Current status and future directions of invasive pneumococcal diseases and prophylactic approaches to control them

Abstract

Streptococcus pneumoniae is a major human bacterial pathogen responsible for millions of deaths each year and significantly more illnesses worldwide. With over 90 different serotypes, providing effective vaccine programs has been a continuing challenge. Since 1983, the world has been introduced to four different pneumococcal vaccines (PPSV23, PCV7, PCV10, and PCV13) each with their own complications and successes. Since vaccination programs began, a decrease in the overall rate of pneumococcal pneumonia and associated diseases has been observed, notably in higher risk populations. However, with a decrease in incidence of vaccine type pneumococcal serotypes, increases in non-vaccine serotypes of the bacteria have been observed along with serotype switching. Additionally, a rise in antibiotic resistant strains of S. pneumoniae is noted. Here we discuss both the positive and negative clinical manifestations of pneumonia vaccine programs and discuss the challenges in pneumococcal vaccine design.

Keywords: Streptococcus pneumoniae; capsular polysaccharide; conjugate vaccines; pneumonia; serotype; serotype replacement.

Figure 1.

Trends in overall rate of IPD (invasive pneumonia disease) in different age groups between the years 1998–2016 in the United States. Blue line represents children under five, orange line adults ages 19–64, gray line adults over the age of 65. Important dates for vaccine introduction and recommendations are pinpointed. Data for children less than five was only available through 2015. Figure was constructed with data from the CDC ABCs bacterial surveillance program, 2016 reference 22.

Figure 2.

Trends in overall rate of IPD (invasive pneumonia disease), disease caused by PPSV23 included serotypes, and disease caused by PCV13 serotypes in different age groups between the years 1998–2016 in the United States. A) Children under 5, with only overall and PCV13 data available through 2015. B) Adults ages 19–64 C) Adults over 65. Figure was constructed with data from the CDC ABCs bacterial surveillance program, 2016 reference 22.