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Express News Service
NEW DELHI: Majority of the breakthrough infections following vaccination with Covishield and Covaxin were caused by SARS CoV2 lineage B.1.617.2, which is a variant of concern (VoC), according to study based on the genomic analysis of vaccine breakthrough infections in collaboration with clinicians at the AIIMS, New Delhi.

The analysis included 63 cases of vaccine breakthrough infections in Delhi, out of which 36 patients received two doses, while 27 had received one dose of vaccine. Ten patients received Covishield while 53 received Covaxin.

“B.1.617.2 was found to be the predominant lineage with 23 samples (63.9%) out of which 12 were in fully vaccinated and 11 in partially vaccinated groups. Four samples with 11.1% and 1 sample with 2.8% were assigned the lineages B.1.617.1 and B.1.1.7 respectively,” according to the study in preprints.

The patients had a mean age of 37 (21-92), in which 41 were males and 22 were females. None of the patients had any comorbidities which could act as a predisposing factor for breakthrough infections. AIIMS collaborated with the CSIR Institute of Genomics and Integrative Biology (CSIR-IGIB) for the study.

Variants of concern B.1.617.2, first detected in India, and B.1.1.7, detected in Maharashtra, were responsible for cases surge in April-May 2021 in Delhi, were the predominant lineages among breakthrough infections.

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Of the breakthrough infection cases analysed, 10 patients (8 with double doses of vaccine and 2 with single vaccine dose) additionally had total Immunoglobulin G (IgG) antibodies assessed by Chemiluminescent Immunoassay (Siemens), of which 6 patients had IgG antibodies a month before the infection, while 4 had antibodies after the disease episode.

“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 IgG as a surrogate of Covid immunity,” the study noted.

Of the 63 cases of vaccine breakthrough infections, including 36 who received full doses, there are no reports of mortality even though almost all cases presented with high-grade unremitting fever for 5-7 days.

“Viral load at the time of diagnosis was high in all the patients irrespective of vaccination status or type of vaccine received. The initial course of disease with high-grade non-remitting fever lasted for five to seven days in the vaccinated group, similar to the clinical presentation in unvaccinated patients,” it further said.

The authors said the present report is unique in many aspects as this is one of the first reports of symptomatic vaccine breakthrough infections, and breakthrough infections in a tertiary care setting apart from being the earliest reports of breakthrough infections with BBV152/Covaxin and B.1.617.2 variant of SARS-CoV-2.