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Published on: Apr 20, 2020
3 minute read
By: Dr Rajan Choudhary

Is Herd Immunity A Valid Strategy For COVID 19?

Yesterday we explained you what Herd Immunity means and how it works, today we will take the discussion further to determine whether it is effective and can be recommended in the current context.

COVID-19 currently does not have a cure or a vaccine. Lockdown is the only strategy that appears to be working. Could implementing policies that encourages herd immunity be used to accelerate immunity in the population without the need for a vaccine?

INFECTIVITY

For the strategy to work we need to know a few things about the virus. How infective is it? In one of our earliest blogs we discussed infectivity at length and determined that the R0 (infectivity) may be between 2 and 3. This means each person with the virus can infect around 2-3 people at a time. Whilst this is not as high as Mumps (10-12) it is much higher than the common flu. The higher the R0 the more people that need to be immunised before herd immunity is achieved. For COVID it is estimated that 70% of the population need to be infected.

This is based off our current testing. Due to shortages in testing kits, only testing those that have a high likelihood of being infected and poorly organised testing infrastructure in some countries, we are likely underestimating. The number of people infected may be much higher as we are missing those that are asymptomatic but still have the disease and are still passing the disease on.

MORTALITY

Secondly, we need to know the mortality from COVID-19. Early estimates of mortality were as high as 10%, as we had little data on how many people were truly infected, but as the number of infected cases rose, and testing amongst the infected and symptomatic population rose, a more accurate mortality has been found to be around 1%. There is a risk we may still be underestimating the true mortality, as some cities have noted a spike in cardiac deaths, and some evidence supports possible cardiac damage due to COVID. But from the data we have, we know its mortality is lower than MERS (34%) and SARS (10%) but more than influenza (0.1%).

estimates of the COVID-19 case fatality rate

Whilst we have some data on who is likely to suffer from severe COVID symptoms (elderly, immunocompromised, people with heart or lung problems) we still cannot accurately determine who will get severe COVID in the “low risk” population. Simply because someone is young and healthy does not mean they will not die from COVID.

LENGTH OF IMMUNITY

Third we need to know how long this immunity will last. Similar coronaviruses responsible for the common cold usually create immunity that lasts for a few months, which is why we often get the cold repeatedly. A virus is also very prone to mutations that can change the structure and functions of its proteins, proteins responsible for tagging, latching on to and entering cells. If the structure of these proteins changes enough, then our antibodies will not be able to bind on, and new types of antibodies will have to be made with a slightly different structure. This effectively means our bodies have to start from step 1 again to create immunity, and we have to make new vaccines. This mutation rate is why we have to make new vaccines every season for the flu.

LONG TERM COMPLICATIONS

Finally, we need to know if there are any long-term implications from a viral infection. Again, this is something we do not know yet, as the virus has only been around for a few months. There may be implications for the cardiovascular system, long term breathing problems or more. And even if the complication rate appears relatively low (say, 1%), if millions of people are allowed to get infected, by definitions thousands or tens of thousands of people will have these complications, complications that can lead to issues later in life or an early death.

CONCLUSION

So, is herd immunity a viable strategy for COVID? Without a safe vaccine the general consensus appears to be no.

We don’t know how infective the virus really is or how many people it has infected

A 1% death rate is still very high. This means for every 100 people to be infected; one will die. This would mean hundreds of thousands of people dead in a country with a population over 10 million. It is unacceptably high.

If the death rate is 1%, then hospitalisation rate is likely higher. Almost all countries do not have capacity to have 1% of the population in hospital. Overwhelming the healthcare system will lead to poorer care, and worse care for those who do not have COVID. Leading to more people coming to serious harm or dying as a result of poor healthcare, not because of COVID.

We don’t know the long-term effects of COVID. By purposefully infecting people instead of waiting for a vaccine we may be causing unnecessary damage to a person’s health that only becomes apparent later in life. But this is speculation as we do not currently know if COVID has long term effects,

We don’t know if all of the risks above will amount to anything. The immunity may not last long enough, leading to another spike in infections and mortality.

Mass vaccination appears to be the safest strategy. And though human clinical trials have started on a number of vaccines, we are still months away from deployment. Until then we should not come out of lockdown prematurely, not until we have received an unbiased assessment from public health officials that states it is safe.

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Air Pollution & Respiratory Health: Understanding the Impact and Taking Action

Introduction

Air pollution has become a growing concern in India, especially in urban and industrial areas. One of the most serious effects of air pollution is its impact on respiratory health. As pollution levels continue to rise, it’s important for people to understand how polluted air affects their lungs and overall breathing. This blog will explain what air pollution is, how it harms the respiratory system, and what steps you can take to protect yourself and your loved ones.

What is Air Pollution?

