Monday, 24 January, 2022
HomeHealth1 in 6 people in Karnataka had Covid antibodies before second wave...

1 in 6 people in Karnataka had Covid antibodies before second wave struck, sero survey shows

Conducted from 25 January to 18 February, the survey found that the seroprevalence was highest in the 50-59 age group and lowest in the 18-29 group.

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Bengaluru: In the second round of a statewide sero survey in Karnataka conducted from 25 January to 18 February, before the second wave struck, the seroprevalence was found to be only at 15.6 per cent, which means that one in six people in the state had Covid-19 antibodies.

The low seroprevalence was due to antibody waning, a longitudinal substudy confirmed.

The survey, a pre-print of which was published Wednesday, found that the seroprevalence was highest among those between the ages of 50 and 59 years (16.8 per cent) and lowest among those between the ages of 18 years and 29 years (10.8 per cent).

While 15.4 per cent males were seropositive, 13.0 per cent of women were found with Covid antibodies.

Significantly, the survey found that unlike the first sero survey conducted in September 2020, seropositivity was higher in the rural population (15.4 per cent) when compared to the urban population (14 per cent).

“The state was far from attaining natural immunity during the survey and hence must step up vaccination coverage and enforce public health measures to prevent the spread of COVID-19,” said the study.

The survey also looked at the cases-to-infection ratio (CIR) and the infection fatality rate (IFR) across districts. Significantly, in districts like Belgaum, Kolar, Chamarajnagar, Mandya, Kodagu, Bagalkot, Vijayapura, Ramanagar, Mysuru, Chitradurga, Raichur, Davangere, Chikkaballapur and Gadag, the IFR was low while CIR was high.

“In anticipation of the third wave, districts with high CIR and low IFR should consider re-evaluating their testing strategies and death reporting. Vaccination coverage should be stepped up as is being done. A third sero survey is being planned and will provide valuable information. for vaccination prioritisation and revision of testing strategy,” Siva Athreya, a researcher on the study, told ThePrint.

In comments on the study, Giridhar R. Babu, an epidemiologist at the Public Health Foundation of India (PHFI), tweeted saying that the results from the sero survey had been used to update testing and surveillance strategies late March.


Also read: 505 paediatric Covid cases in Bengaluru in first 10 days of August, only 3 hospitalised


Survey specs

The survey saw 41,228 participants across 290 healthcare facilities in all 30 districts of Karnataka.

Researchers from the state’s Health Department, the Indian Institute of Science, the Indian Statistical Institute, the Indian Institute of Public Health, the National Institute of Mental Health and Neurosciences among others, undertook the study.

Of the 41,228 enrolled, valid IgG test outcomes were received from 40,030 participants.

The immunoglobulin G (IgG) antibodies are only found in an individual’s blood circulation in the recovery phase of the infection. Enzyme-linked immunosorbent assays (ELISA)-based test kits were used for the survey.

The researchers excluded those with a breakthrough infection (after the first round of the sero survey), those who had been vaccinated and those who had not given consent.

“Across risk-subcategories, pregnant women had the least total prevalence (8.9 per cent), while bus-conductors/auto-drivers (16.5 per cent), people with comorbidities (16.3 per cent), and the elderly (17.3 per cent) had higher prevalence,” found the survey.

Across districts, the prevalence was highest in Mysuru (33.6 per cent), Mandya (31.9 per cent), Kodagu (27.1 per cent), Chamarajanagar (22.6 per cent), and Kolar (20.8 per cent). In other districts, seroprevalence was reported below 15 per cent.


Also read: Difficult to ascertain oxygen-related deaths without probe, Sisodia writes to Mandaviya


 

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