Updated: July 6, 2021 7:09:19 am
An analysis of vaccine breakthrough infections in more than 100 healthcare workers across three Delhi hospitals shows that the Delta variant of Covid is the most prevalent in such infections after receiving the vaccine.
Breakthrough infections refer to infections contracted after receiving at least one dose of a vaccine. “Mathematical modelling indicates that the growth advantage is most likely explained by a combination of increased transmissibility and immune evasion. Indeed in vitro, the Delta variant is less sensitive to neutralising antibodies in sera from recovered individuals, with higher replication efficiency as compared to the Alpha variant,” stated the collaborative study — not yet peer reviewed — from India with scientists from Cambridge Institute of Therapeutic Immunology & Infectious Disease.
The samples were taken from healthcare workers in Sir Ganga Ram Hospital, Indraprastha Apollo Hospital, and Northern Railway Central Hospital. “The reason that the Delta variant is dominant in breakthrough infections is that it has developed spiked proteins in such a manner that it links to cells in a more powerful way. We call that affinity… The spike protein has gotten split like a forked tongue which increases the affinity with which it clings… The positive part is that, with vaccines, even if you get the infection it is likely to be mild to moderate and you are unlikely to die,” said Dr. Chand Wattal, Chairperson Institute of Clinical Microbiology & Immunology at sir Ganga Ram.
The study states that not only does the Delta variant dominate the vaccine breakthrough infections among the samples, it also leads to higher viral loads and that there is evidence for larger transmission clusters for Delta versus non-Delta infections in these HCWs.
It states, “In vitro, the Delta variant shows 8 fold approximately reduced sensitivity to vaccine-elicited antibodies compared to wild type Wuhan-1 bearing D614G.”
“Vaccine breakthrough clusters amongst HCW is of concern given that hospitals frequently treat individuals who may have suboptimal immune responses to vaccination due to comorbidity. Such patients could be at risk for severe disease following infection from HCW or other staff within hospital environments. Therefore strategies to boost vaccine responses against variants are warranted in HCW and attention to infection control procedures should be continued even in the post-vaccine era,” the study states.
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