Disclosures: Kimball reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
January 23, 2021
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Older, immunosuppressed patients at higher risk for flu vaccine failure, complications

Disclosures: Kimball reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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A study found that older and immunosuppressed patients are at an increased risk for influenza vaccine failure and influenza complications, researchers reported.

“Much research has been done to look at different patient groups and their risks for vaccine failure,” Joanna Kimball, MD, assistant professor of internal medicine at the University of Kansas Medical Center, told Healio. “We wanted to review patients hospitalized with an acute influenza illness and evaluate for specific risk factors among patients vaccinated against influenza compared to those unvaccinated. By determining these risk factors, we hoped to better identify at-risk patient groups that could guide future influenza vaccine research and strategies.”

flu shot
Older and immunocompromised patients are at an increased risk for influenza vaccine failure and for influenza complications.
Credit: Adobe Stock

Kimball and colleagues evaluated patients admitted for an acute respiratory illness during the 2015-2019 influenza seasons to compare vaccinated, influenza-negative patients with vaccinated, influenza-positive patients.

According to the study, 1,236 patients vaccinated for influenza were enrolled in the study, of which 235 (19%) tested positive for influenza. The researchers found that demographics, vaccines and comorbidities were similar between the groups, except for morbid obesity, which occurred in 13% of participants in the influenza-negative group vs. 8% in the influenza-positive group (P = .04); and immunosuppression, which was present in 63% of participants in the influenza-positive vs. 54% in the influenza-negative group (P = .01).

A logistic regression analysis demonstrated that older patients (OR = 1.47; 95% CI, 1.03-2.1) and immunosuppressed patients (OR = 1.56; 95% CI, 1.15-2.12) were at increased risk for influenza despite immunization, the researchers reported. Additionally, when evaluated by influenza subtype, immunosuppression was found to increase the risk for influenza A (H3N2) (OR = 1.86; 95% CI, 1.25-2.75).

“What is most concerning about our findings is that the patients we found to be most at risk for influenza vaccine failure are also those considered to be at highest risk for influenza complications,” Kimball said. “We must find ways to protect these patients against influenza, whether with more effective vaccines, of which research is still underway, or with new vaccination strategies, such as encouraging vaccination of high-risk patients' close contacts.”