The experts have been reiterating time and again that vaccine shots do not guarantee protection against the novel coronavirus infection but it certainly ensures that the infection does not become severe. As the Covid-19 cases are on a decline in the country and India reported less than 1 lakh cases for the third consecutive day today, a study conducted by the All India Institute of Medical Science (AIIMS) Delhi has highlighted the impact of the Delta Covid variant in India. The study has claimed that the Delta variant can not only infect people vaccinated with both Covishield and Covaxin vaccines but it is also a predominant mutant of the virus affecting the masses.
What does AIIMS study say
A small study was conducted on 63 people of which 35 patients received two doses, while 27 had received one dose of vaccine. Among the 63 participants, ten patients received Covishield while 53 had taken Covaxin shots, the AIIMS study said.
The patients included health care workers (24, 13 of which were from the same hospital) 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.
The study also made the comment on the prevalence of Delta variant in Delhi and said, “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 this period with high community transmission.”
The study has not been peer-reviewed yet.
What is the Delta variant of Covid-19?
There are multiple SARS-CoV-2 variants that are circulating across the globe. One of them is B.1.617.2, known as the Delta variant, which is more transmissible. Transmissibility appears greater than wild type (first wave) SARS-CoV-2 Delta continues to demonstrate a substantially increased growth rate compared to Alpha, across multiple analyses. Delta cases are rising whilst Alpha cases are declining. There is in vitro evidence suggestive of increased replication in biological systems that model human airway. It is highly likely that Delta is significantly more transmissible than Alpha.
Public Health England (PHE) says there are analyses from England and Scotland supporting a reduction in vaccine effectiveness for Delta compared to Alpha. This is more pronounced after one dose. “The iterated analysis continues to show that vaccine effectiveness against Delta is higher after 2 doses but that there is a reduction in effectiveness is seen for Delta as compared to Alpha. There is a high level of uncertainty around the magnitude of the change in vaccine effectiveness after 2 doses of Oxford-AstraZeneca vaccine,” it said.
“Delta is predominant and all analyses find that it has a very substantial growth advantage. The observed high growth rate is most likely to be due to a combination of place based context, transmissibility and immune escape. Both English and Scottish analyses continue to support the finding of reduced vaccine effectiveness which has increased to high confidence. New early data from England and Scotland suggest a possible increased risk of hospitalisation compared to Alpha. The priority investigations are vaccine effectiveness against hospitalisation and transmission, household secondary attack rate corrected for vaccination, characterisation of the generation time, viral load and period of infectivity, and epidemiological studies of reinfections,” it said.
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