‘Continue with precautions to avoid next corona wave’
wave is always there. That is the reason we want early immunization with vaccination for all so that we cross the 70% threshold required for herd immunity to develop in the population.”
Dr Trupti Gilada, Infectious Disease Specialist, Masina Hospital, said that the SARS COV-2 virus has undergone over 4,000 mutations around the world, but most of these have made little difference to how the virus functions. “It is normal for viruses to undergo mutations as they replicate. A few recent strains have caused some concern though. The UK strain has mutations that make it more transmissible but with this variant, there is no evidence that it will evade the vaccination or human immune response. Also, there is no evidence that it makes people sicker or kills more people. The South African variant has been worrisome too because of its unusually large number of mutations that have changed the shape of the spike protein, which the virus uses to attach to and infect human cells. It is believed that the mutations in this strain make it harder for some antibodies (formed in response to either a Covid-19
infection or a vaccine) to get a good grip and neutralize the virus. This makes the virus much more infectious or transmissible. Over the last three months in India, we are all already witnessing increasing complacency in the behaviour of people, with inconsistent masking and small and large social gatherings without any distancing norm. These already existing variants definitely raise concerns about newer strains in the future that may be more transmissible and/ or more dangerous. In the background of our dropping our guard, if these variants also evade people’s immunity, either acquired naturally or through vaccination, we are definitely in for a second wave,” Dr Gilada said.
Maharashtra, which was the worst affected state in India, may witness stability and a steady fall in terms of the number of Covid cases. Meanwhile, several doctors maintain that the country has developed some percentage of herd immunity and this has led to a drop in Covid cases.
Dr Hemalata Arora, Senior Consultant, Infectious Diseases & Internal Medicine, Nanavati Super Specialty Hospital, said: “It seems that we have developed some amount of herd immunity. But it’s difficult to estimate the exact percentage as it varies with the location, based on multiple factors such as active and past patient count, people movement, access to timely healthcare, infection awareness, etc. Multiple surveys of the Indian Council of Medical Research (ICMR) have yielded similar results. Moreover, herd immunity is determined by studying the antibody count of a group of individuals and while at times the antibody test may not detect enough antibodies for a ‘positive’ result, the person may have sufficient antibodies to fight off the infection. Thus, the concept of herd immunity in Covid infection is not very clearly understood, but it’s likely to be the reason for the drop in new cases.”
“The percentage or levels of herd immunity is different in different parts of the country or even a state. As we speak, Telangana is witnessing a rise in positive cases. On the other hand, densely populated areas such as Mumbai, which reported a large number of cases in the early stages of the pandemic have a low fresh case count. Most crowded areas of Mumbai like Dharavi haven’t reported a fresh case for several days.
However, the levels of herd immunity may substantially rise as the Covid vaccination drive takes off. The vaccine will be effective against all the strains and help us gain the much-needed immunity to end this prolonged pandemic,” Dr Arora added. “India is moving towards herd immunity. The ratio of people who have tested positive versus the people who are asymptomatic carriers probably will be 1:80. That’s the projected ratio. I think a large number of people would have gained sub-clinical infection and immunity. Over a period of time, the virus load in the country is also decreasing. People need to understand vaccines are important. Serum Institute’s Oxford-astrazeneca Covid-19 vaccine is vector-based. It is announced to be safe with a good efficacy of around 70%. Bharat Biotech’s vaccine is also vectorbased, which is made from a rabies vector virus. The advantage is it doesn’t only target the S-protein, but it also targets the N part of the protein. So, it has better coverage as far as the mutants are concerned. The vaccine program should be widely accepted. Wide acceptance is very important,” Dr Bagai said.