The highly contagious Delta Covid variant infected more than 80 per cent people in India during the devastating second wave of the pandemic, affecting even those who took at least one vaccine dose, revealed a study by the Indian Council of Medical Research (ICMR).However, the study suggests that vaccination does provide a reduction in hospital admission and mortality, the ICMR said.The study conducted a clinical characterisation and genomic analysis of 677 Covid-19 positive cases. Of these 71 had taken the Covaxin vaccine, 604 got the Covishield vaccine, while two took the Sinopharm vaccine. The samples were collected from 17 states and Union Territories.A majority (86.09 per cent) of the infections were caused by the Delta variant (B16172). While 9.8 per cent of the positive Covid-19 cases required hospitalisation, only 0.4 per cent of the infected persons died.At the same time 482 cases (71 per cent) were symptomatic with one or more symptoms while 29 per cent were asymptomatic. Of the samples, fever (69 per cent) was found to be the most consistent symptom followed by body ache, headache and nausea (56 per cent), cough (45 per cent), sore throat (37 per cent), loss of smell and taste (22 per cent), diarrhoea (6 per cent), breathlessness (6 per cent) and 1 per cent had ocular irritation and redness, ICMR said.The Delta variant has spread to more than 111 countries, according to the World Health Organization. The health body expects it to soon be the dominant Covid-19 strain circulating worldwide and cause a third wave of the coronavirus.According to the Health Ministry, both Covaxin and Covishield are effective against the Delta Covid variant.Covaxin is developed and manufactured by Hyderabad-based Bharat Biotech, while Covishield is developed by Astra-Zeneca and the University of Oxford, and manufactured by Serum Institute of India, Pune.