New Delhi: At a time when incidents of breakthrough infections have raised a fear psychosis, a study conducted by the All India Institute of Medical Science (AIIMS) has revealed that no mortality takes place among people inoculated with two doses of Covid19 vaccines.
The study was conducted, during the April-May period, to find out the impact of breakthrough infections. It elaborated genomic analysis of isolates from breakthrough infections following vaccination with Covishield and Covaxin.
The study finds that variants of concern B.1.617.2 and B.1.1.7 responsible for cases surge in April-May 2021 in Delhi, were the predominant lineages among breakthrough infections.
“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,” the findings of the study said.
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The patients included health care workers (24 from AIIMS) and close analysis of the genomic sequences suggest that the samples clustered separately with origins closely clustering with lineages from different states, suggesting the disease transmission happened most likely from different and independent sources.
“Reinfections and vaccine breakthrough infections are rare occurrences and genomic sequencing of vaccine breakthrough infections can provide useful insights. In the present group of vaccine breakthrough infections investigated using genome sequencing, closely overlapping and mirroring the COVID-19 cases in the state of Delhi, the variants of concern B.1.617.2 and B.1.1.7 comprised the majority, but the proportions were not significantly different in comparison with the population prevalence of the variants during the period,” the study said.
It further said that while a number of vaccine breakthrough infections have been reported previously, it has been largely associated with non-severe symptoms. “During the subsequent course of illness, neither disease worsening (stable biomarkers) nor mortality was reported in the present group, confirming the previous observations. 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-19 immunity,” it said.
Study material and method: Samples were collected as part of routine testing for patients reporting to the Emergency Department at the All India Institute of Medical Sciences, with symptoms of high-grade fever, shortness of breath and headache. The samples were subjected to whole-genome sequencing.
All individuals who completed the schedule of vaccine and tested positive for SARS-CoV-2 on quantitative real-time polymerase chain reaction (qRT-PCR) test were included in the analysis. The cohort was subdivided into two groups depending on whether they received only one dose or both doses as per the vaccination schedule. Additional metadata including the dates of vaccination, type of vaccine received, dates of testing positive, clinical information including symptoms and history of forward transmission as well as occupation were elicited.
The study said that immunity acquired from natural COVID-19 infection or vaccines is not absolute and reinfections post-natural COVID-19 infections, as well as vaccine breakthrough infections, are not uncommon.
The recent evidence from the United States suggests vaccine breakthrough infections to be approximately 0.01 percent in fully vaccinated populations. One of the initial surveillance reports from a chronic care medical facility in India reported out of a total of 113 employees, 19 experienced vaccine breakthrough infections.
