Flu vaccine effectiveness low among immunocompromised patients
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Influenza vaccine effectiveness was significantly lower among immunocompromised adults compared with nonimmunocompromised adults during the severe 2017-2018 influenza season, according to a study.
“The number of immunocompromised individuals has increased in the last several years, due to higher life expectancy and higher numbers of patients undergoing solid organ and stem cell transplants, advanced cancer treatment, and new immunomodulating and immunosuppressive drugs to treat autoimmune and inflammatory conditions,” Fernanda P. Silveira, MD, MS, FIDSA, associate professor of medicine and director of clinical operations for transplant infectious diseases at the University of Pittsburgh Medical Center, told Healio.
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“These immunocompromised individuals face an increased risk of infections, including influenza, and are at higher risk of influenza-related complications, such as increased frequency of hospitalization, intensive care unit admission, and death,” Silveira said.
According to Silveira, yearly influenza vaccination is recommended for immunocompromised patients, but there are few data regarding to what extent influenza vaccination protects them.
In their study, Silveira and colleagues analyzed data from 10 hospitals to understand influenza vaccine effectiveness among hospitalized immunocompromised adults. They included parients aged 18 years or older who were hospitalized with acute respiratory illness (ARI). Vaccine effectiveness (VE) was evaluated with a test-negative case-control design using multivariable logistic regression, with PCR-confirmed influenza as the outcome and vaccination status as the exposure, according to the study.
Among 3,524 adults hospitalized with ARI, 1,210 (34.3%) had an immunocompromising condition, Silveira and colleagues reported. These adults were more likely to be vaccinated than non immunocompromised individuals (69.5% vs. 65.2%), and less likely to have influenza (22% vs. 27.8%). According to the study, the overall VE against influenza hospitalization, including immunocompetent adults, was 33% (95% CI, 21%-44%), whereas VE among immunocompromised vs. nonimmunocompromised adults was lower at 5% (–29% to 31%) vs. 41% (27% to 52%) (P < .05 for interaction term).
Silveira said other studies have shown that patients with certain immunocompromising conditions such as organ transplant recipients and cancer patients have reduced humoral immune responses to influenza vaccination compared with healthy individuals.
“We don't know if different vaccine types improve VE, such as the use of high-dose or adjuvanted influenza vaccine,” she said. “We did not have enough power in our study to analyze different vaccine types or different causes of immunocompromise.”
According to Silveira, it is important to continue to study VE in the immunocompromised population, including studying if different vaccine formulations are associated with improved VE, but also to improve the vaccination rates of close contacts of immunocompromised patients, to create a circle of protection. For now, she said vaccine recommendations for immunocompromised patients are no different from the general public, “except for the use of live-attenuated influenza vaccine, which is contraindicated in immunocompromised individuals.”
“Until we know whether enhanced vaccines such as the high-dose and adjuvanted vaccines improve flu VE in the immunocompromised, decreasing the burden of influenza in immunocompromised individuals may be more dependent on improving vaccination rates of close contacts,” Silveira said. “Given these results, it is important to remember antiviral treatments for immunocompromised persons who contract influenza.”
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