ICMR study in Chennai shows Delta variant infects both vacci
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An Indian Council of Medical Research (ICMR) study conducted in Chennai has found that the Delta variant of the Covid-19 virus has the potential to infect both vaccinated and unvaccinated people, but it reduces mortality among the former group. The study was approved by the Institutional Ethics Committee of ICMR-National Institute of Epidemiology, Chennai.

The study findings indicate that the prevalence of the Delta variant or B.1.617.2 was not different between the vaccinated and unvaccinated groups. The high transmissible Delta variant is the dominant strain circulating across the world and is one of the primary drivers for the second wave of SARS-CoV-2 in India.

Jeromie Thangaraj, a scientist at the National Institute of Epidemiology who was involved in the study said that since the sample size was low, they did not include re-infections as it was very few and have not further classified whether those who were infected post-vaccination had taken Covishield or Covaxin. “But the proportion of patients progressing to severe illness and mortality was lower in the vaccinated group which is the case globally,” said Jeromie.

Of the 3,790 people who visited the triage centres between the first week of May, 373 reported receiving at least one dose of vaccine 14 days prior to their Covid-19 positive diagnosis. The remaining 3,417 were unvaccinated. The study enrolled 354 (94.9%) of the 373 in the vaccinated group. Of this 241 people had taken one dose or were partially vaccinated and 113 had taken two doses or were fully vaccinated. As many as 185 (5.4%) of the 3417 unvaccinated individuals were included in the study. The median age of the individuals who were unvaccinated, partially vaccinated and fully vaccinated were 47 years, 53 years and 54 years respectively.

After retrieving genomic sequences from 414 of the 539 samples it was found that the delta variant was the predominant variant of concern in Chennai. About 72.4% in the unvaccinated group and 68% and 74% among the partially and fully vaccinated groups were found. Among the fully vaccinated, a majority that is 85% had IgG antibodies against SARS-CoV-2 whereas 63.9% were partially vaccinated and 14.6% in the unvaccinated group were seropositive. “We also found the delta plus variant in five participants,” said Thangaraj. One out of the five infected with delta plus (AY.1) required hospitalisation with oxygen support but the rest had mild disease.

Dr K Kolandaswamy, the former director of the directorate of public health in Tamil Nadu said that the objective for vaccination is threefold prevention: from infection, from the severity of disease and mortality. “The study isn’t able to measure how much prevention from infection has been achieved but it does clearly indicate that the other two objectives are working,” Kolandaswamy said.