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Males more frequently infected with invasive pneumococcal diseases
A recent analysis of CDC surveillance data suggested that male invasive pneumococcal disease rates were significantly greater than those of females from 1998 to 2013.
This disparity was evident regardless of race, and even persisted after the introduction of Prevnar 7 (7-valent pneumococcal conjugate vaccine, Pfizer; PCV7) and Prevnar 13 (13-valent pneumococcal conjugate vaccine, Pfizer; PCV13), according to Annabelle de St. Maurice, MD, MPH, of the pediatric infectious disease division at Vanderbilt University, Infectious Disease News Editorial Board Member William Schaffner, MD, of Vanderbilt University’s health policy department, and colleagues.
William Schaffner
“Although commonly overlooked, gender has been reported as a factor influencing the susceptibility to certain infections, including malaria, HIV, parasitic diseases and influenza,” they wrote. “Age, race and presence of comorbidities are well-recognized risk factors for [invasive pneumococcal disease (IPD)]; with the very young and elderly, black individuals and those with comorbidities having higher IPD rates than individuals without these characteristics. A few early studies have suggested that rates of IPD may be higher among males than females, but this has not been fully characterized.”
The researchers collected and examined all IPD incidence data reported to the CDC’s Tennessee Active Bacterial Core surveillance (ABCs) site from 1998 through 2013. They defined positive cases as those with positive sterile site cultures of Streptococcus pneumoniae, and classified the cases by clinical syndrome and comorbidity. When analyzing the data, the researchers stratified IPD rates by age group, race and pneumococcal vaccine era (pre-PCV7, 1998-1999; early-PCV7, 2001-2004; late-PCV7, 2006-2009; and post-PCV13, 2011-2013).
Researchers identified 8,383 IPD cases from more than 2.5 million Tennessee residents under surveillance during the study period. Case patients were most frequently adults aged 40 to 64 years (39% of cases) or at least aged 75 years (17%), and two-thirds presented with bacteremic pneumonia. Nearly half of all cases had at least one comorbidity, with a history of smoking (20%) and chronic lung disease (19%) being the most common.
Fifty-three percent of all IPD cases were male, with men generally demonstrating a higher rate of IPD than women throughout the study period. The disparity was significant among children aged younger than 2 years and adults aged 40 to 64 years, among whom males demonstrated IPD rates as high as twofold that of females. The trend persisted among these age groups after stratification by race. Although IPD rates declined after introduction of the vaccines, males aged younger than 2 years, 40 to 64 years and older than 74 years still experienced greater IPD burden than females of the same age.
Because comorbidity burdens were similar between genders, more investigation is needed to understand the true cause of these disparities, the researchers wrote. Further, they said that additional analyses throughout other regions of the U.S. are required to determine whether these findings are specific only to Tennessee.
“IPD rates among very young and middle-aged males were higher than among females,” the researchers wrote. “These observations highlight the need for more epidemiological and basic science research further investigating behavioral and biological explanations for gender disparities in susceptibility to infectious diseases.” – by Dave Muoio
Disclosure: de St. Maurice reports funding from Pfizer, and Schaffner reports relationships with Genentech, GlaxoSmithKline, Merck, Noravax and Pfizer. Please see the full study for a list of all other authors’ relevant financial disclosures.