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Iqra Mazhar

Children and adults receive immunity through vaccination for various diseases. Vaccines help strengthen the immune system, besides innate immunity in the body.

The Chronicles Of Immunity

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Is Herd Immunity The Solution To Our Problems?

Introduction

When archaeologists dig up ancient cities buried under centuries of soil and history, they help uncover the evolution of human civilizations. From Mesopotamia to the Indus Valley, ancient civilizations have made several advances that continue to influence modern-day humans. These range from developments in culture, infrastructure, weapons, astronomy, engineering, printing, and much more. However, as humans built cities and waged wars, they also dealt with deadly pandemics that threatened to wipe out whole civilizations.&nbsp; 
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A pandemic is a name given to an infectious disease that has spread across borders and continents. On the other hand, diseases limited to a given population within an area is called an epidemic. Throughout history, several epidemics and pandemics have affected humans across the world.&nbsp; 
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The Black Death, or bubonic plague, is believed to be the most fatal pandemic in history. Occurring from 1346-1352, the disease is believed to have caused more than 25 million deaths in Europe<a href="#accordion">[1]</a>. However, this was not the first time that a plague caused widespread destruction. Earlier in 541 CE, the Plague of Justinian entered Constantinople and spread across Europe, North Africa, and Asia. It is estimated to have killed half of the world&#39;s population. At that moment in history, not much was known about fighting pandemics, so it is unclear what eventually <a href="https://merisehat.pk/page/sehat-a-z/">caused the disease</a> to die down. Researchers believe that majority of people who survived did so because of their immunity.&nbsp; 
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On the other hand, the spread of the Black Death was controlled through quarantine. The word quarantine was invented by the Venetians who imposed a 40-day isolation rule for all sailors entering the port city of Ragusa. 
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Till the 16th Century, isolating the sick became a part of disease control. It wasn&#39;t until Edward Jenner discovered the smallpox vaccine that vaccinations began to play a role in controlling infections. Prior to his invention, smallpox killed 3 out of every 10 people it infected<a href="#accordion">[2]</a>. Edward Jenner&#39;s experiment paved the way for future vaccines. And in 1980, the World Health Organization (WHO) announced the complete eradication of smallpox thanks to global vaccination programs. However, many researchers argue that herd immunity might have played a significant role in eradicating smallpox from the world. 
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But what is herd immunity? And where did it come from?

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While death and destruction were a common feature of World War I (WWI), several infectious diseases also wreaked havoc among civilians and soldiers. The chaotic wartime conditions characterized by malnourishment and poor hygiene conditions further spread infections among the masses. Moreover, the deadly influenza pandemic, also called Spanish flu, eclipsed the end of the first World War.&nbsp; 
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Thus, worried about the rising infections and looming threat of epidemics, in 1919, bacteriologists W.W.C. Topley and G.S. Wilson at the University of Manchester designed an experimental epidemic model with 15,000 mice<a href="#accordion">[3]</a>.&nbsp;The mice were allowed to move freely among the residential pods connected via tunnels. As part of the experiment, researchers exposed the laboratory mouse city models to deadly bacteria while another city received a vaccine and the bacteria. They noticed that despite not receiving vaccines, susceptible mice remained protected from bacterial infection. Thus, they proposed that immunity to an infection may be achieved if a certain proportion of the population became immune. They called this &quot;herd immunity.&quot;&nbsp; 
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Previously, veterinary scientists in the United States and Britain had used the term to describe the resistance to diseases among animals.&nbsp; 
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Later in the 1930s, researcher A. W. Hedrich used the term herd immunity to describe the decrease in the incidence of measles among children in Baltimore. He noticed that measles outbreaks seem to die down when a large number of children became immune due to a previous infection. Thus, the naturally occurring phenomenon also ended up protecting susceptible children.&nbsp;

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Understanding Herd Immunity And Its Impact On Public Health

Herd immunity results from a large proportion of the population becoming immune to an infectious disease. This reduces the risk of the spread of infection from person to person. As a result, people who are not immune are also protected. For example, if a sick person encounters four people, three of whom are immune to the disease, only one will go on to contract the infection. Moreover, the other three would not spread the disease further. Thus, instead of multiple cases leading to an outbreak, there will be a singular case which is easier to control and poses a lesser threat to public health.

