CLINICAL SYMPTOMS AND RESPIRATORY COMPLICATIONS AMONG CHILDREN WITH SEASONAL INFLUENZA AT NATIONAL CHILDREN’S HOSPITAL, VIETNAM, 2020-2021: SEASONAL INFLUENZA AT NATIONAL CHILDREN'S HOSPITAL, VIET NAM

Seasonal influenza is a public health problem among children. In this study we aimed to determine the clinical manifestations and complications among children in Vietnam with seasonal influenza in order to inform influenza complication prevention programs. Study subjects were children aged <16 years diagnosed with and hospitalized for influenza at the Center for Tropical Diseases, National Children’s Hospital, Vietnam, during June 2020-July 2021. The study was conducted retrospectively. In each subject, a nasopharyngeal or tracheal aspirate for real-time polymerase chain reaction test was performed to determine the presence, group and subtype of influenza. A total of 200 subjects were included in the study (187 influenza A, 13 influenza B), 55% male. The mean age of our study subjects was 27.1 months. About one quarter (26.5%) of subjects had received an influenza vaccine within the previous 12 months and 73.5% had either received an influenza vaccine greater than 12 months previously or had never received an influenza vaccine. Eighty-four percent of subjects had the H3N2 subtype of influenza and 9.5% had the H1N1 subtype of influenza. The most common symptoms among study subjects were: fever (100.0%), cough (85.5%), runny nose (62.5%) and sore throat (58.5%). The most common complications among study subjects were febrile convulsion (45%), bronchopneumonia (41%) and respiratory failure (25.5%). Risk factors significantly associated with bronchopneumonia were: preterm birth (crude odds ratio) cOR= 2.4, 95% confidence interval (CI): 0.9-6.7, p = 0.038), subject age <24 months (cOR=5.5, 95% CI: 2.8-11.2, p<0.00001), having an underlying comorbid condition (cOR=5.5, 95% CI:2.2-8.3, p = 0.00001) and having a co-infection (cOR=32.4, 95% CI: 9.5-172.9, p<0.00001). The most common co-infections among study subjects were: Streptococcus pneumoniae (6%) and Haemophilus influenzae (5%). Study subjects who received oseltamivir within 48 hours of symptom onset had resolution of fever (3.5 ±standard deviation (SD) 2.2 days) significantly (p<0.05) earlier than those who received oseltamivir after 48 hours of symptoms (5.1±3.1 days). No deaths occurred in the study among study subjects. In summary, the most common clinical symptoms among our study subjects were fever, cough, runny nose and sore throat. Complications were common and consisted of febrile convulsions, bronchopneumonia and respiratory failure and these were more common among younger subjects or subjects with an underlying condition or a secondary bacterial or viral infection. We conclude the complication rates in our study population were high and underline the importance of education about influenza vaccinations and good hygiene in this study population.