Both the alpha and delta variants are highly contagious, with delta being nearly twice as transmissible as the original strain of SARS-CoV-2. The rapid rise in cases in India is attributed to the high viral load – the amount of virus infecting a person – of delta, which is about 1,000 times higher than other strains. This resulted in widespread infections among household members with rates as as high as 80% to 100%.
How many of India’s 1.3 billion people have been infected?
In the aftermath of the second wave from roughly April to June, the Indian Council of Medical Research conducted the fourth round of a national sero-survey in June and July 2021 to test for antibodies in blood samples from residents across 70 districts of 21 states. The overall sero-prevalence was 67.6%, a huge increase from 24.1% recorded in the third round from December, 2020 to January, 2021. The presence of antibodies indicates that a person has either been exposed to the coronavirus or has been vaccinated.
Sero-positivity among children was 57.2% in those aged 6-9 years and 61.6% among those who are 10-17 years old. Experts believe that there is not much scientific evidence that children would be disproportionately vulnerable in a third wave. The government, however, anticipates the possibility of intermittent surges in the number of cases and prepared operational guidelines for children and adolescents in preparation for a third wave. Seroprevalence among those above 45 years was 77.6% and 66.7% among younger adults, indicating the effect of vaccination as well as infections.
The coronavirus had spread through the entire country; seroprevalence among the rural population (66.5%) was only slightly lower than in urban counterparts. A wide range of interstate differences have emerged, from a low of 44.4% in Kerala to 79% in Madhya Pradesh.
The extent of undercount – the difference between estimated cases (based on seroprevalence) and actual cases detected by RT-PCR and rapid antigen tests – is particularly worrying. Nationally, the system missed 33 cases for every one detected.
What are the prospects for the weeks and months ahead?
COVID-19 vaccination in India has been marked by both inequity and hesitancy; negotiating both will be crucial in the weeks ahead.
The range of vulnerabilities have included rural and remote locations and a lack of access to the internet; a gender divide has emerged too with more men being vaccinated than women. As vaccination progresses with underlying inequities, the phenomenon of “patchwork vaccination” emerges – pockets that are highly vaccinated and adjacent to places or communities with low coverage. The communities with low coverage are vulnerable to hyperlocal outbreaks.
Most economic activities have resumed, and the education and entertainment sectors are opening up too. A joint statement on June 6, 2021, issued by the public health associations in India urged that district-level sero-surveys be undertaken by the state or federal health services to enable a more granular understanding of the epidemiologic context to enable planning. While this was accepted in principle, such systematic surveys have yet to be rolled out.
The World Health Organization advises that public health and social measures in the context of COVID-19 be guided by local transmission dynamics. Planning at the district level in India shall be crucial in the journey ahead.
ABOUT THE AUTHOR
Dr. Rajib Dasgupta graduated in Medicine from the University of Calcutta in 1989 and obtained his Masters and PhD in Community Health from Jawaharlal Nehru University, New Delhi, India. He served a decade (1993-2003) with the Epidemiology Division of the Municipal Corporation of Delhi and dealt with the epidemics of Cholera O139, Plague, Dengue Hemorrhagic Fever and SARS. He joined JNU in 2003 where he is currently Professor and Chairperson at the Center of Social Medicine & Community Health. He was Fulbright Nehru Senior Research Fellow and Visiting Associate Professor at the Department of International Health, Johns Hopkins Bloomberg School of Public Health during 2010-11 and Key Technology Partner Visiting Fellow 2016 at the Australian Research Centre in Complementary and Integrative Medicine, University of Technology Sydney. He is closely engaged with the Indian Council of Medical Research (ICMR), the National Certification Committee for Polio Eradication (NCCPE) and the National Health Mission as well as several other key national health programs and evaluations. He has been a consultant to UNICEF, World Bank and Save the Children. Widely published in national and international journals, he has also been Managing Editor of the Indian Journal of Community Medicine (2012-14) and Guest Editor of the COVID-19 Special Issue of the Indian Journal of PUblic Health (2020).