Second Covid wave in Delhi shows reaching herd immunity difficult with Delta: Study

In June, the corresponding number was 88.5 per cent, suggesting very high infection rates during the second wave. Among 91 subjects with prior infection before Delta, about one-quarter (27.5 per cent) showed increased levels of antibodies, providing evidence of reinfection.When the team sequenced all the samples of vaccination-breakthrough cases at a single centre over the period of the study, they found that among 24 reported cases, Delta was seven-fold more likely to lead to vaccination breakthroughs than non-Delta lineages.Since the first case of Covid-19 was detected in Delhi in March 2020, the city had experienced multiple outbreaks, in June, September and November 2020.In November 2020, the capital city had almost 9,000 cases daily, but it declined steadily between December 2020 and March 2021. However, the situation reversed dramatically in April 2021, going from approximately 2,000 daily cases to 20,000 between March 31 and April 1.



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