Prevention and control of infectious diseases, especially among children and adolescents, has been a big concern for the Public Health Ministry (PHM) in Cuba. Hitherto vaccines are the most promising prospect for the prevention of community acquired BM. Therefore widespread use of effective vaccines may induce a major impact in preventing the disease, especially when they are used during a long period of time as a part of the NIP, as occurred in Cuba, where a decreasing trend of BM has been documented after vaccination against meningococcus serogroup B and C, and more recently, Hib [4, 9, 10, 12].
Cuban strategy to prevent these infections has been an initial vaccination campaign continued through the NIP.
The first intervention was carried out in 1979 with an A+C vaccine (Pasteur-Merieux) during the meningococcal disease epidemic caused mainly by serogroup C (50,0%) and B (34,3%). The target population was 3, 245 046 individuals from 3 months of age to 19 years old, considered at high risk of disease, achieving 78.2% vaccination coverage. This intervention decreased significantly the serogroup C (7.2%) in 1980, but was ineffective against serogroup B, therefore the incidence continued to rise, but having serogroup B as a predominant causal agent (78.4%) [4, 12].
By the end of 1988, after having being evaluated in a double-blind, placebo-controlled trial, the Cuban anti-meningococcal BC vaccine (VA-MENGOC B-C®) was first administered to high risk age groups and subsequently to all the population from 3 months of age to 24 years of age (an estimated 2 million people or more) [4, 9]. Since 1991 this vaccine has been included in the NIP for children of 3 months of life (2 doses, 2 months apart), decreasing the nation-wide incidence of meningococcal meningitis to below 1 per 100 000 population. For that reason, the contribution of meningococcal meningitis to the overall incidence of BM in Cuba is very small at present .
During this period, serogroup B Neisseria meningitidis (classified by a commercial sera Wellcome Diagnostic, England) has been the only one isolated bacteria and subsequently confirmed by the Neisseria Laboratory at the IPK, where the strain B4. P1. 19.15 has been the most frequently identified, using ELISA . It is likely due to the fact that VA-MEMGOC B-C prevents the disease, but does not eliminate the nasopharyngeal carriage .
Shifts in the frequency and circulation of each bacteria and/or strain into a region, country or continent depends on the interaction of both the pathogen and the host within settled environmental conditions, nevertheless important changes may be induced by prolonged and massive vaccination programmes.
Small children are widely considered a high-risk group for BM, as it was confirmed in our study, where the highest incidence was observed in less than 6 year olds. [15, 16]. In Cuba Hib and Spn were the leading pathogens of BM in this group since 1993, as a result of previous nationwide vaccination against meningococcus [5, 12].
Due to the increase of infant mortality caused by Hib infections, the PHM decided to start using an available conjugate vaccine against Hib in 1999. The vaccine was initially used in a campaign for small children and continued through the NIP . The incidence of Hib meningitis dropped by 47% after initial vaccination, especially in small children, coinciding with reports in other countries where those vaccines had also been used. Another beneficial effect of conjugated Hib vaccine is the elimination of carriage among vaccinated populations [17–19].
For these reasons, we considered that the vaccination against Hib contributed decisively to the overall decrease of BM in small children described above, and undoubtedly the development of such vaccines has been one of the most important events in the history of the prevention and control of infectious diseases in paediatrics [1, 20].
Spn is not a common cause of meningitis epidemics and outbreaks . We considered that the steady low incidence of meningococcal meningitis as well as the drastic and significant reduction of Hib meningitis in small children achieved during 1999 in Cuba, may have contributed to an increase of pneumococcal meningitis in 1999 and 2000, especially in children under 6 years old. We hypothesised that Spn might have filled somehow the ecological niche laid down abruptly by Hib after the incidence decrease subsequent to vaccination. Since then Spn is the leading cause of BM in Cuba as also occurs in many regions of the world .
The improvement of the BM surveillance system in Cuba increases substantially quantitative and qualitative information about this group of infections . Despite these achievements, an important number of cases still remains of unknown aetiology due to previous antibiotic therapy.
Regarding the gender, we observed in our study that infections in male predominated those in females, contrarily to other author that point out non significant differences between males and females .
CFR depends on, among other factors, the host response, the virulence of the pathogen and the quality and timeliness of medical attention. Average CFR was nearly 10% and similar figures are reported in many developed countries, where it could be as low as 2% and as high as 25% [23, 24], though in developing countries it may be higher. Pneumococcus was the most lethal germ, with CFR nearly 25%, and similar figures are reported in other regions of the world [16, 25, 26].
Two well-defined seasons are recognised in Cuba: the rainy (April to September) and the dry (October to March). The monthly average case distribution of Hib and pneumococcal meningitis, did not show seasonality differences, but meningococcal meningitis did, increasing the number of cases mainly in September, October and March, coinciding with reports of the literature . In Cuba, September and October is the transitional period of the rainy season to the dry, but also it is the end of the summer vacations and the start of the school year, when many children and adolescents share the same environment (DCC and schools) and are in close contact with one another. Coincidence of these climatic, environmental and socio-cultural conditions, undoubtedly may contribute to the seasonal increase of meningococcal meningitis in our country.
Airborne transmission of infections can be favoured by some environmental conditions such as attendance at boarding institutions, overcrowding areas, poor ventilation and intimate contact [3, 15, 27].
In our study we observed that the overall percentage of cases sleeping in overcrowded dormitories was 15%, but in adolescents reached nearly 30%. It should be considered as an important risk for the transmission of BM in this group, and must call the attention of both, MINED and PHM, for the avoidance of these conditions, where possible, especially in DCC and boarding school.
On the other hand, as a nation-wide improvement of the Cuban educational system during the seventies, a huge number of boarding school (Colleges, Technical and Professional Education) were built nationwide. In these institutions the intimate contact and promiscuity among boarding students may increase airborne infections [3, 15, 27–29]. Nevertheless no strong association of BM with attendance to boarding school or DCC was observed, reinforcing the criteria of the beneficial effect of massive and systematic vaccination against two of the main BM causal pathogens.