The threat of invasive pneumococcal disease

In a recent study, the evolution of pneumococcal disease caused by serotype 3 in Spain in the last three decades (1989-2020) has been analyzed. Among its main conclusions, it stands out that childhood vaccination has not had the expected impact of group protection in pneumococcal disease caused by serotype 3 in adults, so this population group needs direct protection by vaccination.

The study was carried out by a team including, among others, Carme Ardanuy and Sara Calvo-Silveria, both from the Bellvitge University Hospital (HUB) in Hospitalet de Llobregat, Barcelona, ​​and the Bellvitge Biomedical Research Institute (IDIBELL). , which is one of the institutions CLOSE to the Generalitat of Catalonia.

Streptococcus pneumoniae, pneumococcus, is an opportunistic pathogen that colonizes the respiratory tract and can cause serious infections such as meningitis or pneumonia. In fact, S. pneumoniae continues to be the leading cause of mortality in respiratory diseases worldwide. Currently, more than 100 different genetic variations known as serotypes have been described, although there are differences in the invasive capacity and associated mortality between them. Invasive pneumococcal disease caused by serotype 3 pneumococci is associated with high mortality and, although the 13-valent conjugate vaccine (PCV13) includes this serotype, its incidence remains high.

The research team also performed a whole genome sequencing study, revealing that serotype 3 pneumococci have two main lineages, and that one of them, the CC180-GPSC12 lineage, has been increasing in frequency over the years. Although both lineages were genetically homogeneous, CC180-GPSC12 presented greater genetic diversity with more presence of prophages and mobile genetic elements. “Some of these elements confer resistance to antibiotics, which is worrying,” says Dr. Ardanuy.

Clinical data and trends

Thus, pneumonia was the main form of presentation of the disease, and more than half of the patients also had some comorbidity, diabetes mellitus being the most common. Mortality at 30 days was high, although a decrease was observed throughout the study period from 32.4% to 16.7. No significant differences were observed in terms of the clinical characteristics of the patients and the mortality of cases caused by both lineages.

Furthermore, the study revealed that the overall incidence of invasive pneumococcal disease decreased from 21.0 to 12.9 cases per 100,000 inhabitants between the periods before and after the introduction of the PCV13 vaccine, demonstrating group protection. This is because colonization by pneumococcus (asymptomatic carrier) is more common in children, and vaccination reduces the concentration of pneumococci of the serotypes included in the vaccine, so there is less transmission. However, the specific incidence of invasive pneumococcal disease caused by serotype 3, included in PCV13, remained stable so that the indirect protection of childhood vaccination had no impact on invasive pneumococcal disease caused by this particular serotype in the adult.

The recent introduction of new (more effective) conjugate vaccines for the vaccination of the adult population will be an important tool in the control of pneumococcal diseases in adults. “It is necessary to increase vaccination rates against pneumococcus in adults to have good direct protection in risk groups such as those over 65 years of age, immunosuppressed, or patients with comorbidities to achieve the same effectiveness that has already been demonstrated in children” concludes Dr. Ardanuy.

Members of the research team. (Photo: IDIBELL)

This study, carried out within the framework of the Pneumonia Program of the Red Biomedical Research Center for Respiratory Diseases (CIBERES) in Spain, has the collaboration of research staff from the Gregorio Marañón hospitals (in Madrid), Donostia (in the Basque Country ), Vall d’Hebron, Parc Taulí, Germans Trias i Pujol and Bellvitge (in Catalonia), as well as the Pneumococcus Reference Laboratory, the Carlos III Health Institute, the Barcelona Supercomputing Center and the Red de Biomedical Research Center. Infectious Diseases (CIBERINFEC), in Spain.

The study is titled “Evolution of invasive pneumococcal disease by serotype 3 in adults: a Spanish three-decade retrospective study.” And it has been published in the academic journal The Lancet Regional Health. (Source: IDIBELL)