Covaxin, Covishield not immune to Delta, Alpha variants: Study

A study conducted by AIIMS, New Delhi found breakthrough infection caused by the two variants, but vaccines remain relevant.

Covaxin, Covishield not immune to Delta, Alpha variants: Study
Variants of concern B.1.617.2 and B.1.1.7 were responsible for cases surge in April-May 2021 in Delhi. (Photo credit: AFP)

New Delhi: The Delta (B.1.617.2) and Alpha (B.1.1.7) variant of the coronavirus are capable of causing breakthrough infection in fully and partially vaccinated individuals, a study by the All-India Institute of Medical Sciences (AIIMS), New Delhi has found.

The study was conducted on 63 subjects drawn as part of routine testing for patients reporting to the Emergency Department of the hospital with symptoms of high-grade fever, shortness of breath and headache.

Of the 63 samples, 57.10 percent or 36 patients were found to be infected with SARS-CoV-2 or coronavirus lineages that cause COVID-19.

Breakthrough infections were found in 52.80 percent or 19 patients who had been administered both doses and 47.2 percent or 17 patients who completed only a single dose, with the Delta variant being the dominant variant.

Fully- and partially-vaccinated patients

“SARS-CoV-2 lineages could be assigned for a total of 36 (57.1%) samples, 19 (52.8%) in patients who completed both doses and 17 (47.2%) in patients who completed only a single dose,” the paper says.

“B.1.617.2 was found to be the predominant lineage with 23 samples (63.9%) out of which 12 were in fully vaccinated and 11 in partially vaccinated groups. (11.1%) and 1 (2.8%) samples were assigned the lineages B.1.617.1 and B.1.1.7 respectively,” the study further found.

According to the paper, the majority of the breakthrough infections were caused by the variants of concern Delta (B.1.617.2) and Alpha (B.1.1.7), but the proportions were not significantly different when compared to their spread in the population of Delhi during this period with high community transmission.

Variants of concern B.1.617.2 and B.1.1.7 were responsible for cases surge in April-May 2021 in Delhi.

Sample may not be representative

Speaking with TV9 News, Dr E Venkata Rao, Principal Investigator of the Covaxin trials at the Institute of Medical Sciences and SUM Hospital, Bhubaneswar, Odisha, said the sample should include both vaccinated and non-vaccinated group.

“Since all are patients who have visited the hospital, this may not be representative of the entire population. The sample size should be scientifically chosen based on that any concrete conclusion can be made.”

Of the 63 patients studied 36 patients received two doses, while 27 received one dose of vaccine.

Ten patients received the Covishield vaccine (AZD1222), while 53 received indigenous Covaxin (BBV152).

Covid infections in vaccinated people once again raise the issue of efficacy of vaccines against the mutations of coronavirus or variants.

Risk from variants

Dr Sushil T Jain, an Immunologist and Pulmonologist at Saifee Hospital in Mumbai, says the Delta (B.1.617.2) variant is the major strain behind the second wave of pandemic in India.

“The study does suggest that the Delta variant is least affected by the vaccine and we have also observed so at our hospital.”

Medical experts say the fight against the virus is done by cell immunity and not by antibodies so much. People get infected between doses despite being immunised as they stop taking proper preventive measures to allow a robust immune response to set in.

Dr Jain says if the immunity against a variant is low new waves driven by the variant can occur in the future.

“We need to study the variants well to develop more effective vaccines. In the UK as well, the dominant variant now is the Delta variant.

We have to study the impact of vaccines in countries where large populations have been immunised. These studies can provide a good insight into how the vaccines prevent infection or transmission.”

The paper says recent evidence from the United States suggests vaccine breakthrough infections to be approximately 0.01per cent in fully vaccinated populations.

Current vaccines remain crucial

Despite the breakthrough infections, the role of the current vaccines is to reduce the severity of the disease and deaths among those who get infected.

This means the need for people to get hospitalised is reduced and, hence, the burden on the health infrastructure.

Institute of Genomics and Integrative Biology (IGIB) and the Centre for Cellular and Molecular Biology (CCMB) in separate studied conducted in April confirmed that both Covishield and Covaxin have efficacy against the B.1.617 variant.

“Initial positive neutralization studies of B.1.617, with both post-Covaxin or Covishield sera, are correlatable with milder disease during post-vaccination breakthrough infections. This is a positive while we get quantitative data for better understanding of infection protection,” Anurag Agrawal, the Director of IGIB wrote on Twitter citing preliminary results of the study on April 27.

The AIIMS study that is yet to be peer-reviewed also indicates is that despite getting immunised one cannot stop practicing social distancing, wearing of masks and washing hands with soap and water for 20 seconds.

As soon as Covid-appropriate behaviour is compromised, the risk of emergence of new variants and waves raises its head.