Deadline for second sero survey extended till Aug 7
Around 15,000 blood samples – half of which will be from people between the ages of 18 and 49 -- will be collected from across Delhi between August 1 and 5.Updated: Aug 05, 2020 01:43 IST
The results of Delhi’s second serological survey for Covid-19 are likely to be announced by August 10, senior government officials said on Tuesday even as the deadline for the collection of samples was extended by two days till August 7.
Around 15,000 blood samples – half of which will be from people between the ages of 18 and 49 -- will be collected from across Delhi between August 1 and 5, according to guidelines released by the state government for the city’s second serological survey for Covid-19 will be carried out, setting a target that is slightly lower than the previous such study.
Delhi health minister Satyendar Jain on Tuesday said, “We will have to extend the serological survey in Delhi by two more days. Around 15,000 samples will be collected for the survey.”
The extension, the official said, is on account of two festival holidays -- Eid-ul Zuha on Saturday and Rakshabandhan on Monday -- that led to a reduction in the number of people who came to centres to get their blood drawn.
The findings of the study will help determine how much closer Delhi has gotten to the herd immunity threshold after the first serological survey in Delhi covering close to 21,800 people between June 27 and July 10, showed 22.86% of those tested had antibodies and we thus possibly immune to the Sars-Cov-2 virus that causes Covid-19.
The sample collection for the second round started on August 1 in four districts – North, Northwest, New Delhi and South. In all, 15,015 samples – from a cross-section of people selected to represent Delhi’s population demographic and – will be collected and tested for Sars-Cov-2 antibodies that will indicate a past infection.
“The repeated sero-surveillance will help us understand what proportion of people has been exposed since the last round and tell us whether the circulation is still on. It will also help us understand the proportion of cases that actually need medical attention—what it shows so far is that a majority of the cases are asymptomatic or mildly symptomatic. However, we still do not know whether the presence of the antibodies will protect against a second infection and whether enough number of people with such protection can create a barrier and protect others from the infection,” said Dr Lalit Kant, former head of epidemiology at ICMR.
“If we go by the experience of other coronaviruses, the antibodies offer protection for a few months to a couple of years. But we do not know whether Sars-CoV-2 behaves like other viruses,” he said.
The highest number of samples has to be collected are from the Northwest district (2,200), followed by West (2,145), and Central (1,548). The fewest will be from New Delhi district, where 885 have to be collected, according to the break-up given in the standard operating procedure (SOP) of the government, a copy of which is with HT.
Each team, which can collect 25 to 40 samples a day, will consist of ASHA (Accredited Social Health Activist) workers, an auxiliary nurse midwife (ANM), a phlebotomist or a lab technician, and a community volunteer.
Samples will be processed in 18 laboratories across the Capital, in Delhi government and central government hospitals, including the NCDC laboratory.
Unlike the first round of the surveillance, where all of the samples had been collected door-to-door, the government has also allowed collection at selected spots and health centre. All those included in the previous sero-surveillance done between June 27 and July 10 will be excluded from the second round of the survey.
A serological survey in Mumbai in July end -- conducted only in three wards as against all 11 districts in Delhi -- found that 57% of those living in slums and 16% of non-slum dwellers had antibodies against the infection.