Patterns and predictors of COVID-19 occurrence and severity in vaccinated priority groups
Authors: Kaur Upinder , Bala Sapna , Ojha Bisweswar , Pathak Bhairav Kumar , Joshi Aditi , Yadav Ashish Kumar , Singh Anup , Kansal Sangeeta , Chakrabarti Sankha Shubhra 
Published: December 2021

Background: Varying protection rates have been observed with approved COVID-19 vaccines post-approval, in various real-world studies. However, little data exists on the clinical presentation and risk factors of occurrence and severity of COVID-19 in vaccinated individuals. The aim of the present study is to describe the patterns of presentation of COVID-19 in vaccinated individuals, and to determine the predictors of occurrence of COVID-19 and the predictors of severity in the vaccinated.Methods: The study is a part of a prospective observational study ongoing since February 2021 in a tertiary teaching and research hospital of northern India. Individuals recruited in this study belong to a high-risk group comprising health care workers and elderly. COVISHIELD, based on ChAdOx1 nCoV-19 platform was the vaccine received by the participants based on policy on allocation.Primary outcomes of the study are the short term and long-term adverse events following immunization (AEFI) with COVID-19 vaccines. Secondary outcomes include the rates of occurrence of COVID-19 and severity of COVID-19. Data on these have been already reported. The clinical presentation, typical and atypical manifestations, time to symptomatic recovery and patterns of post-COVID-19 complaints were analysed in the current study. Logistic regression analysis was performed to predict the risk factors of occurrence of COVID-19 in the vaccinated and the determinants of severe forms of the disease in this group.Findings: 1500 individuals completed at least two month follow up. Of these, 418 developed laboratory confirmed or suspected COVID-19. Fever was the commonest symptom (72%), followed by features of rhinitis (41%) and cough (34%). Nearly 12% individuals had only one symptom or none. Cardiovascular involvement was seen in more than 2% of affected. Time to symptomatic recovery varied from 1-75 days and 11% had post COVID-19 complaints at two month follow up, most common being generalized weakness. Results of regression analysis showed 1.6 times higher odds of contracting the disease in females and young individuals < 40 years of age (P<0.001). Overweight individuals and those receiving only one dose were at 1.4 times and 3 times higher odds of contracting COVID-19 compared to those with normal body mass index and those who were fully vaccinated. Individuals receiving two doses at a gap of < 30 days were at 7 times higher odds of disease acquisition compared to those receiving the second dose at an extended gap of > 60 days (P=0.01).With respect to severity, males and those receiving only one dose each had 3 times higher odds of suffering from moderate to severe COVID-19 compared to females and fully vaccinated. Persons with pre-existing lung disease, such as asthma had 6 times higher odds of suffering from moderate to severe COVID-19 (P=0.024). No association with the occurrence or severity of disease was observed with any other co-morbidity or the use of renin-angiotensin-aldosterone system (RAAS) blockers.Interpretation: Sex wise differences exist with respect to occurrence and severity of COVID-19. Two doses of vaccine, compared to one dose provide considerable protection against occurrence as well as severity. Full vaccination with extended dosing interval should be the optimal strategy and should be carried out when the community burden of cases is negligible. Future studies are needed to explore the sex wise differences in the propensity and severity of COVID-19. Further, the risk association of asthma phenotypes with COVID-19 needs to be investigated.Funding: The study received no funding support