The Oxford-AstraZeneca (Covishield) vaccine has produced a strong immune response among the recipients in Bangladesh, according to a study carried by scientists.
In an interim analysis, scientists at International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) and the Institute of Epidemiology, Disease Control and Research (IEDCR) with support from the United States Agency for International Development (USAID) measured levels of SARS-CoV-2 IgG antibodies in the blood of 120 participants before vaccination and then at one and two months after vaccination with the first dose of the Covishield vaccine.The vaccine recipients were aged between 40-73 years of age (average age 49 years) comprised of individuals with or without history of prior Covid-19 and from Dhaka city.
It was found that one month after vaccination, 92 per cent of the people who received the first dose of vaccine have high immune response (geometric mean concentration of antibody against the virus 2,586 ng/ml) and 97 per cent of the people have even higher immune response (GMT 3,460 ng/ml) two months after the first dose of vaccination.
Cut-off for a positive IgG antibody response to the spike protein of SARS-CoV-2 was set at 500 ng/ml using 355 serum samples collected prior to the onset of the pandemic.
Some 46 participants (average age 48 years) with previous RT-PCR confirmed SARS-CoV-2 infection history (between April 2020 and January 2021) were also included in the analysis.
The participants who had a previous infection with SARS-CoV-2 (one month or earlier before vaccination) showed more robust response after receiving the first dose of vaccine.
A fourfold higher magnitude of antibody response was seen among these participants at two months after receiving the first dose of vaccine.Dr Firdausi Qadri, senior scientist at the icddr,b who is leading the study from icddr,b, said in the analysis, “We now know that the Covishield vaccine induces robust immune response in Bangladeshi adults which is indeed a great news. However, we’ll continue working on evaluating the neutralising ability of the antibody as well as the T and B cell responses. We’ll also continue assessing the effectiveness of the vaccine in our setting.”
IEDCR Director Prof Dr Tahmina Shirin said, “Our analysis confirmed that the vaccine works and people should get it when their turn comes. However, everyone should continue wearing face mask and maintain physical distancing along with personal hand hygiene to keep themselves and their loved ones protected from Covid-19.”
icddr,b and IEDCR have started a large-scale study at 12 sites in eight divisions across Bangladesh that will involve about 6,300 participants who will complete their full course of vaccination.
The participants will be followed up for two years in a longitudinal design for assessing antibody responses after vaccination (day 0 and months 1, 2, 3, 6, 12, 18, and 24) to determine the longevity of antibody response.
The Covishield vaccine is developed by Oxford University vaccine group, marketed by AstraZeneca and manufactured by the Serum Institute of India.