Severity of COVID-19 infection in vaccinated and unvaccinated patients and their outcome - a local experience

Background: The COVID-19 pandemic continues to pose a significant global health threat. In late 2020 and early 2021, multiple vaccines were authorized for emergency use, enabling mass vaccination campaigns. This study aimed to evaluate factors influencing COVID-19 severity (mild, moderate, severe) and outcomes (death or discharge) in vaccinated individuals presenting to a tertiary care hospital. Material and Methods: An observational study was conducted at Dr. Ziauddin Hospital Clifton, Karachi, Pakistan, from June to September 2021. We included patients aged 16 and above with RT-PCR-confirmed COVID-19 infection, categorized by vaccination status (unvaccinated, partially or fully vaccinated). The study analyzed variables such as age, gender, vaccination status, vaccine type, disease severity, day of presentation, hospital stay, and breakthrough infection duration. Data were analyzed using chi-square tests. A total of 341 patients were enrolled, with 219 vaccinated (V1) and 73 unvaccinated (V2). Results: The median age was 65 years, with 61% males. Among the patients, 45% were fully vaccinated, 13.2% partially vaccinated, and 41% unvaccinated. Disease severity was mild in 17.9%, moderate in 50.1%, and severe in 32%. Disease severity was significantly associated with age (p=0.01), vaccination status (p=0.00), and vaccine type (p=0.00). Time since the last vaccination also influenced breakthrough infections (p=0.00). Of the patients, 76.5% survived and 23.5% died. Disease outcomes were associated with age (p=0.02), severity (p=0.00), hospital stay (p=0.01), and vaccine type (p=0.01). Conclusion: Age and vaccine-related factors significantly influence disease severity, while additional factors beyond vaccination may impact disease outcomes. Further research is needed to explore these variables. Keywords: Vaccination, COVID-19, Severity, Immunization, SARS-CoV-2