Did COVID-19 or COVID-19 vaccines influence the patterns of Dengue in 2021: An exploratory analysis of two observational studies from North India (preprint)

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.

The Pathogenetic Dilemma of Post-COVID-19 Mucormycosis in India (preprint)

There has been a surge of mucormycosis cases in India in the wake of the second wave of COVID-19 with more than 14000 cases reported. Mucormycosis in patients of COVID-19 in India is at variance to other countries where Aspergillus, Pneumocystis, and Candida have been reported to be the major secondary fungal pathogens. We discuss the probable causes of the mucormycosis epidemic in India. Whereas dysglycaemia and inappropriate steroid use have been widely suggested as tentative reasons, we explore other biological, iatrogenic, and environmental factors. The likelihood of a two-hit pathogenesis remains strong. We propose that COVID-19 itself provides the predisposition to invasive mucormycosis (first hit), through upregulation of GRP78 and downregulation of spleen tyrosine kinase involved in anti-fungal defense, as also through inhibition of CD8+ T-cell mediated immunity. The other iatrogenic and environmental factors may provide the second hit which may have resulted in the surge.

Of Cross-Immunity, Herd Immunity and Country-Specific Plans: Experiences from COVID-19 in India (preprint)

India has witnessed a high number of COVID-19 cases, but mortality has been quite low, and most cases have been asymptomatic or mild. In early April, we had hypothesized a low COVID-19 mortality in India, based on the concept of cross-immunity. The presence of cross-immunity is presumed to lead to a milder course of disease and allow the time necessary for the development of adaptive immunity by the body to eliminate the virus. Evidence supporting our hypothesis has started showing up. Multiple studies have shown the generation of different T cell subsets and B cells responding to epitopes of viral proteins, especially of the spike protein, as a part of adaptive immunity against SARS-CoV-2. Cross-reactive T-cells have been demonstrated in patients who have been previously exposed to endemic coronaviruses. The interplay of cross-immunity and herd immunity is apparent in the COVID-19 scenario in India by the presence of a large number of asymptomatic or mild cases, a low infection-fatality ratio and a generally flat curve of percentage positivity of cases with respect to total testing, both in periods of strict lock-down and step-wise unlocking. It seems that cross-immunity resulted in faster generation of herd immunity. Although the initial restrictive measures such as lockdown prevented the rapid spread of the outbreak, further extension of such measures and overly expensive ones such as enhanced testing in India will result in a huge burden on the health economics as well as the society. Hence, we propose a restructuring of the health services and approach to COVID-19. The restructured health services should move away from indiscriminate testing, isolation and quarantine, and instead, the emphasis should be on improving facilities for testing and management of only critical COVID cases and the replacement of complete lockdowns by the selective isolation and quarantine of the susceptible persons such as the aged and those with co-morbidities. In the process of describing India-specific plans, we emphasize why the development of country-specific plans for tackling epidemics is important, instead of adopting a “one policy fits all” approach.