87% breakthrough cases test +ve for Delta variant, finds NIV study

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.
Three patients, who had taken both the shots, died, but their age and existing medical conditions were not mentioned. Over 20% of these patients had comorbidities such as diabetes, hyptertension or chronic lung, heart or kidney conditions.
The genomic analysis showed the Delta variant’s presence in the majority of the samples, but there also were other variants such as Alpha, Kappa, Delta AY.1 (known as the Delta-plus variant in samples from MP and Rajasthan) and Delta AY.2.
The occurrence of Covid in vaccinated people is called a ‘breakthrough infection.’ The NIV study, which is in the preprint stage of publication, proves that the Delta variant -- first isolated in Vidarbha in October 2020 and now acknowledged as the cause for the massive second wave -- caused breakthrough infections.
Dr Yadav said, “At the moment, the Delta variant is causing infections throughout the world, but the most important point of our study is that vaccination offers more than 99% protection against death even in the presence of the highly transmissible and more virulent Delta strain.”
While 53 samples for the study, conducted between March and June, were collected from Maharashtra, the highest number was 181 from Karnataka and the lowest number was 10, from West Bengal. Genetic sequencing was performed on each positive sample to find the Delta variant.
“This study indicated that a majority of the clinical cases in the breakthrough were infected with the Delta variant and only 9.8% cases required hospitalization, while fatality was observed in only 0.4% cases. This clearly suggests that the vaccination does provide reduction in hospital admission and mortality,” concluded the study.
Most patients in this study were young -- the median age was 44 (31-56), more were men (65.1%) and 71% of them were symptomatic, with one or more symptoms. Fever (69%) was the most common symptom, followed by bodyache, including headache and nausea (56%), cough (45%) and sore throat (37%).
The researchers said breakthrough Covid-19 infections have been reported from various countries. “It appears the current Covid-19 vaccines are disease-modifying in nature wherein mild or less severe infections are expected to occur in vaccinated individuals,” said the study. Vaccination prevents severe disease, hospitalization and death, as is being seen in the UK, Israel and Canada.
The NIV doctors said continuous monitoring of breakthrough infections is important. “Such monitoring will help us understand the need to adequately tweak the available vaccines and also develop new vaccines with enhanced potential to protect against variant strains of SARS-CoV-2,” said Dr Yadav