• Published on: Apr 19, 2020
  • 3 minute read
  • By: Dr Rajan Choudhary

What Is Herd Immunity With Respect To Covid19 ?

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Herd immunity: the basics

Many countries have been in lockdown for over a month, and some have tried to begin the discussion of an exit strategy. We know that remaining in lockdown continuously is not a feasible strategy, as many people have been suffering economic consequences from the stringent lockdown measures, and many countries have been providing significant monetary and fiscal support for people and businesses at risk. But leaving lockdown too early has its own consequences.

Almost all public health professionals will agree that the lockdown has been able to significantly reduce infection rates and reduce the pressure on our healthcare systems. By taking this early victory and prematurely ending lockdown we risk another wave of infections, reintroducing lockdown, and having an overall negative effect on the general health of the populous.

So what can we do? One exit strategy that has been touted recently is herd immunity. To understand how to may work for COVID we must understand what epidemiologists mean by herd immunity.

IMMUNITY

Our body’s immune system fights against invading organisms such as bacteria and viruses. For a more in-depth discussion you can have a look at previous blogs on Vaccines and Boosting the Immune system. The immune system is very competent and has mechanisms to theoretically recognise any protein tags that do not belong to that person’s cells, even protein tags that do not currently exist in nature. This gives the immune system the ability to theoretically recognise nearly any invading organism that has existed or will ever exist.

The immune system goes beyond this as well and produces “memory cells”. These remain in the blood after an infection for a long time; in some cases, it can even be lifelong. When a second infection occurs from the same organism the immune system jumps into action and is able to produce antibodies against the invader almost immediately. This can neutralise the invader before it has a chance to replicate, cause severe symptoms and harm the body. Sometimes we never realise we have been infected as the infection never gets a chance to cause any damage.

Importantly, if the invader cannot replicate in our body, then its ability to spread to other people is also reduced. For example, respiratory viruses can rapidly replicate in our lungs and be transmitted when we cough or sneeze. By eliminating the virus before it can replicate extensively the number of viral particles in each cough and sneeze is reduced, reducing the chances of another person catching the infection.

This is the basis of how vaccines work and is covered in depth in the two part blog.

HERD IMMUNITY

If our immune system is so competent, why do we need to worry about infections at all? Surely we can all get infected and gain immunity. In an ideal world where everyone was healthy this may be true. But there are many people who do not have fully functioning immune systems. These people are immunocompromised and can be for many reasons.

  • Chemotherapy and radiotherapy for cancer destroys rapidly dividing cells such as cancer cells. Unfortunately, it also hits other dividing cells, such as hair follicles, gut lining and the bone marrow, which produce the white blood cells that give us immunity. Chemotherapy patients are very susceptible to even the mildest of infections. Even if a mild infection is suspected, they are treated aggressively with antibiotics, as their lowered immune systems can become overwhelmed very quickly.
  • Sometimes doctors advise patients to take medication that purposefully dampens the immune system. This is necessary for transplant patients, where the host immune system attacks the donor organ as it does not belong to the host, or in autoimmune disorders, where the immune system attacks the host by mistakenly recognising it as an “invader”.
  • Taking steroids long term has a similar effect, and is used quite commonly for skin disorders, asthma, COPD, and other inflammatory conditions.
  • People with various chronic illnesses can have reduced immunity as a result of the illness. High sugar levels associated with poorly controlled diabetes can cause worsening organ function, including the immune system. These patients are more susceptible to infections.
  • Finally, some people do not have fully functioning or welldeveloped immune systems for a variety of reasons, inherited or acquired. As we get older, the immune system function decreases, and simple infections can be devastating.

In all of these cases the ability to recognise invading organisms, destroy them and form immunity is hampered. Vaccination, one way of inducing immunity without causing the person to suffer from a full-blown infection, can also be ineffective in these patients, and some vaccines can be dangerous if used incorrectly. So how do we protect these vulnerable patients?

