Fewer hopsitalisations (9.8%) and deaths (0.4%) were reported in people having experienced breakthrough Coronavirus disease (Covid-19) infection after two doses of vaccine, highlighting the fact that vaccination does reduce hospital admission and mortality, according to a pre-print study.
The nationwide study conducted by the Indian Council of Medical Research (ICMR) during the peak of second wave between April and June 2021, is likely the largest and first nation-wide study of post-vaccination breakthrough infections from India with 677 clinical samples.
The vaccines used for the study were Bharat Biotech’s Covaxin and Serum Institute of India’s Oxford-AstraZeneca vaccine that it is locally producing as Covishield.
““During March to June 2021, India has experienced a deadly second wave of Covid-19 with an increased number of post-vaccination breakthrough infections reported across the country. To understand the possible reason of these breakthroughs, we collected 677 clinical samples (throat swab/ nasal swabs) of individuals who had received two doses (n=592) and one dose (n=85) of vaccines (Covishield and Covaxin,) and tested positive for Covid-19, from 17 states/Union Territories of country,” said the study paper.
These cases were telephonically interviewed and clinical data was analysed. Out of 677 cases included in this study, 593 were the clinical samples from breakthrough and 84 had infection after one dose.
A total of 482 cases (71%) were symptomatic with one or more symptoms, while 29% had asymptomatic SARS-CoV-2 infection. Fever (69%) was the most consistent presentation followed by body ache including headache and nausea (56%), cough (45%), sore throat (37%), loss of smell and taste (22%), diarrhoea (6%), breathlessness (6%) and 1% had ocular irritation and redness.
“This study indicated that majority of the clinical cases in the breakthrough were infected with the Delta variant and only 9.8% cases required hospitalisation while fatality was observed in only 0.4% cases. This clearly suggests that the vaccination does provide reduction in hospital admission and mortality,” finds the study.
The aim of conducting the study was to allay fears regarding vaccination with growing questioning of the protection offered by vaccines following the emergence of variants of concern and reduced real world effectiveness of certain candidate vaccines against these variants.
The Indian Council of Medical Research -Department of Health Research (ICMR-DHR) utilised network of Viral Research and Diagnostic Laboratories (VRDLs) to track breakthrough infections .
Breakthrough cases are defined as the detection of SARS-CoV-2 RNA or antigen in a respiratory sample collected from a person 14 days after receipt of all recommended doses of a Covid-19 vaccine.
“It was observed that southern, western, eastern and north-western regions of India predominantly reported breakthrough infections from mainly Delta and then Kappa variant of SARS-CoV-2. The northern and central regions reported such infections due to Alpha, Delta and Kappa variants; however, cases due to Alpha variant predominated in the northern region. The overall majority (86.09%) of the breakthrough infections were caused by the Delta variant (B.1.617.2) of SARS-CoV-2 in different regions of India except for the northern region where the Alpha variant predominated,” the researchers found in the study.