Representative image MUMBAI/PUNE: In the largest study done so far in India to understand why people got Covid-19 despite taking one or two vaccine shots, scientists from Pune-based National Institute of Virology (NIV) found a simple answer: B.1.617.2 (Delta variant). Genomic analysis found Delta in 87% of the 677 throat and nasal swabs of patients from 17 states and UTs. While 592 of them had taken two doses, 85 had taken only one dose before getting infected with the SARS2 virus. The study, led by director Dr Priya Abraham and senior scientists Dr Pragya Yadav, also found that less than 10% of the 677 patients needed hospitalisation, alluding to the vaccine’s effectiveness in preventing a severe infection.