Influenza vaccination decreased risk of influenza hospitalization in patients with diabetes

On average during six influenza seasons, the protective effect of the vaccine in preventing influenza hospitalization was 46% for current-season vaccination and 44% for vaccination in prior seasons only, a Spanish study found.

Influenza vaccination may cut the risk of influenza hospitalizations by almost 50% in patients with diabetes, a study found.

Researchers estimated the average effect of influenza vaccination status in preventing laboratory-confirmed influenza hospitalization from the 2013-2014 to 2018-2019 seasons in hospitals and primary health care centers in Navarre, Spain. They used a test-negative case-control design in inpatients with diabetes to compare vaccination status during the six flu seasons between lab-confirmed influenza cases and negative controls. They also estimated the influenza vaccination effect in a cohort of nondiabetic patients. Children younger than age 9 years, health care workers, and nursing home residents were excluded. Results were published online on May 15 by Clinical Infectious Diseases.

Of 1,670 patients with diabetes who were hospitalized with influenza-like illness and were tested, 569 (34%) were confirmed to have influenza and the remainder were test-negative controls. About 62% of patients were ages 65 to 84 years. Renal disease was less frequent among influenza cases than in controls (22% vs. 30%; P=0.001), but no other significant differences were observed between groups. Among the case-patients, 71% had been vaccinated against influenza in any of the five prior seasons and 58% had received the current-season vaccine, compared with 82% and 68% of the control patients, respectively (P<0.001 for both). On average, the protective effect in preventing influenza hospitalization was 46% (95% CI, 28% to 59%) for current-season vaccination and 44% (95% CI, 20% to 61%) for vaccination in prior seasons only. Among patients with diabetes who had confirmed influenza, current-season vaccination reduced the probability of hospitalization (adjusted odds ratio, 0.35; 95% CI, 0.15 to 0.79). These effects were similar to those found in 3,501 nondiabetic patients, including in subgroups of those ages 60 years and older and those with chronic conditions.

Among other limitations, the study authors noted that they were unable to distinguish between type 1 and type 2 diabetes. They added that in the study location, vaccination was recommended in patients ages 60 years or older and in those with risk factors and that only inactivated trivalent vaccine was administered. Therefore, care must be taken when generalizing the results to other places with different indications for vaccination, different vaccination coverage, or other types of vaccines, the authors said.

The authors noted that influenza vaccination has a similar effect in patients with diabetes compared to patients with other chronic conditions, and vaccination received in recent seasons may retain some protective effect in patients who were not vaccinated in the current season, and that even if it fails to prevent influenza in diabetic patients, vaccination reduces the possibility of hospitalization.

“All these results support the benefit of influenza vaccination among patients with diabetes mellitus, which is of special interest since diabetes has been associated to an increased risk of influenza-related complications and deaths,” they concluded.