Sero-surveillance: Why the delay

Sero-surveillance has been depended upon to identify trends of a certain disease, the burden of infection, predict potential outbreaks, new or emerging pathogens and in a way, help contribute to the rooting out of rampant infection.


We are indeed glad that the state health authorities have now decided to conduct sero-surveillance in the state in view of the rising number of Covid 19 positive cases. We have all along been advocating this measure so as to determine the character of the spread of Covid 19 in the state as against other states and other countries. The number of Covid 19 positive cases has exceeded 20,000 now, but the daily surge has come down from 200/300 to an average of 150 cases in the last few days while the recovery rate has increased. Yet, we cannot be complacent now as winter has already begun. While a vaccine or a definite treatment plan is not available to us, experts believe that the only way to prevent further spikes in infections or find out the actual data about exposure levels is to test the presence of antibodies in people.

Sero-surveillance is a globally used and trusted standard which measures the levels of antibodies against a certain infection and decodes the percentage of the population which has been previously exposed to the virus. In Delhi, the third round of sero-surveillance began from Oct. 15. A total of 15,164 samples will be taken. The national capital recorded 22 Covid-19 fatalities, as the toll mounted to 5,946 while 3,428 fresh cases took the tally to over 3.24 lakh. The tool is also used as a measure for officials to check on mass inoculation and see the level of immunity people have. Even before COVID-19, it was used as an extensive tool to see how far an infection has breached in a community. National sero-surveillance programs are well established in many countries worldwide.

Sero-surveys, conducted over time could also inform officials about statistical data regarding any disease. For example, with an infection as scary and rapidly spreading as COVID-19, a sero-survey could provide information about what percentage of the population in a given city or district may have acquired some sort of immunity to the virus. It could also give them inputs about what further measures to take, where the disease more concentrated is or the age groups which might be more at risk. Hence, sero-surveys done over a period of time, or conducted every month, just like what has been detailed, can be one of the ways to measure the spread of the disease or map consequent spikes of the infection.

Sero-surveys derive results from the presence of antibodies, proteins meant to fight off infections which are part of the body’s immunology make-up. For a sero-survey, sample blood tests are done and if the antibody levels in the blood are detected, it can mean that a person has considerable immunity against the said infection. Sero-surveys done routinely could also show how long do antibodies last in the body and provide immunity against the disease, which is a pressing concern.

Another benefit of sero-surveillance is to observe if a vaccine can actually provide immunity. Given that we have a vaccine ready for the masses by the end of 2020 or early 2021 (which may or may not be possible), a sero-survey could show if the COVID-19 vaccine being deployed to the masses is actually working. Sero surveys could also identify any infection cases (asymptomatic, mild ones, or ones which may have gone away on its own) which may have been missed.

Apart from this, sero-surveillance has also been depended upon to identify trends of a certain disease, the burden of infection, predict potential outbreaks, new or emerging pathogens and in a way, help contribute to the rooting out of rampant infection. In the past, sero-surveillance has been used to map the spread of diseases and infections like Hepatitis B, hepatitis C, diphtheria, tetanus, polio and mumps.
 

-Editorial
First Published:Nov. 12, 2020, 2:32 a.m.

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