Nearly 20 years ago, the 13-valent pneumococcal conjugate vaccine (PCV13) was introduced into the infant vaccination schedule in the United States. However, a new study has found that despite the herd protection observed in U.S. adults, a persistent burden of PCV13-type community-acquired pneumonia remains in that population. Here is what researchers found out.
Nearly 80% of the infectious disease–related deaths in the U.S. are caused by pneumonia and other lower respiratory tract infections. Most at risk are adults aged 65 years and older who have substantial morbidity and mortality related to community-acquired pneumonia (CAP) and are hospitalized more frequently with the disease compared with younger populations, according to a recent report.
The article in Vaccine notes the paucity of research on the burden of adult pneumococcal disease after the introduction of PCV13 into the U.S. infant-vaccination schedule.
The study, led by industry and St. Louis University researchers, points out that most data regarding pneumococcal serotypes are derived from invasive pneumococcal disease, which represents only a small percentage of all adult pneumococcal diseases.
“Understanding which pneumococcal serotypes cause pneumonia in adults is critical for informing current immunization policy,” according to the authors, who state that their objective was to measure the proportion of radiographically confirmed (CXR+) CAP caused by PCV13 serotypes in hospitalized U.S. adults.
For the observational, prospective surveillance study, investigators recruited hospitalized adults from 21 acute-care hospitals across 10 geographically dispersed cities in the U.S. between October 2013 and September 2016.
Clinical and demographic data were collected during hospitalization, with vital status ascertained 30 days after enrollment. The study team used culture from the respiratory tract and normally sterile sites, including blood and pleural fluid, to detect pneumococcal serotypes. In addition, a novel, Luminex-based, serotype-specific urinary antigen detection assay was used to detect serotypes included in PCV13.
Included in the final-analysis population were 12,055 eligible patients with CXR+ CAP. Participants had mean age of 64.1 years, with 52.7% aged 65 years or older. Chronic obstructive pulmonary disease (43.0%) and diabetes mellitus (28.6%) were common morbidities.
Researchers detected PCV13 serotypes in 552 (4.6%) of all patients and 265 (4.2%) of those aged 65 years or older. Among patients aged 18 to 64 years, PCV13 serotypes were detected in 3.8% to 5.3% of patients, depending on their risk status.
“After implementation of a pneumococcal conjugate vaccination program in U.S. children, and despite the herd protection observed in U.S. adults, a persistent burden of PCV13-type CAP remains in this population,” the authors conclude.
A key issue, according to the study, is that comorbid conditions such as chronic respiratory disease, chronic heart disease, diabetes mellitus, and high alcohol intake place patients at increased risk for CAP, more severe illness, and worse outcomes than otherwise healthy individuals. Adults with immunocompromising conditions such as HIV infection, chronic renal failure, leukemia, and lymphoma are at even higher risk of developing CAP, according to the report.
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