Thailand’s Influenza burden before and during COVID-19 pandemic and factors associated with 30-day mortality among influenza patients between 2016 and 2020

Abstract

Various studies have reported that the COVID-19 pandemic affected influenza infection trends and severity. This study aimed to analyze influenza infection patterns, severity, and factors associated with 30-day mortality among influenza patients before (2016-2019) and during the COVID-19 pandemic (2020). Using National Health Security Office data, we included weekly influenza admissions. We estimated morbidity and mortality per 100,000 persons and performed descriptive study in sex, age, geographic, influenza vaccination, underlying diseases, length of stay, and adjusted related weight (adjusted RW). Multiple logistic regression was used in inferential study. Our analysis, based on 219,365 inpatients, revealed 2 peaks in influenza admissions during rainy and winter seasons. The highest morbidity rate was found in 2019 then suddenly decreased in February 2020. Most cases were found in young children (0-4 years) in the northern and northeastern regions. The mortality rate increased from 0.38 to 0.74 per 100,000 persons during the COVID-19 period. Factors significantly correlated with mortality were described as being aged 50 years and over at pre-COVID-19 period, being aged 65 years and over during COVID-19 period, adjusted related weight, and comorbidities. Moreover, vaccination was less associated with death during pre-COVID-19 period. We suggest targeted risk awareness campaigns by public health agencies, especially for vulnerable groups, to prevent influenza-related deaths, notably among the elderly and those with multiple comorbidities. Despite reduced influenza morbidity during the COVID-19 pandemic, the mortality rates surged. Further studies should explore the quality of care for influenza patients during COVID-19 period and evaluated non-pharmaceutical interventions in preventing COVID-19, which likely played a role in reducing influenza.