Editorial Commentary: Disparities in Invasive Pneumococcal Disease Rates Between Populations: Will the Extended Pneumococcal Conjugate Vaccines Be a Game-Changer?

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The first 7-valent pneumococcal conjugated vaccine (PCV7) was developed on the basis of data demonstrating that within the United States and other developed countries, the 7 vaccine serotypes were responsible for >80% of invasive pneumococcal disease (IPD) in young children [1]. Indeed, shortly after the introduction of PCV7, a significant and dramatic reduction in IPD rates was observed in many countries that had introduced the vaccine [2–5].However, several factors led to the development of extended, highervalency pneumococcal conjugate vaccines (PCVs). These factors included epidemiological data from different parts of the world, mainly from developing countries, demonstrating increase in IPD caused by serotypes not covered by PCV7, such as 1, 5, and 7F, as well as worldwide increase in disease caused by the virulent, highly antibiotic-resistant serotype 19A [6]. Disparities in IPD rates among populations with different socioeconomic status have been previously reported, emphasizing overcrowding, poverty, malnutrition, low vaccine uptake, and underlying diseases as major factors contributing to high pneumococcal disease rates [4, 7, 8] Wortham and colleagues, in this issue of Clinical Infectious Diseases, present the results of a multicenter study evaluating the secular trends in IPD rates, and have focused on racial disparities in invasive Streptococcus pneumoniae infections between 1998 and 2009, before and after the introduction of PCV7 to the national immunization program in the United States. The aim of their study was to compare IPD rates in different populations, and mainly to compare rates between black and white populations within the United States. These study results are noteworthy for several reasons. First, the reduction in PCV7 serotype IPD is very impressive, especially given the large database, describing IPD incidences in different age groups and different racial populations in a population of >29 million people with >47 000 IPD cases over a 10-year period. Second, the effect of total reduction in IPD rates was accompanied by closure of the disparity gaps in PCV7-type IPD rates between 2 different racial populations— blacks and whites. This effect of diminished disparity in IPD rates between the 2 populations was to be expected, as was described in several earlier reports, where PCV7 introduction resulted in decreased PCV7-type IPD rates (close to elimination in most cases) in various populations, including populations with different rates, residing in the same country [4]. This is yet another demonstration of the PCV7 impact, overcoming any other confounding factors contributing to IPD rates, such as poverty and ethnicity. Third, the rates of non-PCV7 serotype IPD were higher in the black population than in the white population, in the prePCV7 era. As an increase in non-PCV7 serotypes disease was observed in both populations, it has led to a sustained gap in the nonvaccine-type disease between them. This can be partially attributed to other background factors differentiating between the 2 populations that remained unchanged. Fourth, themajority of IPD in 2009 was attributed to additional 13-valent pneumococcal conjugated vaccine (PCV13) serotypes not included in PCV7 (1, 3, 5, 7F, and 19A). New data from countries that have introduced PCV13 suggest that PCV13 did significantly reduce Received 9 February 2014; accepted 10 February 2014; electronically published 27 February 2014. Correspondence: David Greenberg, MD, Pediatric Infectious Disease Unit, Soroka University Medical Center, Beer-Sheva, Israel (dudi@bgu.ac.il). Clinical Infectious Diseases 2014;58(9):1258–9 © The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals. permissions@oup.com. DOI: 10.1093/cid/ciu113