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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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Difference Between Sadness and Depression: Understanding Normal Emotions vs Mental Illness

Feeling low or unhappy is a part of being human. However, not all low moods are the same. Many people confuse sadness with depression, which can delay proper support and treatment. Understanding the difference between sadness and depression is crucial for mental health awareness, early intervention and reducing stigma.

In India, mental health conditions are often misunderstood, with emotional distress frequently dismissed as temporary sadness.

What Is Sadness?

Sadness is a normal human emotion.

It usually occurs due to:

loss or disappointment
relationship issues
failure or stress
temporary life challenges

Sadness serves a psychological purpose, allowing individuals to process emotions and adapt.

Key Characteristics of Sadness

Sadness is:

situational
temporary
emotionally painful but manageable
responsive to support and positive events

A person experiencing sadness can still function, enjoy moments and feel hopeful.

What Is Depression?

Depression is a medical condition classified as a mood disorder.

It affects:

emotions
thinking patterns
behaviour
physical health

According to WHO, depression is one of the leading causes of disability worldwide.

Core Symptoms of Depression

Depression involves a combination of symptoms such as:

persistent low mood
loss of interest or pleasure
fatigue
sleep disturbances
appetite changes
feelings of worthlessness
difficulty concentrating

These symptoms last at least two weeks or longer.

Duration: A Key Difference

One major difference lies in duration.

Sadness:

lasts hours or days
improves with time

Depression:

lasts weeks or months
persists despite positive events

Duration helps distinguish emotional response from illness.

Impact on Daily Functioning

Sadness:

allows continuation of work and relationships
may reduce motivation temporarily

Depression:

interferes with work, studies and relationships
reduces self-care and productivity

Functional impairment is a defining feature of depression.

Emotional Experience: Sadness vs Depression

Sadness:

allows emotional range
moments of joy still occur

Depression:

creates emotional numbness
joy and interest disappear

People with depression often describe feeling empty rather than sad.

Physical Symptoms in Depression

Depression is not only emotional.

Physical symptoms include:

chronic fatigue
body aches
headaches
digestive issues

ICMR mental health studies highlight the physical burden of depression.

Thought Patterns and Self-Perception

Sadness:

thoughts remain realistic
self-worth is preserved

Depression:

negative self-talk dominates
feelings of guilt and worthlessness increase

These cognitive changes deepen emotional suffering.

Risk Factors for Depression

Factors increasing depression risk include:

chronic stress
trauma
family history
medical illnesses
hormonal changes

NFHS-5 data indicates rising mental health concerns among young adults.

Can Sadness Turn Into Depression?

Yes, prolonged or unresolved sadness can progress into depression.

This is more likely when:

stressors are ongoing
support systems are weak
coping mechanisms are limited

Early emotional support can prevent progression.

When to Seek Professional Help

Seek help if:

low mood lasts more than two weeks
daily functioning is affected
sleep and appetite are disturbed
thoughts of self-harm occur

Early care leads to better outcomes.

Treatment Differences

Sadness:

improves with rest, support and time

Depression:

requires psychotherapy
may need medication
benefits from structured care

WHO emphasises early treatment to reduce disability.

Role of Social Support

Support systems help both conditions but are essential for recovery.

Depression recovery improves with:

understanding family
supportive workplaces
accessible mental healthcare

Stigma reduction is key.

Mental Health Awareness in India

Mental health remains underdiagnosed in India.

NITI Aayog reports:

limited access to mental health services
low awareness
high stigma

Education helps bridge this gap.

Importance of Early Recognition

Recognising depression early:

prevents worsening
reduces suicide risk
improves quality of life

Delay increases suffering and complications.

Supporting Someone With Depression

Helpful actions include:

listening without judgement
encouraging professional help
avoiding minimising feelings

Compassion is more effective than advice.

Conclusion

Understanding the difference between sadness and depression is essential for emotional wellbeing and mental health care. Sadness is a natural, temporary response to life events, while depression is a serious medical condition that affects thoughts, emotions and daily functioning. Recognising the signs early and seeking appropriate help can prevent long-term suffering and promote recovery. Mental health deserves the same attention and care as physical health.

References

World Health Organization (WHO) – Depression and Mental Health Disorders
Indian Council of Medical Research (ICMR) – Mental Health Research and Burden
National Family Health Survey (NFHS-5) – Mental Health Indicators
Lancet – Depression, Disability and Public Health
NITI Aayog – National Mental Health Policy and Awareness Reports
Statista – Global and Indian Mental Health Trends

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