SERO SURVEY

Subject : Science & tech

Context : Sero surveys to detect antibodies against COVID underestimate building of herd immunity.

Concept :

What was the serological survey about?

• The serological survey was meant to detect whether the person being tested had developed antibodies against the coronavirus.
• Since it is not possible to test everyone, detecting antibodies in random sets of people is an indirect way of estimating the extent of disease spread in a community.
• The antibodies are proteins produced by the immune system to fight external organisms like viruses that try to enter the body.
• These are produced only after the infection has happened, and are specific to the attacking virus or bacterium.
• The presence of antibodies, therefore, is an indication that an infection by that particular virus or bacterium has already occurred.
• Subsequent attempts to infect the body can be thwarted by these antibodies.

What about Vaccines then?

• Vaccines work in a similar manner – wherein they inject harmless doses of a virus or a bacterium inside the human body to trigger the production of antibodies by the immune system.
• These antibodies can then fight off an actual attack by those viruses or bacteria.

Do antibodies ensure Immunity?

• The mere presence of antibodies does not mean that the person is protected against the disease.
• What is also important is the amount of antibodies present, and whether it also includes what are known as “neutralising antibodies” which actually fight the disease.

What is Herd Immunity?

• Herd immunity is a stage of an epidemic in which some members of a population group remain protected from infection because a majority of those around them have already developed immunity, either through vaccination or because they have been infected earlier.
• Once a certain proportion of population gets infected, and thus builds immunity against the disease, the epidemic begins to slow down and eventually stop.
• No one clearly knows what percentage of the population needs to be infected before herd immunity kicks in. It is different for different diseases, and different population groups.