Vaccine Preventability of Meningococcal Clone,Greater Aachen Region,Germany

Emergence of serogroup B meningococci of clonal complex sequence type (ST) 41/44 can cause high levels of disease, as exemplified by a recent epidemic in New Zealand. Multiplication of annual incidence rates (3.1 cases/100,000 population) of meningococcal disease in a defined German region, the city of Aachen and 3 neighboring countries (Greater Aachen) prompted us to investigate and determine the source and nature of this outbreak. Using molecular typing and geographic mapping, we analyzed 1,143 strains belonging to ST41/44 complex, isolated from persons with invasive meningococcal disease over 6 years (2001–2006) from 2 German federal states (total population 26 million) and the Netherlands. A spatially slowly moving clone with multiple-locus variable-number tandem repeat analysis type 19, ST42, and antigenic profile B:P1.7–2,4:F1–5 was responsible for the outbreak. Bactericidal activity in serum samples from the New Zealand MeNZB vaccination campaign confirmed vaccine preventability. Because this globally distributed epidemic strain spreads slowly, vaccination efforts could possibly eliminate meningococcal disease in this area.     

From secondary prevention to primary prevention: a unique strategy that gives hope to a country ravaged by meningococcal disease

New Zealand has been affected by an epidemic of group B meningococcal disease dominated by a strain defined as, B:4:P1.7b,4. Over 5550 cases and 222 deaths have been reported since 1991 in a population of 4 million people.Meningococcal disease cases notified on EpiServ database operated by Institute of Environmental Science and Research Limited through to 30 September 2004. Through the collaborative efforts of a government agency, vaccine company, university and laboratory institute, clinical trials of the Chiron produced outer membrane vesicle (OMV) strain-specific MeNZB vaccine were run in rapid succession. The delivery of MeNZB will be New Zealand's largest immunisation programme with three doses given at 6-week intervals to over 1 million people aged 6 weeks-19 year olds inclusive. Planning, co-ordinating and delivering the immunisation programme is a challenging project for the New Zealand Health Sector.     

Evaluation of serogroup A meningococcal vaccines in Africa: a demonstration project

Endemic and epidemic meningococcal disease constitutes a major public-health problem in African countries of the 'meningitis belt' where incidence rates of the disease are many-fold higher (up to 25 cases per 100,000 population) than those in industrialized countries, and epidemics of meningococcal disease occur with rates as high as 1,000 cases per 100,000 people. Using the precedent established during the licensing of conjugate vaccines against Haemophilus influenzae type b and serogroup C meningococci and components of currently-licensed meningococcal polysaccharide vaccines, new meningococcal conjugate vaccines will likely be licensed using immunological endpoints as surrogates for clinical protection. Post-licensure evaluation of vaccine effectiveness will, therefore, be of increased importance. One vaccine being developed is the serogroup A meningococcal (Men A) conjugate vaccine produced by the Meningitis Vaccine Project (MVP), a partnership between the World Health Organization and the Program for Applied Technology in Health. This vaccine will likely be the first meningococcal conjugate vaccine introduced on a large scale in Africa. This paper summarizes the general steps required for vaccine development, reviews the use of immunogenicity criteria as a licensing strategy for new meningococcal vaccines, and discusses plans for evaluating the impact of a meningococcal A conjugate vaccine in Africa. Impact of this vaccine will be measured during a vaccine-demonstration project that will primarily measure the effectiveness of vaccine. Other studies will include evaluations of safety, vaccine coverage, impact on carriage and herd immunity, and prevention-effectiveness studies.     

Clonal analysis of the serogroup B meningococci causing New Zealand's epidemic

An epidemic of meningococcal disease caused by serogroup B meningococci expressing the P1.7-2,4 PorA protein began in New Zealand in 1991. The PorA type has remained stable. Different porB have been found in association with the P1.7-2,4 PorA, although type 4 has been most common. The clonal origins of B:P1.7-2,4 meningococci isolated from cases during 1990 to the end of 2003 were analysed. In 1990, the year immediately preceding the recognized increase in disease rates, all three subclones (ST-41, ST-42, and ST-154) of the ST-41/44 clonal complex occurred among the five isolates of B:P1.7-2,4. The two sequence types, ST-42 and ST-154, continued to cause most disease throughout New Zealand. Isolates belonging to subclone ST-41 were mostly identified early in the epidemic and in the South Island. 16S rRNA typing indicated that isolates belonging to the subclones ST-41 and ST-154 share a common ancestor, with those typing as ST-42 more distantly related with some genetically ambiguous. It is possible that ST-41 and ST-154 may have evolved one from the other but evolution to ST-42 is more difficult to explain. It is possible that one or more of the ST types could have been introduced into New Zealand prior to the first detection of clinical cases in 1990. Genetic diversity may have occurred during carriage in the community.     

