The Delta variant of COVID-19 can possibly shatter the vaccine cover, as SARS CoV-2 the virus which causes the disease has the potential to acquire deadly mutations, health experts said on 7 July.

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As new variants are formed, it causes change to the spike protein and the structure undergoes a complete change- a reason why it can render the current vaccines, originally designed to target the protein, ineffective. Spike proteins, on the surface of SARS CoV-2, are what enable the virus to attach to and enter our cells, and all current vaccines are directed against them. Changes on the spike protein can determine how far and quickly the virus can spread. "There is an alteration in the structure of the virus proteins due to mutations, which can bypass the targets of some vaccines. This means there is a possibility that the virus may elude the vaccine coverage," Dr Praveen Gupta, Director Neurology, Fortis Memorial Research Institute, Gurugram said.

When mutation changes, it can possibly breach vaccine protection. "There's no doubt about it. We hope the vaccine will work. But with mutation, the virus changes its structure to become a new virus, while the vaccine remains the same. As bacteria develops resistance, so can the virus change mutation," emphasised Dr S.P. Byotra, Chairman of Department of Medicine, Sir Ganga Ram Hospital (SGRH), New Delhi. A recent study by the SGRH revealed that the Delta variant of the COVID-19 virus shows eight-fold approximately reduced sensitivity to vaccine-elicited antibodies compared to the Wuhan strain.

The study, available online as a non-peer-reviewed preprint version in Research Square, noted that the Delta variant (B16172), first identified from India, not only dominates vaccine-breakthrough infections with higher respiratory viral loads compared to non-Delta infections, but also generates greater transmission between fully vaccinated people as compared to the other variants -- Alpha (B117), or Kappa (B16171).

The findings can be explained by the fact that despite high vaccination rates, Israel -- 60.6 per cent have received the first dose of the vaccine, while 5.18 million have received the second dose -- is seeing an outbreak of COVID-19 due to the Delta variant. Similar is the case with the UK (48.7 per cent) and the US (47.1 per cent) and other countries with reasonably high inoculation rates.

A recent study by Israeli researchers has also shown that Pfizer vaccine efficacy against COVID-19 has dropped to 64 per cent. However, this does not mean that we should not be vaccinated. All the current vaccines have shown to be effective against severe outcomes from COVID. The experts stressed that vaccinations undeniably play a great role in curbing the spread of COVID-19. "Vaccines offer protection. It could be lowered against new variants like Delta plus but still will confer protection. We shouldn't create unnecessary panic but there should not be complacency either," Dr H.K. Mahajan, Anaesthesiologist, Indian Spinal Injuries Centre, Vasant Kunj, said.

Does this open the case for booster shots?
"Yes, booster shots will be helpful. If a person has taken two regular doses of Covishield or Covaxin, then a third dose of Sputnik V in the form of a booster will be good and helpful. It will prevent new variants or mutations. Therefore, it may be a matter of time when people will use a booster dose with a new medicine to enjoy long term protection against Delta and Delta plus," Mahajan said. However, experts also noted that it is important to evaluate the need for boosters with time.

"We need to first understand how the mutant virus interacts with the vaccine induced immunity then only we can decide whether a booster will be sufficient or a new vaccine is needed," Gupta added.