Say having a younger, healthier population moving about for work will help build herd immunity in a densely populated country like ours; the numerous positive, asymptomatic cases are a hopeful sign, they say
Swab testing being conducted at Worli. Pic/Ashish Raje
Even as the world is frantically seeking a cure for or a vaccine to curtail the spread of COVID-19, senior health experts in India feel that in a thickly populated country like ours, needs an individualised approach. This means ending the lockdown so that herd immunity can be developed. This immunity is an indirect protection from infectious diseases, which has worked well during pandemics like measles, H1N1, etc, where some people were affected while others became immune to it. Sweden has successfully adopted this method for COVID.
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Dr Wiqar Shaikh, senior allergy and asthma specialist, said, "This will be the only solution to tackle COVID-19. Interestingly, even in India, many who have tested positive for the virus were asymptomatic, which might be an indication of herd immunity developing. However, we have to be wary of these asymptomatic carriers as they can spread the virus to others with co-morbidities who are at a much higher risk of developing symptoms."
"A stringent lockdown in the country will not allow herd immunity to develop in India, and the fear is being touted by other COVID-affected countries like China, Europe, USA and even WHO has warned about a second wave of COVID-19 outbreak soon. If herd immunity is not developed in India, the second wave will spell disaster," Dr Shaikh said.
In Sweden, till date, there have been more than 22,000 COVID-19 affected patients out of a 10 million population and more than 2,600 deaths. However, the country has no stringent lockdown and their COVID-19 graph is showing a downturn.
Experts say
Shaikh added, "This virus is here to stay and our only solution is to develop herd immunity. Moreover herd immunity is more likely to work in our country because 90 per cent of our population is under 60 and herd immunity works best in a younger population."
Dr Ketan Vagholkar, professor and head of the department Surgery, DY Patil Medical College, said, "Traditional herd immunity refers to the proportion of people with immunity in a given population. The term herd effect is reduction of infection in the unimmunised segment as a result of immunising a proportion of the population. In the context of COVID-19, we are expecting a herd effect. The only option now is to achieve herd effect, which has shown good results in the past."
He added, "There are three ways this can take be achieved: a) Allowing a large part of the population to get infected. However, this will lead to extremely high mortality. b) Vaccination, which is not available at present. c) Take advantage of the lockdown to prevent rapid community spread. However, a gradual easing of the lockdown for the young working population will increase the infectivity of the virus in this group thereby leading to protective immunity."
He said, "It is the young who are responsible for the spread and need to be protected by herd immunity. Only then can herd effect be achieved," he said.
Dr Vagholkar added, "Testing of the swabs is important to achieve herd immunity. Individuals who are positive but asymptomatic must be clustered together, and those with symptoms must report to a designated hospital immediately. This will reduce community spread as well as COVID mortality."
About the assessment of herd immunity, Dr Vaghalokar explained that one needs to evaluate antibodies. Unfortunately, in COVID patients there is no consistent level of antibodies that can confer protection against future re-infection. This makes the concept of herd immunity and herd effect a little complicated and risky. However, the time has come to weigh the importance of life v/s livelihood, and with no treatments available, the concept of herd immunity should be seriously taken up, especially during lockdown.
Dr Vagholkar said the priority in easing the lockdown should be guided by medical experts to prevent a COVID surge. The government has achieved excellent control over community spread and kept the situation under control. Therefore, the advantage gained should be utilised for effective control of the spread during the lifting of lockdown.
Dr Om Shrivastava, a senior infectious disease expert, said, "It is too early to say anything. We will need to test more people. For every 10 people we test, at least six should have antibodies of a certain level to confirm herd immunity. We may have to eventually opt for herd immunity as a recourse."
How herd immunity works
Dr Wiqar Shaikh said in the absence of a vaccine, there had been in the past certain percentages of the population, who were exposed to a given infection, which resulted in 'herd immunity' for the entire population. For instance such an exercise was adopted in the influenza outbreak in 1918. Researchers at the time found that if nearly 33-44per cent of the actual population was exposed to the influenza virus, the remaining 67 to 56 per cent developed 'herd immunity'. This means the influenza virus could affect only a certain percentage of the population and not everyone. Similar percentages were during the outbreak of measles in the US in 1930, where nearly 90 per cent of the population was affected. The entire population developed herd immunity after that, Dr Shaikh said.
What the government needs to do
Dr Wiqar Shaikh said that in order to achieve herd immunity the Centre and states should end the lockdown in a staggered manner immediately. The lockdown should be stringent only in containment zones like Dharavi, Govandi, Mankhurd, etc, as people here are carriers. The rest of the population should be allowed to continue with their daily routine. But, theatres, malls banquets halls, religious places, swimming pools, gyms, restaurants and bars should be shut, and elderly people and small children stopped from venturing out until we have solid signs of herd immunity developing. And, because Maharashtra and Mumbai conduct the highest number of tests in the country, and also have the highest number of COVID positive patients they will have the best chance of developing herd immunity.
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