Noman Mosharef :
Pursuing herd immunity has been touted as a possible strategy in poor countries with young populations. This controversial approach, which was recently discarded by the United Kingdom, relies on a majority of the population (60 per cent to 80 per cent) gaining immunity or resistance to the virus by becoming infected and then recovering.
While this is a common approach underlying mass vaccination campaigns for diseases like measles-which rely on safe and tested vaccines-trying it with a deadly, new, and untreatable disease is a massive risk. In its cruellest form, it is a version of survival of the fittest.
So far in Bangladesh, steps like ‘shutdown’ have been taken to deal with the coronavirus situation. But Professor Nazrul Islam, one of the country’s leading virologists, told the media that the pattern or graph of the infection showed that there was no choice but to wait until “herd immunity” is arrived as it is not possible to impose a strict lockdown in Bangladesh to contain the virus.
He said this when the government of Bangladesh is easing restrictions and reopening factories, shops, and shopping malls. When the coronavirus epidemic began around the world, the strategy of herd immunity was discussed in many countries. Although in the end no country has walked that path but the path of lockdown.
This is because before the invention of the vaccine, the number of people who would naturally be infected to develop herd immunity, and the number of people who would die, would be huge.
What is herd immunity?
When a high percentage of the population is vaccinated, it is difficult for infectious diseases to spread, because there are not many people who can be infected. For example, if someone with measles is surrounded by people who are vaccinated against measles, the disease cannot easily be passed on to anyone, and it will quickly disappear again. This is called ‘herd immunity’, ‘community immunity’ or ‘herd protection’, and it gives protection to vulnerable people such as newborn babies, elderly people and those who are too sick to be vaccinated.
Herd immunity does not protect against all vaccine-preventable diseases. The best example of this is tetanus, which is caught from bacteria in the environment, not from other people who have the disease. No matter how many people around you are vaccinated against tetanus, it will not protect you from tetanus.
How does herd immunity work?
Herd immunity only works if most people in the population are vaccinated (for example, 19 out of every 20 people need to be vaccinated against measles to protect people who are not vaccinated). If people are not vaccinated, herd immunity is not guaranteed to protect them. Vaccination rates are high in the UK as a whole, but this hides the fact that rates are much lower in some parts of the UK and in some communities.
If you live in an area where vaccine coverage is low, and your child is not vaccinated, it’s quite likely that many of the people they come into contact with will not be vaccinated either. If one of these people gets an infectious disease like measles, they can easily pass it on to the other unvaccinated people around them, and in some cases the disease can then spread very quickly through the population. This is what happened during the 2013 measles outbreak in Wales.
Unlike vaccination, herd immunity does not give a high level of individual protection, and so it is not a good alternative to getting vaccinated.
Could herd immunity be an option for Bangladesh?
Commenting on the issue Dr Taufique Joarder, a public health expert, said, “Most of the scientists are against the idea of herd immunity in terms of fighting coronavirus because the concept is generally used in relation to developing vaccines where there is no risk of death. But when immunity is sought to be acquired in a natural process, instead of vaccines – which means to allow people to get infected and build a sort of defense from further infections – the control is not in our hands, rather the virus itself has the control.”
“We know that different diseases have different case fatalities. These case fatalities in terms of Covid-19 are two to three percent. So, adopting herd immunity as our strategy to address Covid-19 means to allow a very large section of people to get infected and eventually die,” he added.
In such a case, Dr Taufique Joarder, an Executive Director of Public Health Foundation Bangladesh, said that two things need to be considered; firstly, when tens of thousands of people will get infected, our healthcare system will collapse, the number of deaths will be enormous and a tremendous humanitarian disaster could ensue.
Secondly, enough research has not been conducted about the effectiveness of herd immunity in addressing Covid-19. We are not certain if this would rule out the possibilities of reinfection.
For the sake of argument, suppose we adopt herd immunity and allow a subsequent disaster in our healthcare system, damage our economy and let tens of thousands of people get infected and die only to find that people are getting re-infected. In such a scenario, we just lose everything.
“So, herd immunity cannot be an option for Bangladesh…. It just cannot be,” commented Dr Taufique Joarder, who teaches Johns Hopkins Bloomberg School of Public Health in the USA.
As no antidote or vaccine for coronavirus has yet been discovered. So how will herd immunity work to deal with it?
In this case, it is said that those who are once infected with the virus, the immune system against the virus is strong. In this way, if more people become infected with the virus, then at one time a large number of people develop immunity to the virus. This creates a protective zone within a particular community and stops the spread of the disease.
Former Director of the Department of Disease Control of DGHS Benazir Ahmed said it is difficult to work herd immunity in the case of coronavirus. Because, more than 90 per cent of people need to be infected with the virus if they are to develop strong immunity (herd immunity) against the coronavirus.
“It is not yet a recognized method of coronavirus prevention. But many think it could be a way,” he added.
According to the World Health Organization, a person infected with coronavirus can infect 2.5 people.
If there is to be hard immunity in the case of Bangladesh, about 160 million people out of 170 million will have to be infected with coronavirus. So, 160 million to be infected and 0.001 per cent of them have to be hospitalized. If we think about the current health system in Bangladesh, it is impossible to provide the facility to such huge number of patients, according to scientific analysis.
“I am totally against the herd immunity theory as the country does not have the infrastructure to provide treatment to a large number of infected people,” Dr. Ahmed said.
He said the corona cases in the country have already crossed over 10,000 amid inadequate preventive measures. This would not be happened if the quarantine measures enforced properly with halt in international flights. This situation may not arise if the overseas passengers have stopped to enter the country.
Ahmed said that the decision of the reopening the garment factories s and relaxing of the lockdown was tantamount to “neglecting the preventive measures”.
“For this, we have to pay the price,” he said.