Safety and immunogenicity of New Zealand strain meningococcal serogroup B OMV vaccine in healthy adults: beginning of epidemic control

As the first step towards control of a strain specific epidemic of meningococcal disease in New Zealand (NZ), this study, an observer-blind, randomised controlled trial in 75 healthy adults, evaluated safety and immunogenicity of two different dosages of a meningococcal group B vaccine administered in a three dose regime. The "tailor-made" outer membrane vesicle (OMV) vaccine (candidate vaccine) developed using a New Zealand meningococcal group B strain (B:4:P1.7b,4) was well tolerated with no vaccine related serious adverse events. Similar local and systemic reactions were observed in those receiving the New Zealand candidate vaccine and the control parent Norwegian vaccine (MenBvac). A four-fold rise in serum bactericidal antibodies (SBAb) against the vaccine strain 4-6 weeks after the third vaccination was achieved in 100% of New Zealand candidate vaccine 2,519 microg participants and in 87% of 50 microg participants. The safety and immunogenicity profile observed in this study of healthy adults enabled studies in children to be initiated using 25 microg dosage.     

Control of epidemic group A meningococcal meningitis in Nepal

During the first six months of 1983, an epidemic of serogroup A meningococcal meningitis occurred in the Kathmandu valley of Nepal, resulting in 875 cases and 95 deaths. The annual attack rate was 103 cases per 100,000 population, with a peak attack rate occurring in April. Epidemic meningococcal disease had not been recognized previously in Nepal. Early in 1984, a review of hospital-based data on pyogenic meningitis in Kathmandu showed three times as many cases per month compared with the same period the previous year, suggesting that a recurrent epidemic was unfolding. Beginning in February 1984, a vaccination campaign directed at a high-risk target population of people aged 1-24 years was launched; over 329,000 doses of bivalent A/C meningococcal vaccine were given, achieving approximately 64% coverage of the target population. A dramatic decline in the number of new meningitis cases occurred coincident with the initiation of the mass vaccination campaign. This experience demonstrates that it is possible, with appropriate surveillance efforts, to detect an evolving epidemic of meningococcal disease early in its course and to institute control measures in advance of the expected epidemic peak.     

Epidemiology of bacterial meningitis in Niamey, Niger, 1981-96.

In the African meningitis belt the importance of endemic meningitis is not as well recognized as that of epidemics of meningococcal meningitis that occur from time to time. Using retrospective surveillance, we identified a total of 7078 cases of laboratory-diagnosed bacterial meningitis in Niamey, Niger, from 1981 to 1996. The majority (57.7%) were caused by Neisseria meningitidis, followed by Streptococcus pneumoniae (13.2%) and Haemophilus influenzae b (Hib) (9.5%). The mean annual incidence of bacterial meningitis was 101 per 100,000 population (70 per 100,000 during 11 non-epidemic years) and the average annual mortality rate was 17 deaths per 100,000. Over a 7-year period (including one major epidemic year) for which data were available, S. pneumoniae and Hib together caused more meningitis deaths than N. meningitidis. Meningitis cases were more common among males and occurred mostly during the dry season. Serogroup A caused 85.6% of meningococcal meningitis cases during the period investigated; three-quarters of these occurred among children aged < 15 years, and over 40% among under-5-year-olds. Both incidence and mortality rates were highest among infants aged < 1 year. In this age group, Hib was the leading cause of bacterial meningitis, followed by S. pneumoniae. The predominant cause of meningitis in persons aged 1-40 years was N. meningitidis. Use of the available vaccines against meningitis due to N. meningitidis, S. pneumoniae, and Hib could prevent substantial endemic illness and deaths in sub-Saharan Africa, and potentially prevent recurrent meningococcal epidemics.     

Epidemiology of dengue/dengue hemorrhagic fever in Malaysia--a retrospective epidemiological study. 1973-1987. Part II: Dengue fever (DF).

