Introducing a vaccine against the 13 most dangerous types of pneumococcal bacteria may raise concerns that other pneumococcal bacteria not covered by the vaccine may become dangerous. This does not seem to be the case in France.
A 7-year study of pneumococcal vaccination of children in France shows that the introduction of the vaccine directed against the 13 most dangerous serotypes of pneumococci is associated with the emergence of other pneumococci not covered by the vaccine, but that those These are not dangerous: they do not cause serious infections (“invasive infections” such as pneumonia, sepsis, meningitis). This study appeared in the JAMA Pediatrics.
A study on pneumonia
Faced with the emergence of strains of pneumococci other than those covered by a vaccination when it was introduced, the question arises of the possible responsibility of these other strains (serotypes) in serious pneumococcal infections (pneumonia, septicemia, meningitis).
The study involved 12,587 children with pneumonia, including 4,273 requiring hospitalization. The introduction of the 13-valent pneumococcal vaccine was followed by an impressive decrease in the frequency of childhood pneumonia (from 6.3 pneumonia per 1000 emergency room visits before 2014, to 3.8 pneumonia per 1000 emergency room visits in 2017). If there is indeed emergence of new serotypes of pneumococci not covered by vaccination, these do not seem to be the cause of severe pneumonia.
Danger of pneumococcal pneumonia
Pneumococcal pneumonia is a major cause of illness and death in children. In children, this is one of the reasons that led to the extension of compulsory pneumococcal vaccination. This vaccination is carried out using a conjugate vaccine which is now directed against 13 species of pneumococci (13 serotypes) because it is these serotypes that are associated with the most serious infections.
A protean bacterium
The pneumococcus (Streptococcus pneumoniae) is a bacterium which has a capsule, composed of complex sugars (polysaccharides) which partly explains its virulence.
Depending on the nature of these polyosides, there is a great diversity of pneumococci, called “serotypes”: about a hundred have thus been described but only a few are currently responsible for “invasive pneumococcal infections”, the most dangerous infections (pneumonia, sepsis, meningitis).
An effective 13-valent vaccine
The vaccine is effective because it is conjugated to a protein that increases its potency (antigenicity) and it protects well against infections due to the 13 serotypes included in the vaccine. However, the previous vaccine was directed against only 7 serotypes and an increase in the frequency of infections due to certain serotypes not covered in the seven-valent conjugate vaccine which contained 7 serotypes (4, 6B, 9V, 14, 18C, 19F and 23F). Since 2010, in France, the conjugate vaccine contains six complementary valences: 1, 3, 5, 6A, 7F and 19A. All these serotypes are responsible for the majority of invasive pneumococcal infections, including pneumonia.
It was therefore interesting to check whether this vaccination limited to 13 serotypes did not reproduce the same phenomenon by causing other potentially dangerous pneumococci to emerge. The 13-valent vaccine is a conjugate vaccine. Conjugation of pneumococcal polysaccharide antigens to protein improves the efficacy of pneumococcal immunization.
This 13-valent conjugate vaccine therefore confers protection against pneumococcal infections, and in particular pneumonia in children. It is also active against the chronic carriage of this bacterium in the upper airways and it can be used from the age of two months. Although it seems to be responsible for the increase in importance of the other pneumococcal serotypes not covered by the vaccine, the latter do not appear to be associated with an increase in pneumonia in children.