Higher COVID-19 seropositivity observed among residents in Dhaka and Chattogram

22 JUN 2021

Today, scientists at icddr,b have virtually disseminated the findings of a recently completed study that evaluated the extent of spread of SARS-CoV-2 in individuals residing in the slum and non-slum communities in Dhaka and Chattogram. The study also analysed different factors associated with seropositivity, having the presence of antibodies against SARS-CoV-2 in blood serum.It was supported by UNFPA and the Foreign, Commonwealth and Development Office (FCDO), UK. Dr. Rubhana Raqib, Senior Scientist and Dr Abdur Razzaque, Emeritus Scientist at icddr,b were the principal investigators of the study.

The main objective of the study was to ascertain the seroprevalence of COVID-19 among slum and non-slum dwellers and identify probable risk factors, which were examined included presence of other respiratory viruses, nutritional factors (Vitamin D, Zinc, Selenium), and immunological factors. It was a cross-sectional study involving 3,220 people residing in slums and adjacent non-slum areas in Dhaka and Chattogram cities. It took place between October 2020 and February 2021. Household-level interviews, blood pressure and anthropometric measurements, and blood samples were collected. SARS-CoV-2 serology was assessed by the Roche Elecsys® Anti-SARS-CoV-2 immunoassay (approved for emergency use by FDA).   

Dr. Rubhana Raqib presented the major findings of the study, these are -

• The overall adjusted seroprevalence among 3,220 participants was 68% with higher seropositivity in Dhaka (71%) than in Chattogram (55%). The seropositivity was higher in adults (70%) than in children (65.5%). The presence of SARS-CoV-2 antibodies was higher in females (70.6%) than in males (66%). Among the participants having antibodies (n=2,209), only 35.5% were estimated to have some/mild symptoms of COVID-19.
• Higher seroprevalence was found in individuals with fewer years of education, diabetes, overweight, and hypertension.
• Lower seroprevalence was found in individuals who frequently washed hands, did not put fingers on the face/ in the nose, have been vaccinated with BCG, carried out moderate physical activities.
• Individuals having antibodies appear to have higher serum zinc levels compared to seronegative people.This may be related to mild disease or asymptomatic infection in our study population.
• Inadequate vitamin D status did not show any impact on seropositivity.There was high rate of vitamin D insufficiency (> 84.6%) in the population.

The findings concluded that overall seropositivity was slightly higher in Dhaka than in Chittagong. The estimated SARS-CoV-2 antibody seroprevalence was higher in slums than in the adjacent low-to-middle-income non-slum areas.Preventive measure such as frequent washing of hands had a beneficial impact on infection. Other driving factors associated with seropositivity included overweight, diabetes and hypertension. Being engaged in moderate physical activity were associated with a lower probability of seropositivity.The study found a high prevalence (85%) of Vitamin D insufficiency among participants.

Dr. Tahmeed Ahmed, Executive Director at icddr,b; Dr Firdausi Qadri, Senior Scientist at icddr,b; Professor Dr Mahmudur Rahman, Member of the National Technical Advisory Committee on COVID-19 and Former Director, IEDCR; Dr. A. S. M. Alamgir, Chief Scientific Officer at IEDCR and Dr. Shehlina Ahmed, FCDO spoke on the occasion. Representatives from different government agencies, development partners, NGOs and media were also present at the dissemination seminar.

The virtual seminar was organised by the advocacy partner Bangladesh Health Watch.