Dengue fever (DF) has been endemic in Malaysia since 1902 and reached epidemic proportions in 1973. The incidence rate of the disease in 1973 was 5.4 cases per 100,000 and reached 10.4 cases per 100,000 in 1987. The Chinese are the main ethnic community affected showing an overall morbidity rate of 9.0 cases per 100,000 followed by Malays 2.9 cases per 100,000 and Indians 2.4 cases per 100,000. The ethnic race ratio between Chinese, Malays and Indians which was 3.7:1:1.3 in 1975 reached 3.7:1:0.9 in 1987. The attack rates were observed to be higher in the males. The mean male:female ratio among Chinese was 1.1:1, while for Malays and Indians it was 1.5:1. The age-specific morbidity rate was highest in the 10- to 19-year age group followed by the 20- to 29-year age group. Epidemics of dengue fever were found to occur seasonally with the appearance of two peaks, viz. one in June and the other in August. Dengue fever, a rural disease before, has established itself as an urban disease.     

Meningococcal disease in Spain, 1990-1997. Change in its epidemiological pattern

BACKGROUND: In Spain, the presentation of meningococcal disease in the 1980s was closely linked to the predominance of N. Meningitidis serogroup B. This situation changed at the beginning of the 1990s, observing a growing trend of serogroup C strains in the isolation procedures carried out in some areas of the country, together with an increase in the incidence of the disease starting in the 1995-1996 season. The purpose of this study is to characterise the epidemiological pattern of meningococcal disease in Spain during the 1990-97 season and, in particular, where the disease was caused by the phenotype C:2b:P1.2.5 in this period of etiological change. METHODS: Retrospective study of the cases of meningococcal disease in Spain, with the exception of the Autonomous Communities of Andalusia, Cantabria, Madrid, Basque Country and Valencia, between 1990-1997. The epidemiological data were obtained from the Compulsory Disease Reporting system, through individualised notification of cases, and the microbiological data from the Meningococcus Reference Laboratory of the National Microbiology Centre. RESULTS: The incidence of meningococcal disease in the period studied, 1990-1997, was 3.81 x 10 - 6 person-years, increasing by 0.1851 cases per 100,000 inhabitants per year. Starting in 1995, the incidence caused by serogroup C practically tripled with respect to the preceding period, with a rate of incidence in 1997 of 2 cases per 100,000 inhabitants. This increase was to a large extent due to the emergence of the phenotype C:2b:P1.2,5, which in that same year registered an incidence of 1 case per 100,000 inhabitants. The increase in incidence affected all age groups, but was particularly significant in the 5-19 year-old group (annual rate of growth: 13.3%; P < 0.001). It was also found that there was an increase in the number of outbreaks reported and cases associated to them. The overall mortality rate was 7.7% (95% confidence interval: 7.0-8.4), and the mortality associated with the phenotype C:2b:P1.2.5 was significantly higher than that of the serogroup B chosen as reference (odds ratio: 1.69; 95% CI: 1.05-2.71), following adjustment for age, sex, clinical form and year. CONCLUSIONS: The pattern of meningococcal disease in the territory studied, during 1990-1997, was characterised by an increase in the incidence of serogroup C, particularly the emerging phenotype C:2b:P1.2,5. Together with this increase, a displacement of the incidence to higher age groups was observed, together with a tendency towards temporospatial aggregations of cases and an increase in the mortality associated with the new phenotype. This pattern is characteristic of epidemic situations of meningococcal disease caused by serogroup C.     

Detection of meningitis epidemics in Africa: a population-based analysis.

Portions of sub-Saharan Africa are subject to major epidemics of meningococcal meningitis that require early detection and rapid control. We evaluated the usefulness of weekly meningitis rates derived from active surveillance data in Burkina Faso for detecting a meningitis epidemic. By analysing the rates of disease in 40 x 40km2 areas within a study region of Burkina Faso, we found that a threshold of 15 cases/100,000/week averaged over 2 weeks was 72-93% sensitive and 92-100% specific in detecting epidemics exceeding 100 cases/100,000/year. During epidemic periods, the positive predictive value of this threshold approached 100% for detecting local epidemics. Additionally, meningitis incidence was proportional to village size, with villages greater than 8000 having the highest disease rates during a major group A meningococcal epidemic in 1983-1984. Despite the rudimentary nature of surveillance data available in many developing countries, these data can be used to detect the early emergence of meningitis epidemics. Additional studies are needed to determine the relevance of this approach for detecting epidemics.     

