Hybrid immunity, which is developed as a result of vaccination and natural infection, may work well in providing protection against new variants of SARS-CoV-2, said experts.

Vaccination status

At present, more than 55 per cent of the adult population in India is fully vaccinated and over 87 per cent have received at least one dose of the Covid vaccine. It indicates that a large proportion of the population has developed hybrid immunity, according to Dr Vikas Bhatia, Director, AIIMS, Bibinagar.

“When a human body is exposed to a natural infection or is being inoculated, it generates an immune response that helps it fight infections in future. This helps protect the body against pathogens such as Covid, which may lead to severe disease or even death. Hybrid immunity is believed to provide greater protection against SARS-CoV2 variants,” Bhatia stated.

Delta wave

Meanwhile, according to Dr Padmanabha Shenoy, Consultant Rheumatologist and Medical Director, Center for Arthritis and Rheumatism Excellence (CARE), Kerala, close to 70 per cent of the population was affected by the Delta wave. According to him, hybrid immunity may prevent a huge Omicron wave.

“With more than 30 mutations in the spike protein, Omicron has the capability to evade the immune response generated by vaccines or previous infection alone. But hybrid immunity, created by a combination of these, may form a stronger wall against this formidable enemy,” he said.

“In India, we are following up with 1,500 patients with rheumatic diseases to know more about their immunity levels. When we analysed a subset of these patients, we found that a fully-vaccinated individual, on average, has anti spike antibody titres of 250; those who developed immunity after infection and vaccination have antibody titres exceeding 6,000,” he further added.

“This dramatic increase in the antibody titres provides robust protection against Covid infection. The research, which was recently published by Lancet journal, shows that those who have received a vaccine following infection were able to neutralise 87 per cent of the virus, compared to 56 per cent in the double-vaccinated group,” he added.

“We believe that hybrid immunity provides better protection than just a vaccination alone or just contracting the disease once. With Omicron, there are so many things we don’t know – how seriously it affects people, what are serious cases it leads to following the infection. It is a bit hard to say,” Dr Gautam Menon, professor of physics and biology at Ashoka University, told BusinessLine.

“However, we can guess about the protection by hybrid immunity on the basis of the cases that we have seen in South Africa, the UK and now in Norway. There is some hope and expectation that this is the case, but we do not know for sure,” Menon added.

Covid protocol

Though hybrid immunity will give protection, the experts cautioned against complacency when it comes to Covid-appropriate behaviour.

“It is important for us to follow personal protective measures such as wearing masks, maintaining a safe distance, avoiding gatherings, and sanitising hands regularly. Besides, those who have not taken their first or second dose of vaccine, should now take it on a priority basis,” said Dr Bhatia of AIIMS.

“There should not be any room for complacency. First, in India, about 25 per cent of people were not affected by the Delta variant, hence, they are susceptible to contracting the infection.

Second, about two crore people are immunecompromised and are at a high risk of developing severe disease even after vaccination. Besides, people with a compromised immune system, such as cancer patients, people with HIV and organ transplant, may harbour a virus variant for a long time, which may lead to the emergence of new mutants,” said Dr Shenoy of CARE.

Also, those who have had the infection post-vaccination, such as healthcare and frontline workers – who were first to receive the jab after the vaccination drive began in India in January – may not have the same degree of immunity as those who first had an infection and later took the vaccine.

Healthcare workers also have greater exposure to infection. Given India’s huge population, these factors make a large number of people vulnerable to catching the infection, according to Dr Shenoy.