Reinfections of COVID-19 with and Without Fourth Dose of Bivalent mRNA Vaccine in the Period from October 2022 to October 2023 in a General Medicine Office in Toledo (Spain)

Abstract

Background: Clinical-epidemiological differences between cases of covid-19 reinfections in people vaccinated with the 4th dose of bivalent mRNA versus cases of covid-19 reinfections in people not vaccinated with the 4th dose of bivalent mRNA are unknown. Objective: Compare the cases of covid-19 reinfections in people vaccinated with the 4th dose with bivalent mRNA vaccines versus cases of covid-19 reinfection in people not vaccinated with the 4th dose. Methodology: An observational, longitudinal and prospective case series study of adult patients with covid-19 reinfections in general medicine from October 1, 2022 to October 1, 2023. Results: 12 covid-19 reinfections were included in the period from October 2022 to October 2023. Of them, 5 were in people with fourth vaccine dose of bivalent mRNA and 7 in people without fourth vaccine dose of bivalent mRNA. There were no statistically significant differences by sex, age, psychosocial factors, severity of infection, symptoms, or in the comparison of chronic diseases by groups. A statistically significant difference was only found in the total presence of chronic diseases: 100% in covid-19 reinfections with fourth vaccine dose of bivalent mRNA versus 29% in covid-19 reinfections without fourth vaccine dose of bivalent mRNA. Conclusion: In the context of general medicine in Toledo (Spain), reinfections are rare, but the presence of chronic diseases represents a significant risk factor for covid-19 reinfections even if these people have fourth vaccine dose of bivalent mRNA. However, number of reinfections was possibly underestimated. The results should be taken with caution due to the small number of covid-19 cases included.