A 23-valent vaccine showed only low to moderate effectiveness in protecting older adults from pneumococcal pneumonia, researchers in Japan reported.
Researchers recommended further investigation to improve the vaccine’s impact.
“Although there is good evidence that PPV23 reduces the risk of invasive pneumococcal disease in older people, its protective effect against pneumonia is controversial,” Motoi Suzuki, MD, of the department of clinical medicine at the Institute of Tropical Medicine, Nagasaki University, and colleagues wrote. “To our knowledge, no study has assessed the serotype-specific effect of PPV23 against pneumococcal pneumonia.”
The researchers performed a multicenter prospective study on patients with community-onset pneumonia who visited four hospitals in Japan between Sept. 28, 2011 and Aug. 23, 2014 (n = 2,036). All patients were aged 65 years or older. Suzuki and colleagues collected Streptococcus pneumoniae from sputum and blood samples, serotyping the samples using the capsular Quellung method. The researchers also tested sputum samples using PCR assays, and used a urinary antigen test on urine samples.
Four hundred-nineteen (21%) patients tested positive for pneumococcal infection, and 522 (26%) were determined to have been vaccinated. The PPV23 had a 27.4% effectiveness against all pneumococcal pneumonia, Suzuki and colleagues reported (95% CI, 3.2-45.6). Effectiveness against serotypes in PPV23 was 33.5% (95% CI, 5.6-53.1), and effectiveness against non-PPV23 serotypes was 2%. The researchers reported no significant differences across the study’s subgroups. However, Suzuki and colleagues wrote, the vaccine was more effective in women, people aged younger than 75 years and patients with either health-care associated or lobar pneumonia.
In an accompanying editorial, Mathias W. Pletz, MD, PhD, of the Center for Infectious Diseases and Infection Control at Jena University Hospital, Thomas Kamradt, MD, of the Institute of Immunology at Jena University Hospital, Jena Germany, and Tobias Welte, MD, of Hanover Medical School, Hanover, Germany, pointed out that the study had found the vaccine waned in efficacy over time.
“On the basis of these data, revaccination with PPV23 at least every 5 years for immunocompetent patients and every 3 years for immunosuppressed patients seems to be required,” Pletz, Kamradt and Welte wrote. “In our opinion, these data support the decision of several advisory committees to recommend sequential vaccination – ie, PCV13 followed by PPV23 – even if such an approach has not yet been investigated in an efficacy or effectiveness study.”