Meningococcal B (Neisseria meningitidis serogroup B) is a bacterium that causes rare but very serious infections, such as meningitis and sepsis (blood infection). The mortality of these infections is approximately 10% and the risk of permanent sequelae is 20-30% among survivors. Although they can occur at any age, most cases occur in the pediatric age group. The highest incidence and lethality is in healthy children under 3 years of age, followed by adolescents. An immunopreventive vaccine against this germ is currently available.
Situation of meningitis and sepsis in Spain
In Spain, the main cause of invasive meningococcal disease (meningitis and sepsis) is meningococcal B. Its incidence is 0.7 per 100,000 persons/year, slightly higher than the European average. Another germ that used to be common is meningococcus C, which fortunately is under control thanks to vaccination.
Meningitis or sepsis due to meningococcus B can be treated with antibiotics, but sometimes its progression is so rapid that treatment is not effective. In addition to high mortality, associated sequelae include hearing loss, hydrocephalus, neurological disorders, neurodevelopmental problems, amputations, skin complications and kidney failure. For this reason, it is important to prevent infection through vaccination, as recommended by the Spanish Association of Pediatrics.
Meningococcal B vaccine
This is a four-component vaccine (4CMenB) designed using a novel technique called “reverse vaccinology”. Clinical trials have shown that the vaccine is immunogenic and safe in the pediatric age group, and that it induces immunological memory. A study carried out with meningococcal B strains from several European countries, including Spain, has predicted that 73-87% (percentage of potential effectiveness) would be covered by this vaccine. It is expected to have more information on the duration of immunogenicity, which, as has happened with vaccination against meningococcus C, could condition future changes in the recommended immunization guidelines.
Care of the meningitis and sepsis vaccine
The vaccine should be kept in a refrigerator at a temperature between +2ºC and +8ºC, and should not be frozen. It should be injected intramuscularly, with a dose of 0.5 ml. In children under 2 years of age, in the thigh, and from 2 years of age onwards in the shoulder. The number of doses to be administered depends on the age at which vaccination is started. It is recommended to start at 2 months of age. A possible vaccination schedule for those starting at that age (4 doses) is at 3, 5, 7 months and 15 months of age.
The safety of the vaccine has been analyzed in clinical trials. In children less than 24 months of age, the most commonly observed local and systemic adverse reactions have been found to be pain and erythema at the injection site, fever and irritability. Fever occurs more frequently when the vaccine is co-administered with routine vaccines (61%) than when it is administered alone (38%). It is usually low, appears in the first 6 hours and rarely lasts more than 36-48 h. The prophylactic use of paracetamol reduces the probability of fever, as well as other local and systemic adverse effects, without affecting the immune response to the vaccine.
The vaccine is contraindicated if a severe allergic reaction has been experienced with a previous dose or from a vaccine component.