ABSTRACT
Background Dengue which is endemic in India and has been occurring for decades apparently witnessed a rise in disease burden in 2021 in specific regions of the nation. We aim to explore less studied risk factors of Dengue occurrence and severity in the post-COVID-19 and post-COVID-19 vaccination era. Methods This was an exploratory analysis involving participants from two prior observational studies conducted during the period of Feb 2021-April 2022 in a tertiary hospital in North India. Healthcare workers constituted the majority of study participants. Individuals were stratified into five groups based on COVID-19 infection and timing of vaccination: CovidNoVaccine (CNV), VaccineNoCOVID (VNC), CovidAfterVaccine (CAV), VaccineAfterCOVID (VAC) and NoVaccineNoCovid (NVNC) groups. The occurrence of lab-confirmed Dengue and severe forms of Dengue were the main outcomes of interest. We tried to predict determinants of Dengue occurrence and severity with a particular focus on COVID-19 history and vaccination status. Results A total of 1520 vaccinated individuals and 181 unvaccinated individuals were included. Of these 1701 participants, symptomatic Dengue occurred in 133 (7.8%) and was of 'severe' category in 42 (31.6%). Individuals with a history of COVID-19 in 2020 had 2 times higher odds of developing symptomatic Dengue. The VAC group had 3.6, 2- and 1.9 times higher odds of developing Dengue than the NVNC, VNC, and CAV groups. The severity of dengue was not affected by COVID-19 or COVID-19 vaccination. Conclusions COVID-19 may enhance the risk of developing symptomatic dengue. Future research dealing with long COVID should explore the propensity of COVID-19 victims towards symptomatic forms of other viral illnesses. Individuals receiving the COVID-19 vaccine after recovering from COVID-19 particularly seem to be at greater risk of symptomatic dengue and need long-term watchfulness. Possible mechanisms, such as antibody-mediated enhancement or T-cell dysfunction, should be investigated in COVID-19-recovered and vaccinated individuals. Further large-scale, multicentric, robust studies with a better enrolment of unvaccinated people will help understand the interplay of factors involved in COVID-19 and Dengue.