The mutant variants of the coronavirus are making it difficult to ascertain how or when herd immunity might be achieved
Although recent research by icddr,b shows a higher rate of antibodies among people, health experts have said there is no way to believe that Bangladesh is near achieving herd immunity.
The world is no longer depending on herd immunity, but rather it is vaccination which is the means to develop immunity, they said at the virtual dissemination program of a study, “Driving factors of Covid-19 in Slums and Non-slum Areas of Dhaka and Chittagong”, conducted by icddr,b.
Speakers at the program said although more than a year had passed there was yet little knowledge about the virus and there was still no way to measure herd immunity for Covid-19.
Besides, several factors indicated that the country needed to conduct regular research as part of surveillance of the ongoing situation through scientific data, they added.
Epidemiologist Dr Abu Muhammad Zakir Hussain said achieving herd immunity would be difficult because of the emergence of new Covid-19 variants.
Herd immunity was related to the basic reproductive rate of the virus, and the reproductive rate of the Covid-19 variants active in the country was still unknown. So, there was no way to say if the country was nearing herd immunity or not, he added.
icddr,b Senior Scientist Dr Firdausi Qadri said despite over a year and a half of the pandemic having elapsed, scientists still could not understand the virus properly.
The emeritus scientist of the infectious disease division of the research organization said that previously it was seen that the coronavirus had a 2+ reproductivity rate while the current variant was said to have a 4++ reproductivity rate.
The new variants are proving to be more transmissible than previous ones, she added.
However, the icddr,b’s research shows that about 71% of people in and around the slums of Dhaka and 55% people in Chittagong have antibodies. This gives hope that antibodies are growing among people.
Another study in Sitakunda had also shown that people in the area had developed 60% seroprevalence positivity, commonly known as the presence of antibodies, added Dr Qadri.
Dr Qadri added: “Not everyone has the same level of antibodies. So, the vaccination program needs to continue with whatever vaccines we have.”
A member of the National Immunization Technical Advisory Group (NITAG), Prof Mahmudur Rahman, said the calculation of herd immunity differed from disease to disease.
Epidemiologists generally accepted that if 88% of the total population become immune to an infectious virus, herd immunity had developed there, he added.
The World Health Organization (WHO) initially said it to be 70%, but it has already changed its stance and global scientists are not depending on the herd immunity strategy anymore.
To determine what strategy Bangladesh needed to adopt amid the ever changing situation, continuation of more similar research was needed, advised the professor.