Saturday, April 13, 2024


Dhaka Tribune

A pandemic won’t let us out cheaply

Why herd immunity is ultimately the solution

Update : 12 May 2020, 08:50 PM

Go ahead, you can laugh it out. It is really hard to eradicate infectious diseases. Did we ever realize that it had taken decades of vaccination, all over our planet, to eradicate smallpox? Polio vaccines have also been available for decades, but polio is still endemic in some countries, including Pakistan and Afghanistan! 

No fewer than five influenza pandemics have shaken the world in the last 150 years and influenza is still with us, even though an influenza vaccine has also been available for decades.

So what makes anybody think that Covid-19 will go away anytime soon? 

What is necessary for a pandemic to die down? Perhaps the best answer is that herd immunity needs to be developed.

Do we really understand herd immunity? To make it simple: It is when a large percentage of the population has been exposed to the disease and has become immune to it. So, if somebody who is not immune gets the disease, the disease can’t go around much, because people who are contacts of the infected person are already immune. Usually, about 70% of the population needs to be immune before herd immunity becomes a meaningful protection against the spread of the disease.

Next question: How does herd immunity develop? Before vaccines became available, this would happen by the spread of the virus through the population. A large number of people would be infected, many would die, but most would survive and become immune to the illness.

Only after the vaccines have become available would herd immunity be developed through universal immunization, or at least through mass immunization programs -- if the entire population could not be immunized. In this context, it must be remembered that even in developed countries, about 5% of people, called anti-vaxxers, refuse to have their children vaccinated. 

These include all the countries of our sub-continent. And that is exactly why outbreaks of measles continue to be reported in North America and Europe.

Vaccination is a desirable method for the development of herd immunity. However, the bad news is: There is no Covid-19 vaccine presently available. We are going through trials of a new drug “remdesivir.”

If the Covid-19 pandemic has to end, it will end only when herd immunity develops, and that will happen either after (at least) 70% of the population has been exposed, because the virus has run through the population, or after universal immunization has been achieved with an effective vaccine against the disease.

During the present crisis, there are about 115 vaccines presently under development, of which at least six have reached the stage of testing in humans. It usually takes 5-10 years for vaccine development. Even if a Covid-19 vaccine is developed at the fastest possible pace, safety speed breakers will line the way. After all, it would not do for billions of humans to be vaccinated only to find that the vaccine has unintended consequences in a small percentage of persons. 

A small percentage of billions of humans translates into a very large number of humans.

The latest estimate is that it could take at least 18 months for a Covid-19 vaccine to reach us. That’s a long time to wait for vaccine-associated herd immunity. So we must learn to live with the idea that Covid-19 will be with us for a long time ahead.

We need to bear in mind that learning to live with Covid-19 must involve solutions that reduce Covid-19 deaths without disproportionately increasing morbidity and mortality from other causes. 

All lockdowns are good to the extent that these slow the spread of the virus and buy time until a treatment is discovered, or until a vaccine becomes available. Unfortunately, discovering a treatment or making a vaccine for a new disease is not something that is easily done; HIV/AIDS, SARS, MERS, and Ebola are viral diseases that are excellent examples of this. And as already mentioned earlier ... the vaccine is still far, far away!

And, lockdowns are also bad to the extent that they deny patients with other diseases the opportunity to obtain treatment for those diseases, and so people will suffer and/or die from it. Lockdown is particularly problematic where it harms the economy, thereby compromising the funds available for health care. 

Even before lockdown, a Global Burden of Diseases study found that, all over our sub-continent, nearly 6,000 children aged 0-5 years were known to be dying of malnutrition each day. In a lockdown-affected economy, the number of malnutrition deaths would be far higher.

These 6,000 or so deaths daily are only for malnutrition and only for children in a narrow age band. What about other communicable and non-communicable diseases, and persons in other age bands, most especially the elderly who already have a heavy burden of diseases accumulated during their lifetime?

If the lockdown is lifted, people will die as Covid-19 spreads. If the lockdown is extended, people will die of other causes. This is the harsh new reality. Should the health care industry add Covid-19 to the list of cardiovascular diseases, cancers, malnutrition, and other conditions that are currently leading causes of death?

Finally, there is some hope. Yes, a very slender hope. Covid-19 does not seem to be devastating the countries of India, Pakistan, Bangladesh as it has devastated Europe and North America. One hopes that this trend holds true as lockdown is lifted.

Let’s pray hard for safer days to return.

Nazarul Islam is an educator based in Chicago.



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