The second sero survey in Delhi, the results of which were released on Thursday, showed that 29.1% people have developed anti-bodies against Covid-19, Health Minister Satyendar Jain said. He said that the next exercise will begin from 1 September.
The first survey, conducted from 27 June-10 July by the Delhi government in association with the National Centre for Disease Control (NCDC), found that around 23% of people had been exposed to the coronavirus.
However, former AIIMS director Dr MC Misra told HuffPost India in an email interview that “herd immunity for Covid-19 illness is a far-fetched belief and a dangerous presumption”.
Delhi recorded 1,215 fresh coronavirus cases on Thursday, taking the tally to over 1.57 lakh, while the death toll from the disease has risen to 4,257, according to the health bulletin issued by the government.
The Kejriwal government has been praised for Delhi’s turnaround in containing the number of Covid cases (see here and here) after widespread panic gripped the city in May and June. From an average of over 3,000 daily cases for the week ending June 28, the number fell to 1,010 on August 2, according to a News18 analysis.
But concerns have been raised over Delhi relying more on antigen tests, which are considered less reliable, instead of RT-PCR tests. On Monday, 14,988 tests were conducted in Delhi and out of these, 10,882 were antigen tests.
Delhi Deputy Chief Minister Manish Sisodia said that Rapid Antigen Test has its own merits, one of which is giving immediate results that can help in early isolation of a patient to contain the spread of the virus, according to PTI.
Misra also concurred that antigen tests are quicker and less expensive. Delhi is conducting a high number of tests per million (72,378 according to Thursday’s bulletin) which could not have been achieved only by RT-PCR, he said.
Misra also said that testing can be ramped up by complementing RT-PCR tests with antigen tests, which is extremely helpful for initially screening the population in clusters.
1. After the results of the first sero survey showed 24% people had antibodies, Arvind Kejriwal said Delhi is moving towards herd immunity. How right or wrong is this assessment?
Let us understand what herd immunity is. Herd Immunity is termed when in a particular geographic region, majority of the population (60-70%) has had the infection (bacterial or viral, providing long-term immunity to these individuals and they are unlikely to contract infection again) and this will break the chain of transmission by not passing the disease to others. However, those who have not developed immunity and have compromised immunity (post-transplant, cancer chemotherapy, elderly with comorbidities) may still contract the disease as and when they get the inoculum of virus and/or are exposed to the virus in sufficient quantity.
Alternatively, herd immunity is achieved following mass vaccination (like Polio in 2011, smallpox in 1975) of the majority population of India and globally. To wait or hope that the majority population (60-70%) gets Covid infection to build immunity seems wishful thinking because people who have recovered from Covid are again contracting the illness. Therefore, Covid infection per se is unlikely to provide long lasting antibodies providing cell mediated immunity.
On the contrary, there are studies undertaken on a small number of recovered patients suggesting that the antibodies thus formed are fast disappearing. Therefore, herd immunity for Covid-19 illness is a far-fetched belief and dangerous presumption. It was one of the suggestions by the British Prime Minister back in March 2020, which was severely criticised.
2. Delhi on Monday conducted around 14,988 tests — 10,882 through rapid antigen and only 4,106 using RT-PCR. Is Delhi’s method of depending on more antigen tests leading to underestimation of cases? What are the problems associated with antigen tests?
Delhi has ramped up testing since mid-June by adding antigen tests. The result of an antigen test, when positive, is considered positive. It is quick and less expensive. Today, Delhi is doing the maximum number of tests per million (72,378 according to Thursday’s bulletin) which could not have been achieved only by RT-PCR.
If a person has symptoms then a negative antigen and/or RT-PCR test result does not mean much. The test has to be repeated. Even RT-PCR test has a 30% false negative rate. Negative rate is due to improper sample collection. Problem is not with antigen testing, but with the faulty method of sample collection for testing.
3. ICMR says if a person is symptomatic and the rapid antigen test results are negative, it should be followed by an RT-PCR test to confirm the diagnosis. Is this being followed in the capital?
Largely, it is being followed.
4. Is this a model followed by other states as well where more tests are conducted through the rapid antigen method?
Yes, testing can be ramped up by complementing with antigen testing, which is extremely helpful for initially screening the population in clusters where there is more infection in the community. By training those taking samples for antigen testing, its yield can be increased significantly.
5. There were several reports and accounts of shortage of hospital beds in Delhi in June. Are there adequate facilities available now?
The hospital beds situation has improved significantly because of the focus on home quarantine and follow-up. People are also agreeing to stay at home after realising that most Covid-nfected people have been recovering without consequences. Sisodia had painted an extremely grim picture of Delhi in June. He had said that by July-end, the number of cases in Delhi will grow to 550,000 and there will be a need of 80,000 hospital beds. Situation has remained quite under control, contrary to those projections. It has been possible by ramping up the testing, containment, home quarantine. Contact tracing has not been very successful, otherwise the situation could have been even better.
6. Is Delhi past its peak?
Average growth rate in Delhi has come below 1% (0.7%) during the 11- 18 August week. We will have to wait till August end to see if this trend is sustained. Then we can say that “Delhi is past its peak”.