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Vaccination: paying it forward

Following 15-year evolution of pneumococci, vaccine and antibiotic use in Portuguese children

Oeiras, 29.04.2016

Researchers from the Laboratories of Raquel Sá-Leão and Hermínia de Lencastre found that widespread use of the vaccine against Streptococcus pneumoniae has led to a significant decline of the bacteria serotypes included in the vaccine in Portuguese children under 6 years of age, in a study now published. The researchers also found a decrease in antimicrobial consumption, although it may be too early to expect generalized changes in antimicrobial resistance rates.

Streptococcus pneumoniae (the pneumococcus) is a bacterial pathogen that often colonizes asymptomatically the nasopharynx of young children. However, the pneumococcus can cross biological barriers and cause several diseases such as otitis media, pneumonia, bacteremia and meningitis. Children attending day-care centers are considered to be the major reservoirs of pneumococci and cross-transmission in these settings can be extremely high.

There are numerous variants of pneumococcus, including 95 different serotypes although only a few of these are responsible for the majority of disease. In 2000, the first vaccine against pneumococcus became available in the USA, targeting 7 of the most harmful serotypes of S. pneumoniae. Later versions were developed against 10 and 13 serotypes that are now being used. In Portugal the vaccine became available commercially in 2001 and was recommended by pediatricians, but it was not introduced in the Portuguese National Immunization Plan until 2015.

ITQB NOVA researchers have studied pneumococcal serotype distribution and antimicrobial resistance rates in children in 2009 and 2010, when vaccine coverage in their study population had been sustained at 75–80% for nearly 5 years. They were able to compare the results with similar data that have been obtained by Herminia de Lencastre Lab since 1996. Together, the data represent a unique comparable 15-year-long series of surveillance of pneumococcal carriage, covering the pre- and pos-vaccination-era, allowing the study of the impact of pneumococcal vaccination, antimicrobial use, and secular trends as drivers of change in the pneumococcal population that occurred over time.

Pneumococcal colonization is a prerequisite for disease and transmission and this has been the subject of some of our studies”,  explained Raquel Sá-Leão, who coordinated the current research. “The long data set we have been collecting enabled us to establish a solid baseline prior to introduction of the vaccine. This was essential to distinguish the contribution of the vaccine compared to natural temporal trends. The results indicate that the vaccine has had a sustained impact on the pneumococcal population by preventing colonization with vaccine serotypes. Ongoing studies at ITQB are aiming to evaluate the impact of novel expanded conjugate vaccines in public health.”

Antimicrobial resistance remains a concern even in the era of vaccination suggesting that additional efforts to contain antimicrobial use must be implemented, and surveillance of pneumococcus carriage in day-care centers needs to be continued.



Original article

Vaccine 34 (2016) 1648–1656

The impact of private use of PCV7 in 2009 and 2010 on serotypes and antimicrobial resistance of Streptococcus pneumoniae carried by young children in Portugal: Comparison with data obtained since 1996 generating a 15-year study prior to PCV13 introduction

Sónia Nunes, Sofia Félix, Carina Valente, Alexandra S. Simões, Débora A. Tavares, Sónia T. Almeida, Ana C. Paulo, António Brito-Avô, Hermínia de Lencastre, Raquel Sá-Leão.


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