Vaccination against influenza was associated with a significantly reduced risk for influenza pneumonia requiring hospitalization among both children and adults, according to the results of a study published in JAMA.
“The estimated vaccine effectiveness was 57%,” Carlos G. Grijalva, MD, MPH, of the Department of Health Policy at Vanderbilt University School of Medicine, told Medical Economics. “This means that about 57% of hospitalizations due to influenza-associated pneumonia could be prevented through vaccination.”
According to Grijalva, pneumonia is the most important infectious cause of hospitalizations in the United States, causing more than 200,000 hospitalizations.
“This disease is associated with substantial suffering and it is also an important risk factor for mortality,” Grijalva said. “In addition, the disease results in a very large economic burden for the healthcare system. This is why effective strategies to reduce the morbidity and mortality associated with pneumonia are of great public health interest.”
The most effective strategy to prevent influenza infections is vaccination, according to Grijalva. Several studies have shown that influenza vaccines can prevent fever and acute respiratory symptoms associated with influenza infections. However, whether influenza vaccines can prevent more serious complications of influenza such as pneumonia is unclear.
For this analysis, Girjalva and colleagues used data from the Etiology of Pneumonia in the Community (EPIC) study, a prospective observational study of hospitalizations related to community-acquired pneumonia. They pulled data for patients aged 6 months or older who had been hospitalized for laboratory-confirmed influenza infection with vaccination status available.
“To ensure a proper evaluation of the association between influenza pneumonia risk and prior influenza vaccination, the study was restricted to influenza seasons and to patients with similar propensity to require hospital care,” the researchers wrote in the study. “Furthermore, vaccination information was actively collected, and only patients with pneumonia and verified influenza vaccination history were included in the main analysis.”
They identified 2,767 patients hospitalized for pneumonia. Of these patients, 5.9% had laboratory-confirmed influenza. They also identified patients hospitalized for pneumonia that was not caused by influenza and used them as controls.
Seventeen percent of the patients with influenza-associated pneumonia had been vaccinated against influenza compared with 29% of the control patients with influenza-negative pneumonia. This equated to an adjusted odds ratio of 0.43 (95% CI, 0.28-0.68).
The researchers found that compared with unvaccinated patients, patients who obtained an influenza vaccination were more likely to be older and white. In addition, certain comorbidities such as diabetes, chronic pulmonary obstructive disease, cardiovascular disease, and other chronic conditions were more prevalent among vaccinated patients.
Looking specifically at adults, 22% of patients with influenza-pneumonia were vaccinated compared with 30% of control patients (adjusted OR=0.59, 95% CI, 0.34-1.02).
In their discussion of the results, the researchers noted that the study is limited by its inclusion of only four geographical areas, which may make it difficult to generalize the results to other areas of the country.
Source: Medical Economics
