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Even though Bangladesh logged 15,61,463 Covid-19 cases as of Friday, experts believe around 70 per cent population of the country may have contracted the virus and developed natural antibodies.
Some experts think that the country is close to reaching the herd immunity threshold while some others say a comprehensive serosurveillance report is necessary to reach a conclusion over it.
They all, however, viewed that it is necessary to inoculate around 70-80 per cent of people of the country to attain herd protection against the coronavirus as any virulent new variant like Delta can emerge and dodge people’s natural immune protection.
Herd immunity is a concept based on the body’s immune resistance to the spread of a deadly disease (bacterial or viral infection) and it can be obtained in two ways -- naturally through infections of the majority of the population and artificially through vaccinating around 80 per cent of the population of a country.
Official data on infection, vaccination
As per the data of the Directorate General of Health Services (DGHS), Bangladesh reported 15,61,463 cases till Friday while the positivity rate was 2.77. The daily-case positivity rate in the country remained below 5 percent for over last two weeks.
According to the DGHS, a total of 35,829,418 people received the first dose of vaccines while 17,795,120 ones both doses as of October 7.
The country has so far collected 64,568,420 doses of AstraZeneca, Pfizer, Moderna and Sinopharm vaccines.
Meanwhile, Health Minister Zahid Maleque on Saturday said around five crore people have already been vaccinated while 50 per cent will be brought under the vaccination by December next.
He said they also have a plan to vaccinate 70-80 per cent people of the country by March next year.
Debate over antibody, herd immunity
Based on some studies on samples collected from both symptomatic and asymptomatic Covid positive individuals, Ramon Magsaysay Award-winning Bangladeshi scientist Dr Firdausi Qadri said 60-70 per cent people of Bangladesh have gained some types of antibodies against Covid-19.
She said the Covid infection rate declined significantly in the country due to the development of Covid-19 resistant herd immunity.
Dr Qadri, an emeritus scientist at icddr,b, however, said herd immunity is not only dependent on infection-related exposure and seroprevalence as it is also dependent on vaccination of at least 70 per cent population. “So, with the exposure and infection-related seropositivity, vaccination status and rates, in a country are related to herd immunity and herd protection,” she observed.
Renowned scientist and Gono Bishwabidyala’s microbiology department Prof Dr Bijon Kumar Sil thinks Bangladesh has almost reached the herd immunity threshold against Covid through natural infection.
“Though Dr Firdausi Qadri said 60-70 per cent people gained antibodies, I personally think it’s over 80 per cent. Otherwise, the Delta variant wouldn’t have come under control. But if we can carry out any scientific research with representative samples, then we’ll get a clear idea about the percentage of our population with antibodies,” he said.
Dr Bijon said it is not possible to contain a virulent variant like Delta without antibodies among the majority of people.
“As the current Covid infection rate has come down to below three per cent, it’s an indication that over 80 per cent people have now antibodies in Bangladesh.”
Even though, he said vaccination is necessary to boost up the antibody as it declines after a few months. “If we inoculate and at least our 80 per cent people, then we may not witness any major outbreak of the virus even if any new variant like the Delta one emerged.”
Prof Muzaherul Huq, a former adviser to WHO South-East Asia region, said Bangladesh is moving towards herd immunity. “But we still couldn’t attain the herd immunity though many experts believed immunity developed among around 60-70 per cent people through contracting the virus.”
He said the actual herd immunity can be achieved only by vaccinating 80 per cent of the population.
Public health expert MH Chowdhury (Lenin), chairman of the medicine department at the Health and Hope Hospital, said there is no available scientific evidence and serosurveillance report that suggests
Bangladesh reached the heard immunity against Covid.
“We shouldn’t focus on herd immunity now. As the virus now remains under control, we should make a target to eliminate it by vaccinating most of the population as early as possible,” he said.
