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Covid-19 recovered people who showed a faster antibody response to the Covishield vaccine: study | India News

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NEW DELHI: Those who have recovered from Covid-19 respond faster to the Covishield vaccine and reach high levels of antibodies, says a study, raising hopes that they do not need a second dose and therefore help to scale the crown immunization coverage of India.
The study on the immune response to Covishield was carried out by researchers from the CSIR-Institute of Genomics and Integrative Biology (IGIB) in New Delhi, Max Super Specialty Hospital and the Institute of Endocrinology, Diabetes and Metabolism, as well as the Academy of Scientific and Innovative Research. (AcSIR) in Ghaziabad.
Covishield is inducing a strong immune response. Those who are seropositive at the start of the study respond faster and reach higher levels of antibodies, CSIR-IGIB director Anurag Agrawal, one of the study’s authors, told PTI. Seropositivity is an indicator of the presence of the virus in serum or evidence of previous exposure to it.
The Oxford-AstraZeneca Covid 19 vaccine, or ChAdOx, is an important part of the global launch of the vaccine. Covishield, a version manufactured locally by the Serum Institute of India in Pune, is one of two vaccines along with the indigenous Covaxin, from the Hyderabad-based company Bharat Biotech, approved for use in the country.
The study, which involved 135 healthcare workers, was specific to Covishield.
In the vaccine, scientists have engineered a version of adenoviruses that infect chimpanzees to carry the gene responsible for the spike protein of the new coronavirus, which it uses to enter human cells. Adenoviruses are common viruses that cause a wide range of illnesses and symptoms such as colds, sore throat, bronchitis, pneumonia, diarrhea.
Using two doses of ChAdOx, administered four weeks apart, human cells train the immune system to recognize and retain the memory of the virus spike protein to neutralize it and prevent infection when the actual coronavirus infects people. The new study, published online in the medRxiv preprint repository and not peer-reviewed, estimated the effectiveness of the first dose of Covishield in generating an antibody response.
The researchers measured SARS-CoV-2 antibodies directed against the spike protein in the 135 healthcare workers given Covishield. Antibody levels were measured quantitatively at 0, 7, 14, 28 days after the first dose of the vaccine, Agrawal said.
The team found differences in antibody levels between immunized individuals who were already HIV-positive compared to those who were not. In 44 people who had already developed antibodies to SARS-CoV-2 on day 0 (before immunization), the antibody response was significantly higher, with the maximum increase seen between days 0 and 7, the researchers said.
In contrast, the seronegative group of 91 people began to develop an antibody response only after 14 days or more. Three seronegative individuals did not develop an antibody response even on day 28 of vaccination, the researchers said. The average 28-day antibody response in seronegative subjects was similar to that of seropositive subjects at the start of the study (day 0), and was on an upward trajectory, they said. Our data suggest that ChAdOx1 is highly immunogenic, particularly when a prior antibody response against SARS CoV2 is established, the study authors noted.
Given the high background seropositivity in India, this may be helpful in determining the optimal timing of the second dose during mass immunization within the limitations of vaccine supply and administration, they said.
Reacting to the findings, immunologist Vineeta Bal, who was not involved in the research, said the study’s sample size is small. Although a single dose of Covishield is not enough to trigger an adequate immune response in everyone, necessitating a booster dose, it is sufficient in people who are already exposed to SARS-CoV2, he noted.
They may not need the second dose and therefore those doses can be saved to increase coverage, explained the scientist from the Indian Institute of Education and Scientific Research in Pune. This number, the immunologist said, could reach 30 percent of the entire population based on the results of sporadic serosurveys available in the public domain from India. Therefore, it makes sense to perform a random check for pre-existing antibodies before vaccination, he added.
Agrawal said the study supports the effectiveness of India’s vaccination program and helps determine the timing of the second dose. At 28 days, there was a good immune response in almost all of our participants. This needs further confirmation and may lengthen our window for the second dose, especially in communities with high rates of seropositivity, he explained. One caveat in the data, Bal noted, is that it is not mentioned whether preimmune individuals were asymptomatic RT-PCR positive or had the disease.
A wide range of antibody titers are seen and it would have been nice to establish some correlation between disease severity and immune response, even if it was only a weak association due to limited numbers, he added. Antibody titer is a test that detects the presence and quantitatively measures antibodies in a person’s blood.
On Monday, India opened its vaccination program to all people over the age of 60 and people aged 45 to 59 suffering from specific comorbidities.

Times of India

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