Air pollution is the presence of harmful substances in the air that we breathe. These substances, known as pollutants, can come from both natural and man-made sources. The major air pollutants include:

Particulate Matter (PM2.5 and PM10) – Tiny particles from vehicles, factories, and construction that can enter the lungs.
Carbon Monoxide (CO) – A colorless gas produced by burning fuel.
Nitrogen Dioxide (NO?) – Released from vehicle exhaust and industrial activities.
Sulfur Dioxide (SO?) – Mainly from burning coal and oil.
Ozone (O?) – A gas that forms when sunlight reacts with pollutants.

These pollutants are invisible but have a big impact on our health, especially when inhaled over long periods.

Sources of Air Pollution in India

In India, air pollution comes from a variety of sources:

Vehicle emissions – The rising number of cars and bikes contribute heavily to pollution, especially in cities.
Industrial discharge – Factories and power plants release gases and smoke into the air.
Construction dust – Rapid urban development leads to dust and debris in the air.
Burning of biomass – In rural areas, wood, dung, and crop residues are often burned for cooking or heating.
Stubble burning – Common in northern states during harvest seasons.
Household emissions – Use of traditional stoves and fuels in homes adds to indoor pollution.

Together, these factors make the air in many Indian cities dangerous to breathe.

How Air Pollution Affects Respiratory Health

The respiratory system includes the nose, throat, windpipe, and lungs. When we breathe in polluted air, harmful particles and gases enter the body and cause a number of problems:

1. Asthma

Pollution can trigger asthma attacks or make existing asthma worse. It causes inflammation in the airways, making it hard to breathe.

2. Chronic Obstructive Pulmonary Disease (COPD)

This includes long-term conditions like chronic bronchitis and emphysema. Exposure to polluted air over time is a major risk factor for COPD.

3. Lung Cancer

Long-term exposure to fine particulate matter (PM2.5) increases the risk of developing lung cancer, even in people who don’t smoke.

4. Respiratory Infections

Children and elderly people are especially prone to infections like pneumonia and bronchitis when the air is polluted.

5. Worsening of Existing Conditions

For people already suffering from respiratory diseases, poor air quality can lead to more frequent doctor visits and hospitalizations.

Who is Most at Risk?

While air pollution affects everyone, some people are more vulnerable:

Children – Their lungs are still developing, and they breathe faster, which means they inhale more pollutants.
Elderly people – They often have weaker immune systems and pre-existing health problems.
People with lung or heart conditions – They may suffer more severely from pollution.
Outdoor workers – People like traffic police, street vendors, and construction workers are at greater risk due to long hours spent outside.

Air Pollution in Indian Cities

Several Indian cities are among the most polluted in the world. Cities like Delhi, Kanpur, Patna, and Lucknow often report extremely high levels of PM2.5, especially in winter. During these times, the air quality can be so poor that it is considered "hazardous." This not only affects day-to-day health but also reduces life expectancy over the long term.

Steps You Can Take to Protect Yourself

While it may not be possible to eliminate air pollution immediately, there are many things individuals can do to reduce their risk:

1. Check Air Quality Index (AQI)

Use AQI apps or websites to stay informed. Avoid outdoor activities when air quality is very poor.

2. Use Masks

Wearing an N95 or N99 mask helps filter out harmful particles when pollution is high.

3. Stay Indoors

On days with high pollution levels, try to stay indoors, especially during peak traffic hours.

4. Use Air Purifiers

Installing air purifiers at home can help improve indoor air quality, particularly for those with respiratory problems.

5. Improve Ventilation

Ensure good airflow in your home but avoid opening windows during high-pollution periods.

6. Plant Trees

Green spaces help clean the air. If possible, plant trees or keep air-purifying indoor plants like snake plant, aloe vera, or peace lily.

7. Switch to Cleaner Fuels

Using LPG or electricity for cooking instead of wood or coal helps reduce indoor air pollution.

What Can Communities and Governments Do?

Large-scale solutions require action from the government and communities:

Promoting public transport and reducing the number of private vehicles.
Controlling industrial emissions and enforcing pollution control norms.
Creating green zones and increasing tree cover in cities.
Encouraging use of cleaner fuels and technologies in homes and factories.
Educating people about the risks of pollution and how to protect themselves.

Conclusion

Air pollution is a serious threat to respiratory health, especially in a country like India where pollution levels are high in many areas. From asthma to lung cancer, the effects can be severe and long-lasting. However, by staying informed and taking simple precautions, individuals can reduce their risk. It’s also important to support broader actions that aim to reduce pollution at the source.

If you’re concerned about how pollution may be affecting your breathing or health, talk to a healthcare expert. Protect your lungs, stay informed, and take action—because Air Pollution & Respiratory Health should never be ignored.