Obesity increases the risk of hospitalization due to viral respiratory infections, including influenza virus and more recently SARS-CoV-19. As an independent risk factor, obesity impairs the immune response to viral infections and decreases the effectivity of immunizations. Using influenza virus infection (IVI) as a proxy, we aimed to determine the impact of rapid weight loss after bariatric surgery (BaS) on the risk of hospitalization due to viral respiratory infections.


National Inpatient Sample (NIS) data from 2010 to 2015 was examined. Patients were classified as treatment and control groups: treatment subjects were defined as patients with previous history of BaS, and control subjects as patients with BMI >= 35 Kg/m2, and without history of BaS. The outcome of the study was any hospitalization with IVI as a primary diagnosis. Univariate analysis and a multivariate regression model were performed to assess the differences between groups.


There were a total of 2,300,845 subjects, 2,004,804 controls and 296,041 treatments. Univariate analysis showed that the hospitalization rate in the treatment group was significantly lower compared to the control group (0.007% vs. 0.019%, p<0.0001), which was confirmed after adjusting for covariables (control vs. treatment: OR = 2.21, p=0.001).


Rapid weight loss after BaS may decrease the risk of hospitalization due to viral respiratory infections, but further prospective studies are needed to confirm these results. We believe this should be translated into the development of similar studies to determine the impact of BaS upon the incidence and severity of Coronavirus Disease 2019 (COVID-19).