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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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Shortness of Breath Causes: From Common Triggers to Serious Health Conditions

Shortness of breath, medically known as dyspnea, is a symptom that ranges from mild discomfort during exertion to a distressing sensation of not getting enough air. In India, increasing air pollution, lifestyle diseases and respiratory infections have made breathlessness a frequent complaint across age groups. Understanding shortness of breath causes is essential to identify when it is harmless and when it signals a medical emergency.

What Is Shortness of Breath?

Shortness of breath refers to difficulty breathing or a feeling of air hunger.

It may present as:

rapid breathing
shallow breathing
tightness in the chest
inability to take a deep breath

The sensation can develop suddenly or gradually.

Common and Benign Causes of Shortness of Breath

Physical Exertion

During exercise, the body demands more oxygen.

Temporary breathlessness during:

climbing stairs
running
heavy physical work

is normal and resolves with rest.

Anxiety and Panic Attacks

Stress and anxiety alter breathing patterns.

Symptoms include:

rapid breathing
chest tightness
dizziness

These episodes often resolve with calming techniques.

Respiratory Causes of Shortness of Breath

Asthma

Asthma causes airway narrowing and inflammation.

Symptoms include:

wheezing
chest tightness
breathlessness during exertion or at night

Asthma is a leading cause of chronic breathlessness.

Chronic Obstructive Pulmonary Disease

COPD includes chronic bronchitis and emphysema.

Risk factors include:

smoking
indoor air pollution
occupational exposure

WHO identifies COPD as a major cause of breathlessness in adults.

Respiratory Infections

Infections such as pneumonia and bronchitis reduce lung capacity.

Breathlessness may be accompanied by:

cough
fever
chest pain

Severe infections require urgent treatment.

Heart-Related Causes of Shortness of Breath

Heart Failure

The heart fails to pump blood efficiently.

This leads to:

fluid accumulation in lungs
breathlessness on exertion
breathlessness while lying flat

ICMR data shows heart disease as a major contributor to unexplained breathlessness.

Coronary Artery Disease

Reduced blood supply to the heart can cause:

breathlessness
chest discomfort
fatigue

This may occur even without chest pain in some individuals.

Blood and Metabolic Causes

Anemia

Low hemoglobin reduces oxygen delivery.

Common symptoms include:

fatigue
breathlessness on mild activity
pale skin

NFHS-5 highlights anemia as highly prevalent in India.

Thyroid Disorders

Hyperthyroidism increases metabolic demand, causing breathlessness.

Hypothyroidism may contribute indirectly through weight gain and reduced stamina.

Lung Circulation Disorders

Pulmonary Embolism

A blood clot in the lungs causes sudden, severe breathlessness.

This is a medical emergency and may be accompanied by:

chest pain
coughing blood
fainting

Immediate treatment is critical.

Lifestyle-Related Causes

Obesity

Excess body weight restricts lung expansion.

Breathlessness occurs due to:

increased oxygen demand
reduced lung volumes

Weight management improves breathing efficiency.

Sedentary Lifestyle

Poor physical conditioning reduces respiratory muscle strength.

Even mild exertion may cause breathlessness.

Environmental and Occupational Factors

Air Pollution

Pollutants irritate airways and reduce lung function.

Urban populations experience higher rates of breathlessness.

Workplace Exposure

Dust, chemicals and fumes increase respiratory risk.

Protective measures are essential in high-risk occupations.

When Shortness of Breath Is a Warning Sign

Seek urgent care if breathlessness:

starts suddenly
worsens rapidly
occurs at rest
is associated with chest pain, bluish lips or confusion

These may indicate life-threatening conditions.

How Shortness of Breath Is Diagnosed

Evaluation may include:

physical examination
chest imaging
blood tests
lung function tests
heart evaluation

Diagnosis focuses on identifying the root cause.

Preventive Measures and Lifestyle Care

Prevention includes:

regular physical activity
pollution protection
smoking cessation
weight control
managing chronic conditions

Preventive healthcare reduces long-term risk.

Importance of Early Medical Evaluation

Delayed diagnosis can worsen outcomes, especially in:

heart disease
lung infections
anemia

Early care improves treatment success.

Conclusion

Shortness of breath causes range from temporary exertion and anxiety to serious heart, lung and blood disorders. While occasional breathlessness may be harmless, persistent or sudden symptoms should never be ignored. Understanding the underlying causes and seeking timely medical evaluation can prevent complications and save lives. Paying attention to changes in breathing is an essential step toward protecting overall health and wellbeing.

References

Indian Council of Medical Research (ICMR) – Respiratory and Cardiac Health Reports
World Health Organization (WHO) – Breathlessness and Chronic Disease Guidelines
National Family Health Survey (NFHS-5) – Anemia and Respiratory Health Data
Lancet – Dyspnea Evaluation and Outcomes Research
NITI Aayog – Non-Communicable Disease Prevention Reports
Statista – Respiratory Disease and Air Pollution Trends

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