Meningococcal disease and social deprivation: a small area geographical study in Gwent,UK

Although meningococcal disease is known to be linked to characteristics of individuals associated with social deprivation, there is only limited evidence of a relation with area-based measures of deprivation. In a small area geographical study, we ascertained 295 confirmed or probable cases occurring between 1996 and 1999 in the socially diverse resident population of Gwent Health Authority, equating to an average annual rate of 13.2 per 100,000. Incidence rates of meningococcal disease increased from 8.1 per 100,000 in the least deprived fifth of enumeration districts to 19.8 per 100,000 in the most deprived fifth, a relative risk of 2.4 (95% CI 1.7-3.6). In Poisson regression, the percentage change in the incidence rate arising from a unit change in the enumeration district Townsend score, was 9.4% (95% CI 6.2-12.6%). Strongest associations were found for the under 5 age group, serogroup B disease and with the overcrowding variable component of the Townsend index. Our study quantifies the strength of the relation between meningococcal disease and social deprivation at small area level and provides further evidence of the need for action to reduce health inequalities.     

四川省1950—1996年细菌性痢疾流行病学分析

四川省１９５０～１９９６年累计发生细菌性痢疾５０４７８２０例，死亡１７８９８例，发病率波动在１２．０１～４５１．１８／１０万之间，平均年发病率为１２４．９４／１０万，经游程检验，４７年间发病率总的升降趋势不具有统计学意义。病死率波动在０．０５～１．９０％之间；７８．２８％的病例发生在７～１０月；发病最高年龄组为０～４岁，发病专率为４９６．４８／１０万，次为２０～２４岁为２６５．６２／１０万，最低是１０～１４岁仅为４５．２６／１０万；山区发病高于平原及丘陵地区；发病农民占４０．１１％，其次是儿童占２６．７４％。对检出的１０１６９株志贺氏菌菌群分析，Ａ群占３．２％，Ｂ群占８１．３％、Ｃ群占１．７％、Ｄ群占１３．８％，在Ｂ群中，以２ａ血清型占２２％，３血清型占１０％，１ｂ血清型占８％，而福氏３型由５０年代的３４．１％逐年代降至现今的１０％。对流行因素及防治策略作了初步分析和探讨，于今后预防和控制菌痢的发生和流行有参考意义。     

MeNZB: a safe and highly immunogenic tailor-made vaccine against the New Zealand Neisseria meningitidis serogroup B disease epidemic strain

Clinical studies have been conducted in New Zealand evaluating the safety and immunogenicity of an outer membrane vesicle (OMV) vaccine, MeNZB, developed to control epidemic disease caused by group B meningococci, subtype P1.7b,4. MeNZB, administered in a three-dose regimen, was well tolerated and induced a seroresponse, defined as a four-fold rise (> or =titre 8) in serum bactericidal antibodies against the vaccine strain 4-6 weeks after the third vaccination, in 96% (95% confidence interval (CI): 79-100%) of adults, 76% (95% CI: 72-80%) of children, 75% (95% CI: 69-80%) of toddlers and 74% (95% CI: 67-80%) of infants receiving MeNZB. In conclusion, these findings suggest that MeNZB is safe and is likely to confer protection against systemic group B meningococcal disease caused by the epidemic strain.     

Carriage of a new epidemic strain of Neisseria meningitidis and its relationship with the incidence of meningococcal disease in Galicia, Spain

In Galicia, Spain, a dramatic increase in the incidence of meningococcal disease was seen in the 1995-6. The annual incidence rose to 11 per 10(5) inhabitants, and 80% of identified strains were C:2b:P1.2,5. This led to the implementation of an intensive A+C vaccination campaign for the population aged 18 months to 19 years. During this campaign the prevalence of carriage in areas with high and low incidence was studied. Nasopharyngeal swabs were taken from 9796 subjects immediately before the administration of meningococcal vaccine, plated onto Thayer-Martin plates, incubated and sent for analysis to the Reference Laboratory for Neisseria in Spain. The prevalence of the C:2b: P1.2,5 strains was 0.6% (95% CI 0.29-0.88) in the high incidence area, and 0.41% (95 % CI 0.00-1.04) in the low incidence area, and that of serogroup C (all strains) 1.36% (95% CI 0.80-1.80) and 0.89% (95% CI 0.09-1.69) respectively. The prevalence of N. meningitidis (all strains) was almost the same in both areas (8%). Carriers of the epidemic strain were not found in the 2-4 year age group, that most affected by the disease. Our data showed a wide distribution but a low carriage rate of the epidemic strain C:2b:P1.2,5 in the high and low disease incidence areas studied; the difference in the carriage rates between the two areas was not statistically significant.     