HERD IMMUNITY

This is where we go back to the earlier point. Immunity in healthy people can reduce or even prevent the spread of infection from one person to another. The number of healthy people outnumber the number of vulnerable, immunocompromised ones. Therefore, if we induce immunity in most people, the infection will simply not spread to the vulnerable ones. We don’t have to immunise everyone, just enough to prevent transmission. This is called herd immunity. This is why we immunise everyone with flu vaccines even those that are healthy and will survive a full blown infection. Because by preventing these people from inadvertently spreading the flu, they will protect those that we cannot immunise.

Does herd immunity work? For most other diseases, yes. It depends on how the disease is spread, and how infective it is. For measles, you need to immunise 19 out of 20 people to achieve herd immunity, because it is so infective. But once herd immunity was achieved death rates were drastically reduced. With the advent of anti-vaccine campaigns, particularly against MMR, this herd immunity has been lost, and many vulnerable children (and adults) who do not have fully functioning immune systems are now contracting this virus and dying from a preventable disease.

It can be achieved for pandemics as well. Norway was able to achieve partial herd immunity to H1N1 (swine flu) through a vaccination program and natural immunity. Vaccines are the best method for achieving herd immunity without extremely high death rates. We have already covered the issues with making a vaccine, and why it takes such a long time, in our previous blog

From reading this blog you should now have an understanding of what herd immunity is, and why it is important in protecting those that are vulnerable to infections. In our next blog we will look at why herd immunity may not be the solution for COVID-19.

Dr Rajan Choudhary, UK, Chief Product Officer, Second Medic Inc

www.secondmedic.com

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Nutritional Deficiencies in Indian Kids

Nutritional Deficiencies in Indian Kids: Recognizing, Preventing & Overcoming “Hidden Hunger”

Every parent wants their child to grow up healthy — tall, strong, smart, and full of energy. But in India, many kids suffer from what is known as “hidden hunger.” It means that even though they are eating, their diet lacks essential nutrients. These nutritional deficiencies can affect growth, learning, immunity, and long-term health. In this blog, we’ll explore the major nutritional deficiencies in Indian kids, what causes them, how to detect them, and what parents can do. Let’s dive into nutritional deficiencies in Indian kids.

 

What Are the Most Common Nutritional Deficiencies?

Based on recent research and national surveys, the following are among the most widespread deficiencies in Indian children:

  • Iron Deficiency / Anaemia
    A large percentage of Indian kids (especially under-5s) have low hemoglobin and low iron stores. Anaemia can cause tiredness, slow cognitive development, and lowered immunity. Lippincott Journals+2PMC+2
     

  • Vitamin A Deficiency
    Vitamin A is essential for good vision, immunity, and healthy cells. Many children under 5 show sub-clinical deficiency; some show clinical signs like night blindness. Lippincott Journals+1
     

  • Iodine Deficiency
    Iodine is critical for thyroid hormone production, which affects brain development. Lack of iodine can lead to goitre, delayed mental development, and poor school performance. Lippincott Journals+2thyrocare.com+2
     

  • Vitamin D Deficiency
    Even though India is sunny, many children have low vitamin D — due to indoor living, limited sun exposure, skin coverage, or dietary gaps. This impacts bone health, growth, and risks rickets. PMC+1
     

  • Protein-Energy Malnutrition (PEM)
    In poorer or marginalized communities, children may not get enough protein or calories. This leads to underweight, wasting, stunting, and weakened immunity. Lippincott Journals+2HDFC ERGO+2
     

  • Other Micronutrients (Vitamin B12, folate, zinc etc.)
    Deficiencies in B12 & folate can affect cell division, blood production, nerve function; zinc deficiency weakens immunity & slows growth. PMC+2nanhedil.com+2
     

 

Why Do These Deficiencies Happen?

Understanding the causes helps in prevention:

  1. Dietary Factors
    Many diets are heavy in cereals or starches but low in diversity. Meals may lack fruits, vegetables, animal-source foods (meat, eggs, fish) or fortified products.
     

  2. Bioavailability of Nutrients
    Even when foods contain nutrients, they may not be absorbed well. For example, plant-based iron is less readily absorbed, phytates in grains and legumes can reduce absorption.
     

