‘It is a misconception to think we have developed herd immunity’

The International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) has recently carried out a study where they found that 71% slum dwellers in Dhaka and 55% slum dwellers in Chattogram have developed coronavirus antibodies. 

There is a concept that the working class who live in densely populated areas do not contract Covid-19 and have higher antibodies. Studies are being done at home and abroad to see if that concept is real. In the past also, similar studies were carried out. 

This study conclusively proves that in our country, low-income groups are also being infected with Covid-19. The percentage of infections is higher among people who live in slum areas, presumably because they have to be at their workplaces for a longer period. 

Many of the slum dwellers did not know that they have been infected with the coronavirus. They may have been exposed to mild symptoms and did not test or understand the symptoms. They did not go to hospitals, largely because they are young and are employed in hard labour. 

They did not become severely ill which is why they did not have to go to hospital. Nonetheless, they did get infected with the virus, which is that they have developed antibodies. 

The first thing we need to realise is that antibodies do not exist in body all the time. They had antibodies at the time the samples were collected. People who become severely ill have long-lasting antibodies than those who had mild or no symptoms.  

Therefore, it would be a misconception to believe that since they have antibodies, we have achieved herd immunity. As antibodies are not permanent, many studies are being conducted at home and abroad globally to see how many days' antibodies survive after vaccination. Natural antibodies probably last even less. 

Secondly, these antibodies were developed before the Delta variant of the virus arrived, therefore they are unlike to help in resisting the current strain of infection.

It is very important to remember that we should not entertain any false hopes about 71 per cent slum dwellers having developed resistance power. 

Following the publication of a previous study, we saw some people draw a conclusion that most of the people in Dhaka city have been exposed to Covid-19 and there was no chance of more infection. That conception even confused our policymakers too. As a result, in last March and April, the infection curve went upward fast and lots of people died.

We have to interpret the study very cautiously. The antibodies were found only in the selected slum areas, not in the whole city. The study is not representative of the whole city. The infection rate among low-income people is higher because of their lifestyle and work environment.  

Those who have symptoms will have to get tested so that other members of the family do not get infected with Covid-19. 

When the second wave came following the Eid, we thought the curve would come down soon. However, we are into the third wave now. If the daily infection crosses 4,000 and the infection rate crosses more than 20 per cent, we can easily say that it is the third wave. 

The curve of the current wave has already reached the height of the first wave. 

Meanwhile, the initiative to lockdown other places to save Dhaka from infection is a discriminatory approach. The government's responsibility is not to save Dhaka only. The government's responsibility is to save people across the country. The government should bring down the infection rate to less than 10 per cent before Eid. 

There is a risk of rising infection on the eve of Eid because some people want to go to their hometown and at the same time, some people who rear livestock will come to Dhaka to sell them. So yes, cutting off Dhaka from other parts of the country will help keep the infection rate lower. 

The government should restrict movement in places where the infection rate is over 10 per cent. If the government enforces lockdown rigorously, the infection rate will come down within two weeks.    

Dr M Mushtaq Hussain is the adviser to the Institute of Epidemiology, Disease Control and Research (IEDCR)