October 10, 2014
PHILADELPHIA — The 13-valent pneumococcal conjugate vaccine yielded an efficacy rate of nearly 50% in preventing a first episode of vaccine-type community-acquired pneumonia in a cohort of healthy older individuals, according to findings presented here.
Susanne M. Huijts, MD, of the Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, Netherlands, said conjugate vaccines have demonstrated efficacy against invasive pneumococcal disease and otitis media in children, but they have not undergone investigation in healthy elderly populations.
In the current randomized, double-blind trial, researchers investigated the efficacy of 13vPnC (Pfizer) in the prevention of a first episode of vaccine-type CAP in a cohort of 84,496 participants aged 65 years or older in the Netherlands.
A first episode of vaccine-type CAP served as the primary endpoint. A first episode of nonbacteremic/noninvasive vaccine-type pneumococcal CAP or a first episode of vaccine-type invasive pneumococcal disease served as the secondary outcome measures.
Immunocompetent patients with no history of pneumococcal vaccination were included.
Clinicians used sterile site and/or a serotype-specific urinary antigen detection assay to identify incidence of pneumonia.
“We have been hampered by a lack of acute diagnostic methods,” Huijts said. “The serotype-specific urinary antigen assay has been developed and evaluated in adults with CAP.”
Huijts said the assay has a sensitivity of 97% and a specificity of 100%.
Clinicians randomly assigned participants 13vPnC or placebo in a 1:1 ratio. The final analysis included 42,237 individuals in the study group and 42,255 in the placebo group. Baseline characteristics were similar between the two groups.
Results of the per-protocol analysis indicated a vaccine efficacy rate of 45.56% (P=.0006) for a first episode of vaccine-type CAP; 45.00% (P=.0067) for a first episode of non-bacteremic, noninvasive vaccine-type CAP; and 75.00% (P=.0005) for the first episode of vaccine-type invasive pneumococcal disease.
The primary endpoint was evaluated by two or more clinical findings, chest X-ray, proof by culture or urinary antigen detection assay, according to Huijts. The secondary endpoint was determined by the assay, as well, and the invasive pneumococcal disease endpoint was determined by sterile site.
“Forty-nine episodes of vaccine-type CAP occurred in the vaccine arm, compared with 90 episodes in the placebo arm,” Huijts said.
There were 33 episodes of nonbacteremic, noninvasive vaccine-type CAP in the study arm and 60 episodes in the placebo arm. Seven episodes of vaccine-type invasive pneumococcal disease occurred in the study group, compared with 28 events among those receiving placebo.
“All of those were in the per-protocol analysis.”
Huijts added that vaccine efficacy decreased somewhat in the intention-to-treat population, but all results were statistically significant.
“In a post hoc analysis, we found that efficacy of the vaccine persisted throughout the duration of the study,” Huijts said. “The effect was durable through 4 years.”
The researchers did not observe significant differences between the two groups with regard to serious adverse events. The mortality rate was 7.1% in both groups.
“No deaths were considered vaccine-related,” Huijts said. “The numbers were very low and comparable between the two treatment arms.”
Participants were enrolled at community-based sites and home visits, according to Huijts. Clinicians conducted surveillance for CAP and invasive pneumococcal disease at hospitals in the areas of enrollment. – by Rob Volansky
For more information:
Bonten M. Abstract 595. Presented at: IDWeek 2014. Oct. 8-12; Philadelphia.
Disclosure: Huijts reports no relevant financial disclosures. The study was sponsored by Pfizer.