  3. Socioeconomic Constraints
    Poverty, food insecurity, access issues, lack of awareness, and sometimes traditional/cultural food beliefs limit access to nutrient-rich foods.
     

  4. Living Conditions and Health
    Frequent infections, parasitic infestations, poor hygiene, etc., can increase nutrient loss or demand. Also sunlight exposure (important for vitamin D) is inadequate in many cases.
     

  5. Gaps in Implementation of Prevention Programs
    Though India has multiple programs (fortification, supplement distribution, ICDS, National Nutrition Mission etc.), challenges remain in reach, compliance, quality, and behavioural change.
     

 

Effects of Nutritional Deficiencies

These deficiencies have short-term and long-term effects:

  • Growth stunting (children don’t reach their full height potential)
     

  • Wasting (low weight for height), underweight
     

  • Impaired cognitive development & learning difficulties
     

  • Weak immune system ? more infections
     

  • Delayed motor skills, poor school performance
     

  • Bone deformities (rickets, weak bones)
     

  • Poor quality of life; in severe cases, increased mortality
     

 

How to Detect & Diagnose Early

Taking action early helps avoid permanent harm. Key strategies include:

  • Regular growth monitoring: Checking weight, height, BMI for age
     

  • Look for signs: Pale skin or lips, tiredness, delayed milestones, frequent illness, bone pain or deformities (knees bowing, wrist/ankle enlargement)
     

  • Lab tests:
     

    • Haemoglobin & complete blood count
       

    • Serum ferritin for iron stores
       

    • Serum levels for vitamin A (retinol)
       

    • 25-OH vitamin D test
       

    • Serum B12, folate
       

    • Urinary iodine excretion or salt iodine test
       

    • Protein / albumin levels
       

Using broad vitamin profiles (like those from Thyrocare) can help screen for multiple deficiencies in one go.

 

Foods, Diet & Prevention: What Parents / Caregivers Can Do

Here are practical steps parents can take:

  • Diversify diet: Include pulses, legumes, eggs, dairy, meat (if non-vegetarian), fish; plenty of green leafy vegetables & fruits.
     

  • Fortified foods: Use iodised salt; choose cereals / milk products fortified with vitamins & iron.
     

  • Sunlight exposure: Encourage outdoor activities; even short daily sun exposure (face, arms) helps vitamin D.
     

  • Supplementation when needed: Under doctor guidance, provide vitamin A doses, iron/folic acid, vitamin D etc., especially in high-risk children.
     

  • Hygiene & health care: Prevent worm infections, diarrhoea etc. which can drain nutrients. Ensure vaccinations.
     

  • Education & awareness: Teach families importance of nutrition, balanced meals, what local foods can provide what nutrients.
     

 

What Parents Should Ask Healthcare Providers

  • Ask whether your child needs screening for deficiencies (e.g., iron, vitamin A, D, B12).
     

  • If lab tests are suggested, check whether it’s comprehensive or narrow, cost, and follow-up.
     

  • Seek help for dietary planning, perhaps from nutritionists or public health bodies.
     

  • Learn about local government/NGO programs—free or subsidized supplementation or fortified food programs.
     

 

When to Seek Medical Help

If your child has:

  • Persistent anaemia symptoms (very pale, lethargic)
     

  • Growth issues (falling off growth charts)
     

  • Bone deformities or pain
     

  • Severe or recurrent infections
     

  • Unusual signs like night blindness, goitre
     

Then get a medical evaluation. Early intervention can make a big difference.

 

Conclusion & Call to Action

Nutritional deficiencies in Indian kids are common—but many are preventable or treatable. By recognizing risks, ensuring good diet, doing appropriate lab tests, and using supplements or fortified foods when needed, children can grow healthier, smarter, and stronger.

If you’re concerned that your child may have one or more of these deficiencies, talk to a trusted pediatrician or nutritionist, and consider getting a comprehensive vitamin & nutrition profile done (for example through Thyrocare or SecondMedic) to know exactly where improvements are needed. Don’t wait—every child deserves a strong foundation.

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