18 Crore Indians May Already Have COVID Immunity: Thyrocare Data
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A private lab has made public its data of the antibody tests it conducted over 20 days across the country. The results are striking. The data indicates near 18 crore people in the country already have antibodies against the novel coronavirus.
Thyrocare took its data from 60,000 antibody tests conducted across 600 pin codes over 20 odd days. Their estimate is that nearly 15 percent of the country may already have antibodies against the novel coronavirus, with a variation of plus minus 3 percent.
"Ours is the fastest, data driven prediction. Unfortunately it's not getting the attention it deserves," said Dr A Velumani, Chairperson, Thyrocare Technologies, in an interview with FIT.
While this is not a randomised study, nor an official survey, but data from this reflects what is apparently in the second seroprevalence study conducted by the Indian Council of Medical Research (ICMR), India's apex research body, conducted in the beginning of June. That data, according to various leaked reports, indicates that 15 to 20 percent of the country may already have antibodies to coronavirus. ICMR is yet to make that data public.
Positivity Highest in Worst Hit Pin Codes
According to the data, the pin code with highest positivity is Bhiwandi, in Thane, at 44% which is in line with the actual lab confirmed cases of COVID-19 from the district. This followed by Peenya Dasarahalli area in Bengaluru at 44%, a city seeing a rapid rise in cases, followed by Anand Vihar in New Delhi (37.7%), Hyderabad Jubilee area (37.3%), Dahisar, Thane (36.7%) and Ghatkopkar West, Mumbai (36.7%) again.
Most of these pin codes fall in containment zones/red zones within the state, with the top five impacted states already reflected here.
It seems to be the lowest in area pin codes that have seen lower number of actual reported RT PCR confirmed cases. These include pin codes in cities that are badly affected, but there are areas within that are reporting less number of cases.
Lower positive rate is reported from Alibag, Mumbai, (0.7%), Vidyanagar, Bellary(0.9%), Ambethan, Pune (1.5%), Baghthala, Rewari (1.9%) and Raja Annamalaipuram in Chennai (3.3%).
How Do I Read This Data? Is There an Inherent Bias?
A household in Noida decided to get all its 15 members to undergo antibody testing. 4 out of 15 tested positive, none of them had any known exposure to the virus.
According to the data released by Thyrocare, of the tests conducted in Gautam Budh Nagar (where Noida falls), 23.7 percent came back positive, consistent with the microcosm of this household.
While curiosity drove this family to get tests, is there an inherent bias in the data? Would those who have had symptoms in the past be more inclined to get tested? A seroprevalance study conducted in Santa Clara county in the US in April came in for criticism for introducing a selection bias in their survey - they chose Facebook as a means of recruitment, which critics said possibly pulled in more people who believed they had exposure to the study.
Now, Thyrocare's data is not a study. It's not printed anywhere other than Twitter. But Dr Velumani says the profile of those who wanted to get tested is very different.
"We have not chosen whom to test, we have only tested those who wanted it. 80% was the requirement of the corporates, 15 percent was the requirement of residential societies and 5% was the demand of individuals. We covered pin codes from Nariman Point to Jamshedpur, so big and small cities are all covered."Dr A Velumani, Chairman and Founder, Thyrocare Technologies
If this is indeed the case, it cuts down possibility of bias. But again, if large corporates and factories are housed in specific pin codes, as is the case, it would possibly impact the numbers.
How Reliable are Antibody Tests?
Then comes the question of the quality of tests itself. Should you trust them? We tried to answer some of your questions here. Thyrocare relied on ELISA and CILA tests approved by the ICMR. National Institute of Virology, that came up with the Elisa test for COVID-19 claims it has high sensitivity and specificity.
Dare We Say, 'Community Transmission?'
ICMR has steadfastly denied there is any community transmission in the country. They base this on the 1st seroprevalence survey they conducted across India in April which indicated that only 0.73 percent of the country was infected by coronavirus.
In a recent press conference, Rajesh Bhushan, OSD, Ministry of Health, said, “We shouldn’t forget that 49 districts alone account for 80 percent of the total COVID-19 cases in India.” A Lancet report says 627 of 640 districts in India have cases of coronavirus.
The more recent 2nd seroprevalence survey indicates, according to many reports, the average prevalence of the infection at 20 percent in the population, but again it's not published yet.
Dr Velumani says unlike ICMR, his data is more standardised and more recent.
"ICMR data is not pan-India, it is done by different agencies in early June. It's mid-July and I have done a crisp nationwide survey, using a single laboratory and a single system, so we can compare across the country. I am not saying mine better, it is different."
We reached out to virologist, Prof Shahid Jameel, CEO, Welcome Trust DBT India Alliance, on what this set of data, and ICMR's second survey indicates for India.
"If, as the reports go, prevalence of the virus in the population is indeed 20 percent on average according to ICMR, and our country's population is 1.40 billion, that translates to 28 crore people. If you take the first seroprevalence survey results as well, in end April we had 0.73% population exposed to COVID-19, that's 1 crore people, and the doubling time on an average was 20 days, then by mid-July we should have 16 crore people with COVID-19."
From all indications, if indeed 15-20% of the population has been exposed to COVID-19, and the mortality remain very low, and our hospitals are not too overwhelmed, perhaps it is good news? And India need not run away from the term community transmission.
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Topics: Coronavirus 2019
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