Serotype-specific outbreak of group B meningococcal disease in Iquique, Chile

From 1979 to August 1987, there have been 178 cases of meningococcal disease in Iquique, Chile, a city of about 140,000. The attack rate for the last 5 years has been in excess of 20/100,000 per year, more than 20 times greater than for the country overall. The mortality rate was 6%. The disease occurred in patients with ages from 4 months to 60 years, but 89% of cases were in patients less than 21 years. The largest number of cases were in the age group 5-9 years (n = 54), but the highest incidence occurred in children less than 1 year of age (72.8/100,000 per year). The male/female ratio was 1.2. Cases occurred all year round with little seasonal variation. Of the 178 cases, 173 were biologically confirmed. Serogroup analysis of strains from 135 patients revealed A = 1, B = 124, C = 10. Forty-four group B strains from 1985-7 were serotyped: 15:P1.3 = 36, 15:NT = 4, 4:P1.3 = 2, NT:NT = 2. Ten of 11 of the outbreak strains tested were sulfadiazine-resistant. This is the first recognized outbreak caused by a Gp B:15 strain in South America. It shares many of the characteristics of outbreaks caused by closely related strains in Europe, such as a predilection for older children and adolescents, sulfadiazine-resistance, and sustained high attack rates. The Iquique strain (B:15:P1.3) belongs to the same genetic clone (ET-5 complex) as the Norway (B:15:P1.16) and the Cuban (B:4:P1.15) strains.     

MLEE and PFGE characterization of Neisseria meningitidis serogroup C and B isolated in the Slovak Republic in 1998

In the Slovak Republic the incidence and mortality of invasive meningococcal disease increased after 1995 when the new meningococcal clone of Neisseria meningitidis C:2a:P1.2,P1.5, ET-1.5/37 emerged. The new clone spread between 1995 and 1998 throughout the whole country. Morbidity of invasive meningococcal disease was 1.6/100,000 of the population and fatality reached the highest level of 23% in the Slovak Republic in 1998. The new clone caused a new emergent epidemiological and clinical situation. The occurrence of invasive meningococcal disease caused by this clone has continually risen since 1995. In 1998 72% of all diseases in Slovakia were caused by serogroup C. The emerging clone C:2a:Pl.2,P1.5 represented 74% of the serogroup C isolates. Clonality and genetic diversity of 15 selected meningococcal strains causing invasive meningococcal disease was compared by multilocus enzyme electrophoresis (MLEE) and DNA macrorestriction analysis by pulsed-field gel electrophoresis (PFGE). The strains of serogroup C and B were isolated in all regions of Slovakia in 1998. The majority of isolates belong to hypervirulent clone ET-15 as determined by MLEE. By PFGE a higher degree of diversity was observed.     

Epidemiology of epidemic diphtheria in three regions, Russia, 1994–1996

Background: A massive diphtheria epidemic which began in the former Soviet Union in 1990 is the first large-scale diphtheria epidemic in developed countries in more than 30 years and has primarily affected adults. In response, health authorities attempted to maximize vaccination for children and conducted an unprecedented campaign to vaccinate adults. Methods: We analyzed diphtheria surveillance data (case report forms and diphtheria vaccine coverage data) from three Russian regions from January 1994 to December 1996 and estimated vaccine effectiveness by the screening method. Results: We reviewed records from 2243 (97.2%) of 2307 reported cases. The highest cumulative incidence in the period was among children aged 5 to 9 years (106 cases per 100,000 population); adults aged 40–49 years had the highest adult incidence for disease (88 cases per 100,000) and the highest incidence of any age group of clinically severe disease (29 cases per 100,000) and death (5.1 deaths per 100,000). The incidence among women aged 20–49 years (82 per 100,000 women) was higher than among men (47 per 100,000, p<0.01). The annual incidence decreased from 25.2 cases per 100,000 population in 1994 to 9.4 cases per 100,000 in 1996. The decrease occurred as adult coverage increased from an estimated 25–30% in December 1992 to 88% in December 1995. Vaccine effectiveness was high among both children and adults. Conclusions: The Russian diphtheria epidemic primarily affected adults, especially women; this pattern is likely representative of diphtheria epidemics in immunized populations. Raising childhood immunization coverage and mass adult vaccination was effective in controlling the Russian epidemic. An improved understanding of the current epidemiology of diphtheria will be useful to design public health responses to prevent or control modern epidemics.     

