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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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Asthma Symptoms in Adults: Early Signs, Triggers, and When to Seek Care

Asthma is often perceived as a childhood condition, but a significant number of cases develop or persist into adulthood. In India, adult asthma is increasingly recognised due to rising air pollution, occupational exposure and lifestyle-related risk factors. Unfortunately, asthma symptoms in adults are frequently misdiagnosed as recurrent infections, allergies or age-related breathlessness, leading to delayed treatment.

Understanding adult asthma symptoms is critical for early diagnosis, effective control and prevention of severe attacks.

What Is Asthma?

Asthma is a chronic inflammatory disease of the airways. In asthma, the airways become:

inflamed
narrow
overly sensitive to triggers

This leads to difficulty in breathing, especially during exposure to specific stimuli.

Why Adult Asthma Is Often Missed

Adult asthma symptoms may:

appear gradually
vary in severity
mimic common respiratory conditions

According to Indian Council of Medical Research and WHO data, many adults remain undiagnosed for years, increasing the risk of complications.

Common Asthma Symptoms in Adults

Wheezing

A high-pitched whistling sound while breathing, especially during exhalation, is a classic asthma sign.

Shortness of Breath

Adults with asthma often feel:

breathless during routine activities
difficulty taking deep breaths

This may worsen at night or early morning.

Chest Tightness

Many describe a sensation of pressure or tightness in the chest, which can be mistaken for heart-related issues.

Chronic Cough

A persistent cough, especially:

at night
early morning
after exercise

is a common but overlooked asthma symptom.

Symptoms That Worsen With Triggers

Asthma symptoms often intensify after exposure to specific triggers.

Air Pollution and Smoke

Urban pollution, vehicle emissions and indoor smoke significantly worsen asthma symptoms in adults.

Allergens

Dust mites, pollen, mould and pet dander are common triggers.

Respiratory Infections

Viral infections can trigger asthma flare-ups or reveal undiagnosed asthma.

Physical Activity

Exercise-induced asthma causes breathlessness and wheezing during or after physical exertion.

Weather Changes

Cold air, humidity and sudden temperature changes can aggravate symptoms.

Adult-Onset Asthma

Adult-onset asthma differs from childhood asthma.

Characteristics include:

onset after age 20–30
less association with childhood allergies
more persistent symptoms
higher likelihood of severe disease

Occupational exposure and hormonal changes contribute to adult-onset asthma.

Risk Factors for Asthma in Adults

Several factors increase asthma risk:

long-term exposure to pollution
smoking or passive smoking
occupational chemicals or dust
obesity
family history of asthma
chronic sinusitis or allergies

Women may experience asthma onset or worsening during hormonal changes.

When Asthma Symptoms Become Serious

Seek immediate medical attention if experiencing:

severe breathlessness
difficulty speaking in full sentences
bluish lips or fingertips
rapid worsening of symptoms
poor response to usual inhalers

These signs indicate a potentially life-threatening asthma attack.

How Adult Asthma Is Diagnosed

Diagnosis includes:

detailed symptom history
physical examination
lung function tests (spirometry)
response to bronchodilators

Early diagnosis improves long-term outcomes.

Impact of Untreated Asthma

Untreated asthma can lead to:

frequent attacks
reduced lung function
sleep disturbances
missed workdays
reduced quality of life

According to Lancet respiratory studies, uncontrolled asthma increases hospitalisation risk.

Managing Asthma Symptoms in Adults

Effective asthma management focuses on:

identifying and avoiding triggers
using prescribed inhalers correctly
monitoring symptoms regularly
maintaining follow-up care

Asthma action plans help patients recognise worsening symptoms early.

Role of Preventive Healthcare

Preventive healthcare helps:

detect asthma early
assess lung function
guide lifestyle modifications

Regular health checkups are especially important for individuals with respiratory symptoms or occupational exposure.

Lifestyle Measures That Support Asthma Control

Helpful practices include:

avoiding smoking
improving indoor air quality
wearing masks in polluted environments
maintaining healthy weight
regular, moderate exercise

Lifestyle support complements medical treatment.

Mental Health and Asthma

Stress and anxiety can worsen asthma symptoms.

Stress management:

reduces symptom frequency
improves medication response

Holistic care improves asthma outcomes.

Importance of Medication Adherence

Asthma medications work best when:

taken regularly as prescribed
inhaler technique is correct

Skipping treatment increases flare-up risk.

Long-Term Outlook for Adults With Asthma

With proper management:

symptoms are well controlled
severe attacks are preventable
normal activity levels are achievable

Most adults with asthma lead active, productive lives.

Conclusion

Asthma symptoms in adults are often subtle, variable and easily mistaken for common respiratory problems. Wheezing, breathlessness, chest tightness and chronic cough should not be ignored, especially when triggered by pollution, exercise or weather changes. Early diagnosis, trigger control and consistent treatment are essential to prevent severe attacks and preserve lung health. Recognising adult asthma early empowers individuals to manage symptoms effectively and maintain a good quality of life.

References

Indian Council of Medical Research (ICMR) – Respiratory Disease and Asthma Studies
World Health Organization (WHO) – Asthma Management and Prevention Guidelines
National Family Health Survey (NFHS-5) – Respiratory Health Indicators
Lancet Respiratory Medicine – Adult Asthma Outcomes and Management
NITI Aayog – Air Pollution and Respiratory Health Reports
Statista – Global Asthma Prevalence and Trends

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