Delta strain eight times less sensitive
SARS-CoV-2 B.1.617.2 Delta Variant Emergence and Vaccine Breakthrough: Collaborative Study, from India with scientists from Cambridge Institute of Therapeutic Immunology and Infectious Disease, conducted on over 100 healthcare workers (HCWs) at three centres in India, including Sir Ganga Ram Hospital (SGRH), found that the B.1.617.2 Delta variant not only dominated vaccine-breakthrough infections with higher respiratory viral loads but also generated greater transmission among the fully vaccinated HCWs. The study is yet to be peer-reviewed. 
“From this study, it indicates that we have miles to go before we sleep in case of a pandemic,” said Dr Chand Wattal, chairperson of the Institute of Clinical Microbiology and Immunology at SGRH. These alterations are almost certain to occur if we let our guard down and fall prey to this virus, allowing it to multiply.”
He went on to say that this is an eye-opener for the fully vaccinated people that you cannot lower your guard in the name of vaccination. This mutant has come back with enhanced spike proteins for attachment to the lung epithelial cells that have provided it with a much higher capacity to infect many more than the Wuhan strain.
The study further stated that the combined epidemiological and in vitro data indicate that the dominance of the Delta variant in India had been most likely driven by a combination of evasion of neutralising antibodies in previously infected individuals and increased virus infectivity resulting in the second wave.
It added that severe disease in fully vaccinated HCWs was rare. However, breakthrough transmission clusters in hospitals associated with the Delta variant are concerning, indicating that infection control measures need to continue in the post-vaccination era.
Finally, it said that progression to severe disease and death, however, was low in all studies. Therefore, at the population scale, extensive vaccination will protect against moderate to severe disease and reduce hospitalisation due to the Delta variant.