Hospital-based surveillance of meningococcal meningitis in Salvador, Brazil

This study aimed to describe the clinical, epidemiological and microbiological features of meningococcal meningitis in Salvador, Brazil. Between February 1996 and January 2001, a hospital-based surveillance prospectively identified cases of culture-positive meningococcal meningitis. Demographic and clinical data were collected through interview and medical chart review. Antisera and monoclonal antibodies were used to determine the serogroup and serotype:serosubtype of the isolates, respectively. Surveillance identified a total of 408 cases of meningococcal meningitis, with a case fatality rate of 8% (32/397). The mean annual incidence for the 304 culture-positive cases residing in metropolitan Salvador was 1.71 cases per 100,000 population. Infants <1 year old presented the highest incidence (14.7 cases per 100,000 population). Of the 377 serogrouped isolates, 82%, 16%, 2% and 0.3% were serogroups B, C, W135 and Y, respectively. A single serotype:serosubtype (4,7:P1.19,15) accounted for 64% of all cases. Continued surveillance is necessary to characterise strains and to define future prevention and control strategies.     

Early detection and response to meningococcal disease epidemics in sub-Saharan Africa: appraisal of the WHO strategy

OBJECTIVE: To assess the sensitivity, specificity and predictive value positive of the WHO threshold strategy for detecting meningococcal disease epidemics in sub-Saharan Africa and to estimate the impact of the strategy on an epidemic at district level. METHODS: Data on meningitis cases at the district level were collected weekly from health ministries, WHO country and regional offices, and nongovernmental organizations in countries where there were epidemics of meningococcal disease in 1997. An epidemic was defined as a cumulative district attack rate of at least 100 cases per 100,000 population from January to May, the period of epidemic risk. The sensitivity, specificity and predictive value positive of the WHO threshold rate were calculated, and curves of sensitivity against (1 - specificity) were compared with alternatively defined threshold rates and epidemic sizes. The impact of the WHO strategy on a district epidemic was estimated by comparing the numbers of epidemic cases with cases estimated to have been prevented by vaccination. FINDINGS: An analysis was made of 48 198 cases reported in 174 districts in Benin, Burkina Faso, the Gambia, Ghana, Mali, Niger, and Togo. These cases were 80.3% of those reported from Africa to WHO during the 1997 epidemic period. District populations ranged from 10,298 to 573,908. The threshold rate was crossed during two consecutive weeks in 69 districts (39.7%) and there were epidemics in 66 districts (37.9%). Overall, the sensitivity of the threshold rate for predicting epidemics was 97%, the specificity was 95%, and the predictive value positive was 93%. Taken together, these values were equivalent or better than the sensitivity, specificity and predictive value positive of alternatively defined threshold rates and epidemics, and remained high regardless of district size. The estimated number of potential epidemic cases decreased by nearly 60% in the age group targeted for vaccination in one district where the guidelines were followed in a timely manner. CONCLUSION: The use of the WHO strategy was sensitive and specific for the early detection of meningococcal disease epidemics in countries of sub-Saharan Africa during 1997 and had a substantial impact on a district epidemic. Nevertheless, the burden of meningococcal disease in these countries remains formidable and additional control measures are needed.     

Impact of systematic vaccination with the antimeningococcal C conjugated vaccine in a health area in Andalusia

BACKGROUND: A retrospective longitudinal study of population incidence was made to assess the effectiveness of meningococcal serogroup C conjugate vaccine, after its mass introduction in children in the geographic area of a health district, measuring its population impact, and we have studied the state of the meningococcal disease. METHODS: Vaccine coverage in children born between 1991 and 2001, and rates of incidence in declared cases of meningococcal disease in seven epidemiological seasons (1997/98 to 2003/04) were calculated. The impact of vaccination against serogroup C meningitis was assessed comparing the average annual rates of previous and later seasons to the vaccination campaigns in population younger and older than 10, using the Fisher exact test. RESULTS: In all the study period, 109 cases of meningococcal disease were declared, of which 50 were of serogroup C meningococcal disease. Starting from 2000/2001 season the incidence of serogroup C disease decreased in the population below 10. In this age group, the annual average rate of post-vaccine seasons decreases in respect to pre-vaccine (from 8.2 to 2.0 per 100,000 inhabitants) showing a statistically significant difference. In the population above 10 years, this incidence reduction was not observed. In the study period, no case of vaccine failure was declared. CONCLUSIONS: The absence of vaccine failure and the impact observed on the incidence of serogroup C meningococcal disease in children under 10 suggests the effectiveness of this new conjugate vaccine, together with suitable vaccination conditions (vaccination schedule, high catch-up, etc.) which are developing in our health district.