dis. 2011 Jul;11(7):495.; International audience; BACKGROUND:Outer-membrane-vesicle vaccines for meningococcal B outbreaks are complex and time consuming to develop. We studied the use of already available vaccine to control an outbreak caused by a genetically close strain.METHODS:From 2006 to 2009, all individuals younger than 20 years living in the region of Normandy, France, in which an outbreak caused by a B:14:P1.7,16 strain occurred, were eligible to receive MenBvac, a Norwegian vaccine designed 20 years earlier against a strain sharing the same serosubtype (B:15:P1.7,16). The immunogenicity (in a randomly selected cohort of 400 children aged 1-5 years), safety, and epidemiological effect of the vaccination were assessed.FINDINGS:26,014 individuals were eligible to receive the vaccine. Shortage of vaccine production prompted start of the campaign in the highest incidence groups (1-5 years). 16,709 (64%) received a complete vaccination schedule of whom 13,589 (81%) received a 2+1 dose schedule (week 0, week 6, and month 8). At 6 weeks after the third dose, of 235 vaccinees for whom samples were available, 206 (88%) had a seroresponse, and 108 (56 %) of 193 had a seroresponse at 15 months. These results were similar to those described for tailor-made vaccines and their homologous strain. Only previously described adverse effects occurred. The incidence of B:14:P1.7,16 cases decreased significantly in the vaccine targeted population after the primary vaccination period (from 31·6 per 100,000 to 5·9 per 100,000; p=0·001).INTERPRETATION:The ready-to-wear approach is reliable if epidemic and vaccine strains are genetically close. Other meningococcal B clonal outbreaks might benefit from this strategy; and previously described outer-membrane-vesicle vaccines can be effective against various strains.

Cytomegalovirus (CMV) is the most frequent cause of congenital viral infection in developed countries.The objective of this study was to evaluate the impact of our prenatal CMV infection screening and counseling policy.Since 2005, all pregnant women in our obstetric center have been informed about CMV infection, and if they agree, given a serological test at around 12 weeks of gestation (WG). If this first test is negative, the women and their partners are given hygiene counseling on how to prevent CMV infection, and a second test is performed at around 36 WG.Among the 5312 women who had an unknown immune status, or were known to be seronegative when they had their first visit to our center for their current pregnancy, 97.4% agreed to CMV screening. Primary infection was detected in 11 women between 0 and 12 WG (0.42%), and seroconversion was diagnosed in five women between 12 and 36 WG (0.19%).These results suggest that if clear information is given on CMV infection during pregnancy, the rate of seroconversion is lower following counseling than before counseling.

Large epidemics of group A meningococcal meningitis occurred in 1995 and 1996 in several countries of the Sub-Saharan Africa zone known as the "meningitis belt", and more particularly in West Africa. Most of these countries affected by the epidemics met difficulties to set up the strategy recommended by the World Health Organization and which includes: Epidemiological surveillance and epidemic incidence threshold calculation to detect early meningitis epidemics and emergency vaccination campaigns with meningococcal A + C polysaccharide vaccine, if possible within the 4-to-6 weeks following the moment the threshold is reached. In this context of epidemics, notably in Mali, and in front of the risk of resurgence of yellow fever, the Ministry of Health of Senegal decided to conduct mass preventive immunization campaigns in 1997 against meningo- coccal meningitis and yellow fever in the districts located in the eastern part of the country and where emergency vaccination would have been difficult in case of epidemic because these area are difficult to reach. A short-term microeconomic evaluation of additional costs that are necessary to organize one of these mass preventive immunization campaigns was conducted in 1997 in the Matam District, in the Northeast part of Senegal. The method rested on value attribution and accounting procedure. The cost was defined as the monetary value of all mobilized resources to product the campaign corresponding to a plurality of charges and representing all of the effective expenses and donations. During this campaign, 85,925 people were vaccinated and a total number of 163,981 doses of both polysaccharide A + C meningococcal and yellow fever vaccines were administered within 3 weeks. Four intervention strategies were involved: Three for vaccination (mobile, fixed and outreach strategy) and one for coordination, information and training. The total cost of the campaign was 55,322.75 euros. Vaccines and solvents represented 60% of the total cost of the campaign, materiel for injection and safety of injection 26%, vaccination staff 7%, and logistics 7%. The mean cost was 0.34 euro per administered dose and 0.64 euro per vaccinee. The mean cost per administered dose of meningococcal vaccine was 0.44 euro. The mean cost of preventive meningococcal immunization was not higher than the mean cost of meningococcal vaccination during mass emergency immunization campaigns in other countries. The addition of yellow fever antigen brought down the campaign mean cost by 0.11 euro and it allowed economies of scales. Direct unit costs per administered dose were higher when people were vaccinated through the outreach strategy (0.35 euro) than when fixed and mobile strategies were used (0.318 and 0.323 euro, respectively). Costs related to transportation and staff were proportionally higher for the outreach strategy. Direct unit costs per administered dose were higher when vaccinations were done in rural areas (0.32 euro) than when done in urban areas (0.31 euro). Direct unit costs increased when the size of target communities decreased (in communities with less than 100 people to vaccinate versus 0.38 euro in communities with more than 2,000 people to vaccinate). This study allowed us to set up a method to measure, describe and analyze the costs of a mass preventive campaign. It demonstrated the economic impact of using multiple antigens during a single preventive campaign.

International audience; The aim of the study was to analyze the impact of MenBvac, an outer membrane vesicle (OMV) vaccine against P1.7,16 strains, on meningococcal carriage. During a B:14:P1.7,16/ST-32 outbreak in Normandy (France), children aged 1-7 years were randomly selected to participate in the study. Among the 1082 volunteers, there were 17 Neisseria meningitidis carriers (carriage rate of 1.57%). MenBvac vaccination appeared associated with lower carriage rate, i.e., 0.31% among the vaccinated children versus 2.10% among the non-vaccinated (p=0.03). The beneficial effect on carriage was observed regardless of the strain serogroup. OMV-vaccinated mice also showed reduction of bacterial acquisition of OMV-homolog and hererolog strains in respiratory pathways after intranasal challenge. These results suggest that meningococcal OMV-based vaccines reduce meningococcal carriage and may hence confer herd immunity.

International audience; The aim of this study performed in Normandy, France, was to analyze the pharyngeal meningococcal carriage at the peak of a clonal meningococcal B outbreak, which was subsequently controlled using an outer membrane vesicle vaccination. This cross-sectional study included randomly selected subjects aged 1-25 years. Carriers and non carriers were compared using unconditional logistic regression. Among the 3,522 volunteers, there were 196 (standardized rate: 6.46 %) Neisseria meningitidis carriers, of which there were only five with the outbreak strain (B:14:P1.7,16/ST-32; standardized rate: 0.18 %). From the multivariate analysis, older age, smoking, higher degree of socialization, and social deprivation appear to favor the carriage of all the strains included. Prior antibiotic treatment up to 12 months before swabbing, even with β-lactam, was protective against carriage. Our data indicate a low overall meningococcal carriage rate with a surprising protective effect of prior antibiotic exposure. The observed low carriage rate of the epidemic strain (B:14:P1.7,16/ST-32) contrasts with the high incidence of invasive meningococcal diseases (IMD) due to this strain. Hence, our data underline the high virulence of the strain and suggest a low level of natural immunity of the population against this strain. Although highly resource-consuming, carriage studies are helpful in guiding the implementation of control measures of IMD, such as mass vaccination or chemoprophylaxis.