In a pre-print study published by the All India Institute of Medical Sciences, it was suggested that none of the vaccinated people died due to the COVID 19 infections during April-May 2021. This is the first study on breakthrough infections. 

The study investigations used genome sequencing, where most cases comprised B.1.617.2 and B.1.1.7 variants. The study clearly showed that viral load at the time of diagnosis was high in all the patients irrespective of vaccinations tatus or type of vaccine received. The initial course of disease with high-grade non-remitting fever lasted for about 5 to 7 days in the vaccinated group, similar to the clinical presentation in unvaccinated patients. 

It is important to mention here that none of the patients included in the study had any comorbidities that could make them susceptible to breakthrough infections. The report has said that “While antibody levels for a subset of patients were available, they became infected nevertheless and presented to the emergency just like other patients, putting in doubt the protection offered and/or clinical relevance of total immunoglobulin G as a surrogate of COVID-19 immunity.”