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Delhi Sero-Survey

  • 22 Jul 2020
  • 4 min read

Why in News

Recently, the National Centre for Disease Control (NCDC) conducted a sero-surveillance study for Covid-19 in New Delhi.

  • NCDC is under administrative control of the Directorate General of Health Services in the Union Ministry of Health and Family Welfare.

Key Points

  • Sero-surveillance:
    • Detects Specific Antibodies: It seeks to assess the prevalence of disease in a population by detecting the presence of specific antibodies against the virus.
    • Immunity Check: It can also be conducted to check if a person has developed immunity to certain diseases.
    • Past Infections: It indicates past infections (and which triggered an immune response), and is not used to detect active infections.
    • Tested Immunoglobulin G Using ELISA: The Sera (a part of blood) of samples were tested for IgG antibodies and Covid-19 infection using Covid Kavach ELISA kits approved by the Indian Council of Medical Research (ICMR).
      • IgG (Immunoglobulin G) is a type of antibody which develops in most Covid-19 patients (infections) at around two weeks after infection and remains in the blood even after recovery.
      • ELISA (Enzyme-Linked Immunosorbent Assay) is a test that detects and measures antibodies in blood
  • Coverage of the Latest Study:
    • Coverage Period: It was conducted from 27th June - 10th July 2020. It was done when the city was reporting over 3,000 cases a day.
    • Coverage Groups: A total 21,387 samples were randomly collected across the 11 districts of the capital, which were then divided into two groups, of less than 18 years and older.
  • Result:
    • 23.48% of the people surveyed had developed IgG antibodies, indicating they had been exposed to the novel coronavirus (SARS-CoV-2) that causes Covid-19, with a large number showing no symptoms (asymptomatic).
  • Government's Response:
    • Impact of Proactive Efforts: Only 23.48% were found to be infected in a study carried out in a city with several pockets of dense population, shows that the proactive efforts by the government to prevent the spread of Covid-19, including prompt lockdown, effective containment and surveillance measures, contact tracing and tracking, as well as citizens’ compliance had yielded benefits.
    • Challenges: The remaining proportion of the population (about 77%) is still vulnerable to contracting the novel coronavirus infection.
      • Containment measures need to continue with the same rigour.
      • Non-pharmacological interventions such as physical distancing, use of face mask/cover, hand hygiene, cough etiquette and avoidance of crowded places etc. must be followed strictly.
  • Concerns:
    • The 23.48% rate of seropositivity cannot be extrapolated over Delhi’s entire population.
    • Further, currently there isn’t enough scientific data available about the level and duration of immunity that the body will develop after a person tests Covid-positive.
  • Sero-surveillance in the Past:
    • ICMR had conducted a pilot sero-survey in April 2020 across 83 districts in 21 states.
    • The initial results, which are being peer-reviewed, suggested that the percentage of the general population that could have been infected was 0.73, with urban areas showing a higher prevalence of about 1.09%.

Way Forward

  • The robust data collected through the study will help in the disease control programme.
  • Such scientific studies are extremely important and should be performed from time to time to understand the lessons from the past.

Source: PIB

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