Abstract: Objective To investigate the association of 25-hydroxyvitamin D₃(25-OH-D₃) and viral infection with asthma predictive index(API) in infants with recurrent wheezing.Methods A total of 106 infants with recurrent wheezing who were admitted to Department of Pediatrics, Handan Central Hospital from April 2020 to April 2021 were selected.According to the presence of API at admission, they were divided into two groups: an API-positive group(n=65) and an API-negative group(n=41). Both groups were compared for general information, serum 25-OH-D₃ level, the viral infection rate before recurrent wheezing, the type of infected virus, peripheral blood eosinophil(B-Eos) count and serum total immunoglobulin E(IgE) level.The influencing factors of API positive in infants with recurrent wheezing were analyzed by Logistic multi-factor regression model.The correlation between serum 25-OH-D₃ level, the viral infection rate of recurrent wheezing and B-Eos count and total serum IgE was analyzed by Spearman correlation coefficient model.All children were given symptomatic treatment, and the prognosis was recorded after 12 weeks of treatment. Infants with different prognosis were compared for their 25-OH-D₃ level, the viral infection rate of recurrent wheezing, and API positive rateat admission. The efficiency of each indicator for predicting the prognosis of infants was analyzed.Results The API-positive group showed decreases in serum 25-OH-D₃ level, the viral infection rate before recurrent wheezing, B-Eos count, and total serum IgE level, compared with the API-negative group(P<0.05).Serum 25-OH-D₃ level, viral infection, B-Eos count, and total serum IgE level were significantly associated with API positive in infants with recurrent wheezing(P<0.05).For the API-positive group, serum 25-OH-D₃ level was negatively correlated with B-Eos count and total serum IgE level, while the viral infection rate before recurrent wheezing was positively correlated with B-Eos count and total serum IgE level(P<0.05).After 12 weeks of treatment, infants with persistent wheezing presented lower serum 25-OH-D₃ levels, but a higher viral infection rate before recurrent wheezing and a higher API-positive rate than those without wheezing(P<0.05). The area under the curve(AUC) of serum 25-OH-D₃ levels at admission, viral infection, and API positive to predict the prognosis of infants with persistent wheezing were all >0.7, where the AUC of combined indicators was 0.907, which was the largest.Conclusions 25-OH-D₃ and viral infection are significantly associated with API in infants with recurrent wheezing, with good reference significance in predicting the prognosis of children.