Delta variant could infect vaccinated & unvaccinated: Study

A new study by India’s top health research body has found that the Delta variant (B.1.617.2) has the potential to infect both vaccinated and unvaccinated people, though the study is based on a relatively small sample size.

“The prevalence of Delta variant was not different in vaccinated and unvaccinated people. B.1.617.2 has the potential to infect both the vaccinated and un-vaccinated individuals,” found the study by National Institute of Virology, Pune.

However, the study found that the proportion of patients progressing to severe illness and mortality was lower in the vaccinated group.


It said that the Delta variant was the dominant circulating strain and one of the primary drivers for the second wave of SARS-CoV-2 in India.

The experts involved in the study said that the progression of illness seems to be prevented by vaccination. “Therefore, non-pharmaceutical interventions must continue to slow down the transmission. Additionally, the pace and scale of vaccination has to be increased,” it said.

“We recruited majority of the vaccinated individuals visiting the triaging centre but only 5% of the unvaccinated individuals could be recruited due to logistics challenges. We could not follow up around 5% of the study participants,” it added.

The experts retrieved genomic sequences from 414 of the 539 samples. Median RT-PCR cycle threshold values were similar in the unvaccinated partially vaccinated and fully vaccinated groups.

B.1.617.2 (Delta variant) was the predominant variant in all groups: 72.4% in unvaccinated, 68.1% in partially vaccinated and 74.3% in fully vaccinated groups.

AY.1 (Delta plus variant) was isolated in five study participants. Of the five patients with AY.1 infection, one required hospitalisation for oxygen support and rest had mild disease.

Among the fully vaccinated, majority 85% (n = 96) had IgG antibody against SARS-CoV-2 S1-RBD whereas 63.9% (n = 154) partially vaccinated and 14.6% (n = 27) in the unvaccinated group were seropositive.