The Delta variant of COVID-19 shows eightfold reduced sensitivity to the antibodies produced by coronavirus vaccine compared to the original Wuhan strain, according to a study from India with scientists from Cambridge Institute of Therapeutic Immunology & Infectious Disease.

"In an analysis of vaccine breakthrough in over 100 healthcare workers across three centres in India, the Delta variant not only dominates vaccine-breakthrough infections with higher respiratory viral loads compared to non-delta infections, but also generates greater transmission between HCW as compared to B.1.1.7 or B.1.617.1," the study found.

The study found that the Delta variant:

• Shows 8 fold reduction in sensitivity to antibodies

• Dominates breakthrough infections with higher viral loads

• Generates greater transmission between HCWs

The study further said that the mutant variant has enhanced spike proteins for attachment to the lung epithelial cells, which had provided it with a much higher capacity to infect many more people than the Wuhan strain.

These mutations are bound to happen if we lower our guard and allow ourselves to fall prey to this virus giving it an opportunity to multiply and achieve better fitness with our Covid inappropriate behavior," Dr Wattal, said.

“This is a straight eye opener to the fully-vaccinated people that you cannot lower guard in the name of vaccination. Virus is on prowl still looking of its prey," Dr Wattal added.

The study pointed that the dominance of the Delta variant has been due to combination of evasion of neutralising antibodies in those who were infected earlier and increased virus infectivity, resulting in the second wave.

According to the study, India's second wave was fuelled by:

• Evasion of neutralising antibodies in previously infected individuals

• Increased virus infectivity

While severe disease in fully vaccinated HCWs was rare, breakthrough transmission clusters in hospitals associated with the Delta variant are concerning and indicate that infection control measures need continue in the post-vaccination era, the study added.

The B.1.617.2 (Delta) variant was first identified in Maharashtra in late 2020 and has spread throughout the country, displacing the B.1.1.7 (Alpha) variant and other pre-existing lineages. It has also been found in at least 92 countries worldwide.