Delhi Sero-Survey

• 22 Jul 2020

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 27^th June - 10^th 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