Study of Pneumococcal Infection May Point Way to Improved Prevention

A study of adults with invasive pneumococcal disease suggests that smokers and those who abuse alcohol should be targeted for pneumococcal vaccination.

Adult invasive pneumococcal disease (IPD) is a scourge for the elderly and patients with comorbidities. Improved understanding of IPD’s clinical characteristics, serotypes, and genotypes could help public health officials launch more effective prevention campaigns.

Toward that end, researchers from the University of Barcelona studied 745 culture-proven cases of IPD in adult patients aged 18 to 64 years from 1996 to 2010 and published their results online on August 13, 2012, in PLoS One. They stratified patients into 2 groups: adults with comorbidities and healthy adults with no prior or concurrent diagnosis of a chronic or immunosuppressive underlying disease. Patients with comorbidities accounted for 525 (70%) of cases. The remaining 220 (30%) occurred in healthy adults.

The “healthy adults” label was somewhat misleading, however, as many of the healthy adults who developed IPD were smokers (56%) or alcohol abusers (18%). They tended to be younger, were more likely to be female, and were less likely to die from IPD or complications compared with those with comorbidities. The most frequent IPD was pneumonia with empyema (pus in the pleural space), and the most common cause was infection with non-PCV7 serotypes, including serotypes 1, 7F, and 5. Empyema was most frequently caused by serotype 1.

The researchers found an emergence of virulent clonal-types Sweden1-ST306 and Netherlands7F-ST191. These clonal types tend to be more aggressive, more likely to cause pneumonia, and more resistant to antibiotics than other strains. The vaccine serotype coverage with the 13-valent pneumococcal conjugate vaccine (Prevnar, PCV13) was 82% in healthy adults, but only 56% in patients with comorbidities.

These findings provide more support for aggressive pneumococcal prevention campaigns, especially those that incorporate tobacco and alcohol abuse cessation programs and pneumococcal vaccination in active smokers and alcohol abusers.

A 2011 study conducted in Calgary, Canada also identified smoking as a risk factor for IPD. Additionally, they found illicit drug abusers, homeless people, and asthmatics at increased risk.

Ms. Wick is a visiting professor at the University of Connecticut School of Pharmacy and a freelance writer from Virginia.