In the study, we attempted to record the breakthrough cases reported through passive and voluntary reporting at various healthcare facilities from different districts of Odisha, their clinical presentation, requirement of hospitalization post infection and antibody titer against spike antigen.
Nasopharyngeal swab and serum samples were collected from vaccinated individuals through passive and voluntary reporting to various healthcare facilities of Odisha state to detect the SARS-CoV-2 infection, quantitative antibody titers and was correlated with demographic and clinical presentation and requirement of hospitalization post infection.
Out of 361 samples referred to the laboratory for confirmation of breakthrough infection, 274 samples were found to be positive after 14 days of receiving complete doses of the vaccines. More than 83.2% of the individuals were found to be symptomatic with 9.9% of those required hospitalization. The seropositivity in individuals receiving Covishield (96.7%) was significantly higher than in Covaxin (77.1%). Hospitalised patients were having less median antibody titers than individual in home isolation. The median age for breakthrough infection among the referred cases was 47.0 years (IQR: 28.0) with a significantly older age group among Covishield recipients. The median spike RBD IgG titre values for Covaxin and Covishield recipients were 213.5 AU/ml (IQR: 537.5) and 647.5 AU/ml (IQR: 1645.1) respectively.
The results reported here highlight the need for systematic data capture for the breakthrough infections to monitor the emergence of any vaccine escape variants and to plan the next steps in the COVID-19 vaccine development by understanding the link between clinical protection and measured immunity against SARS-CoV-2 infection.