4th nationwide sero- survey: 3k samples sent for test from Bihar

Around 3,000 blood samples were collected and sent for test during Indian Council of Medical Research (ICMR)’s fourth nationwide serological survey in 70 districts, including six of Bihar

Around 3,000 blood samples were collected and sent for test during Indian Council of Medical Research (ICMR)’s fourth nationwide serological survey in 70 districts, including six of Bihar.

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The survey, conducted in the state between June 20 and 25, will ascertain prevalence, called seroprevalence or seropositivity, of antibodies against SARS-CoV-2 virus that causes Covid-19, from a past infection in a given population.

A seropositivity of over 70%-80% will help develop herd immunity, said scientists, as the government stepped up its vaccination drive beginning July 1.

“The results are expected in August. We have sent the samples for analysis to National Institute of Epidemiology, Chennai, to test them for presence of antibodies that determine a past infection due to the virus in an individual,” said Dr Krishna Pandey, director of ICMR’s Rajendra Memorial Research Institute of Medical Sciences (RMRIMS), Patna.

This is the first time that children of six years and above have been included in the survey, along with adults, given the presumption of a third wave of the pandemic affecting children, Dr Pandey said.

The first two surveys conducted in May and August last year were restricted to adults, while the third survey in December included persons aged 10 years and above, he said.

For the recent, as many as 500 samples were taken from each of the six districts--Arwal, Buxar, Begusarai, Muzaffarpur, Purnia and Muzaffarpur. Of these, 400 samples in each district were of the general populace and 100 of health care workers.

The selected district was divided into 10 clusters, each accounting for 40 samples from the general population. Four samples from every cluster were of children between six and nine years of age; 12 of children between 10 and 17 years, and remaining 24 of adults, said Dr (Major) Madhukar, nodal officer of Bihar for serological survey and Scientist B of RMRIMS.

This meant that of the 400-target group from the general populace in each district, 40 were children between six and nine years, 120 between 10 and 17 years, and remaining 240 adults, he added.

The samples and villages in districts were selected randomly. The last three serological surveys were also undertaken in the same six districts and clusters, but the recent survey has been undertaken in adjoining villages to those selected previously, said Dr Madhukar.

PAST SERO SURVEYS IN BIHAR

Muzaffarpur reported 0% seroprevalence during the first survey in May last year. Buxar reported 1.25%,, followed by 1% each in Arwal and Madhubani, Purnia 0.75% and Begusarai 0.25%.

Arwal reported the highest seroprevalence of 26.20% during the third survey in December. Buxar was next with 26.07%, followed by Madhubani 24.5%, Muzaffarpur 21.70%, Purnia 21.01% and Begusarai 15.01%.

“The cumulative seropositivity was 0.7% during the first survey undertaken between May 17 and 20 last year. This meant that only 17 out of 2,400 people surveyed developed antibodies (immunity) against SARS-CoV-2,” said Dr Madhukar.

The seropositivity rate in Bihar increased to 7% during the second survey between August 21 and 26 and went up to 22.41% against the national average of 24% during the third survey between December 20 and 25, he added.

The recent survey assumes importance given the fact that this is the first such study since the commencement of the Covid-19 vaccination drive on January 16 this year.

It is also the first serosurvey after the second wave of Covid-19 ravaged the country in April and May, besides being the first to include children up to six years of age, believed to be the vulnerable age group in this pandemic.

The survey will give scientists a clue on the presence of antibodies among children as well as adults and health care givers. It will indicate the trend of spread and presence of the infection in the community and among health care workers.