Explained | What is seroprevalance and what does it tell us?

Serology helps determine the size of the outbreak of a disease or the extent to which a certain population has been infected

The Indian Council of Medical Research (ICMR) has conducted four serosurveys in India so far, the latest of which was done between June 14 and July 6 and stated that two-thirds of Indians have developed antibodies against Covid-19, but 40 crore are still vulnerable.

It also stated 67.6 per cent of India's population aged above six years has developed antibodies for Covid-19.

Also Read — Majority in big states have Covid-19 antibodies: Survey

Here's a look at what seroprevalence and serosurveys mean.

What are serology and seroprevalence?

Serology is the study of antibodies in blood serum. Antibodies are part of the human body's immune response to an infection or virus, like SARS-CoV-2. Covid-19's antibodies are detectable usually within the first few weeks after infection.

The presence of antibodies in a person means they were infected with the virus, irrespective of whether they had severe, mild, or no symptoms.

Seroprevalence is determined by a study conducted to measure the extent of an infection, measured by level of antibodies, in a population. The percentage of individuals in a population who have antibodies to infection is called seroprevalence. With a new virus, including Covid-19, initial seroprevalence is assumed to be low as the virus has not circulated before.

A positive result from a serology test may mean that a person was previously infected with the virus.

Why is this study done?

This testing helps determine the size of the outbreak of a disease or the extent to which a certain population has been infected or exposed to an infection. It helps capture unrecognised cases not detected during routine surveillance.