Scientists describe how vaccination has affected bacterial variants that cause pneumonia

  • Vaccines have significantly reduced pneumococcal pneumonia.
  • A research by IDIBELL and the Bellvitge University Hospital has described how vaccines have changed the distribution of the different pneumococcal serotypes.
  • Studying the evolution of pneumonia epidemiology allows the design of more effective vaccination strategies.
NO118 - C Ardanuy_Microorg - Imatge

Pneumococcus, or Streptococcus pneumoniae, is the main cause of serious infections such as pneumonia or meningitis, as well as less severe ones such as otitis media. Vaccines to prevent infection by these bacteria have completely changed the epidemiology of such diseases, significantly reducing the invasive diseases caused by pneumococcus.

Now, a study by the research group on Epidemiology of Bacterial Infections at IDIBELL and the Bellvitge University Hospital, led by Dr. Carmen Ardanuy, also a researcher at CIBERes, has described the changes in the frequency of variants or serotypes and antibiotic sensitivity of pneumococcus that cause pneumonia in adults in Spain between 2011 and 2019. The objective was to describe the impact of vaccination on these variables.

The study published in the journal Microorganisms describes that serotype 3, included in the current vaccine, is the most common in pneumococcal pneumonia. These data are consistent with other previous published studies that indicated that the vaccine had a low effectiveness in preventing infection by this serotype.

The second most frequently found serotype was serotype 8, not included in the current vaccine, and especially associated with bacteremic pneumonia, that is, when the infection spreads from the lungs and reaches the blood. This serotype is notably important in adults under 65 years old. This emphasizes the high invasiveness of this serotype and the importance of including serotype 8 in prevention strategies to try to reduce its prevalence.

Regarding non-bacteremic pneumonia, so, when bacteria do not reach the blood, a high proportion of serotype 11A has been found. This serotype is resistant to beta-lactams antibiotics, such as penicillin, so it is crucial to detect them in order to administer the appropriate treatment. Like serotype 8, serotype 11A will be included in the future vaccine, which might help reduce its incidence.

“The changes observed in this study highlight the need for continuous surveillance of pneumococcal diseases’ epidemiology despite advances in vaccination strategies,” says Dr. Ardanuy. “Studying how the bacteria is evolving can help us propose new, more effective vaccines”.

This research has been possible thanks to the collaboration with members from the Infectious Diseases Service of the Bellvitge University Hospital, the National Microbiology Center (CNM-Madrid) and two CIBERes groups.


The Bellvitge Biomedical Research Institute (IDIBELL) is a biomedical research center created in 2004. It is participated by the Bellvitge University Hospital and the Viladecans Hospital of the Catalan Institute of Health, the Catalan Institute of Oncology, the University of Barcelona and the City Council of L’Hospitalet de Llobregat.

IDIBELL is a member of the Campus of International Excellence of the University of Barcelona HUBc and is part of the CERCA institution of the Generalitat de Catalunya. In 2009 it became one of the first five Spanish research centers accredited as a health research institute by the Carlos III Health Institute. In addition, it is part of the “HR Excellence in Research” program of the European Union and is a member of EATRIS and REGIC. Since 2018, IDIBELL has been an Accredited Center of the AECC Scientific Foundation (FCAECC).

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