The severity of the COVID-19 disease among people infected with the Delta variant of coronavirus was significantly lower among vaccinated individuals, a study by researchers from Hyderabad-based Centre for Cellular and Molecular Biology (CCMB) and AIG (Asian Institute of Gastroenterology) Hospitals found. “Severity of the disease (3.2% Vs 7.2%) and requirement of ventilatory support (2.8% Vs 5.9%) were significantly low in the vaccinated group despite the fact that these individuals had significantly higher age and risk factors,” the study said. The rate of mortality was found to be about 50% lower in fully vaccinated individuals having a breakthrough infection (despite completing 14 days after the second dose). A breakthrough infection is when a fully vaccinated person tests positive for coronavirus. However, mortality in people who received a single dose was similar to the unvaccinated group, the study found. Preliminary results suggest that both Covishield and Covaxin have comparable efficacies in reducing the severity (ICU requirement at the time of admission) and mortality among patients infected with the Delta variant, the study said.
The study, uploaded on the preprint server MedRxiv, observed clinical outcomes of 1,161 COVID-19 patients admitted to AIG Hospitals in Hyderabad between April 24 and May 31, 2021, at the height of the second wave of COVID-19 in India. Of these, 495 patients were vaccinated with a single or double dose of either Covishield or Covaxin, while 666 patients were unvaccinated. More than 90% of patients in both vaccinated and unvaccinated groups were found to have been infected with the Delta variant (B.1.617.2) of SARS-CoV-2. Patients in the vaccinated group were of significantly higher age, and a higher number in this group had comorbid conditions.
The study found a trend of increasing antibody levels and decreasing inflammatory markers in those who had received both vaccine doses compared with those who received a single dose. “Vaccinated individuals showed significantly higher neutralizing antibodies and lower inflammatory markers like serum Ferritin and Lactate Dehydrogenase, when compared to the unvaccinated group suggesting possible early neutralization of the virus and thereby prevention of aberrant inflammatory response,” the study found. Even within the vaccinated group, the study found that the neutralizing antibody response was significantly higher, and serum Ferritin levels were significantly lower in those who received Covishield (both doses) than those who received Covaxin (both doses). “However, no significant difference was seen in severity/mortality between both the groups,” the study said.
The study found no significant differences in the incidence of acute kidney injury (AKI), the requirement for renal replacement therapy (RRT) or thrombotic complications between vaccinated and unvaccinated groups. Commenting on the lower mortality among fully vaccinated patients, the study said that the results “become even more significant in the light of higher comorbidities and age in the vaccinated group. Majority of deceased in completely and partially vaccinated individuals had no/minimal antibody response which was comparable to unvaccinated individuals. Strategies targeting these non-responders to vaccination like additional booster doses or change of vaccine type need to be explored further.”
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