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There are two ways to achieve herd immunity: natural infection and vaccines.&nbsp; 
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In case of a natural infection, the person forms antibodies that protect against future infections. However, these antibodies vary in amount depending on the person&#39;s immune system and provide them protection for a limited period only. Moreover, even if a large proportion of adults in a community develop immunity, the disease may still affect children. Therefore, herd immunity through natural infection is not the most reliable method. 
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Many researchers favor achieving herd immunity with the help of vaccines. They believe widespread vaccination of the population is the best way to achieve herd immunity and eliminate the disease from circulation. Through the introduction of a weakened or killed pathogen, vaccines induce an immune response in the body. Unlike a natural infection, vaccines can create immunity without the illness or risk of mortality and morbidity.&nbsp; 
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Over the years, several diseases have been controlled thanks to the vaccine herd effect. Vaccination against H. influenzae type b, pertussis, streptococcus pneumoniae, seasonal influenza, and rotavirus have all been shown to exert a herd effect<a href="#accordion">[4].</a> Maintenance of herd immunity in a population for an extended period can lead to the eventual elimination of the disease. So far, only two diseases have been eradicated using herd immunity and vaccination - smallpox and rinderpest in cattle. Researchers are currently working on eradicating poliomyelitis through herd immunity.&nbsp;

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Herd immunity helps protect vulnerable groups in the population and those that cannot receive vaccines. These include newborns, the elderly, cancer patients receiving chemotherapy, and other immunocompromised individuals. However, achieving herd immunity is no easy feat and nor does it always work. Following are the common barriers faced in reaching herd immunity: 
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<ul>
	<li>Vaccine Hesitancy - A refusal to get vaccinated leads to a lower proportion of vaccinated individuals in a community. As a result, the herd immunity threshold is not reached, and the infectious disease can continue to spread. Most people object to vaccines due to safety concerns, religious beliefs, and misinformation regarding the vaccine&#39;s benefits.&nbsp; 
	&nbsp;</li>
	<li>Vaccine Inequality - The unequal distribution of vaccines among low-, middle-, and high-income countries also leads to low vaccination rates in communities.&nbsp; 
	&nbsp;</li>
	<li>Herd Immunity Threshold - Herd immunity can only be achieved if a certain percentage of a population is vaccinated against the disease. This threshold varies depending on the disease. For example, measles requires 95% of the population to be vaccinated while polio requires 80%<a href="#accordion">[5]</a>. 
	&nbsp;</li>
	<li>Mutated Viral Strains - Viruses are constantly mutating and this can give rise to more infectious variants. Moreover, current vaccines may be ineffective against the new variants. Thus, increasing the risk of disease spread. 
	&nbsp;</li>
	<li>Freeloaders - Herd immunity helps protect susceptible individuals, including those who choose not to vaccine themselves. These people are called freeloaders as they benefit from indirect protection but refuse to receive the vaccine. As the proportion of these freeloaders increases in a community, the risk of disease outbreaks also increases due to the loss of herd immunity.&nbsp;&nbsp;</li>
</ul>

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While vaccines are essential to preventing diseases, their efficacy wanes over time. This was evident in a Lancet study that showed decreasing vaccine effectiveness 5-8 months after a second COVID-19 vaccine dose<a href="#reference">6</a>. However, this was more evident in those older than 55 years of age. Moreover, the administration of booster doses restored vaccine effectiveness to levels higher than those seen after the second dose.&nbsp;The emergence of new variants also threatens herd immunity. Boosters such as those against influenza and COVID-19 are updated to include these newer strains. Therefore, boosters are often recommended to help people maintain their level of immunity, especially in the face of new viral mutations.&nbsp;&nbsp;

Conclusion

Although herd immunity can prove beneficial in controlling outbreaks, it does not protect against all vaccine-preventable diseases. For example, since tetanus is spread from the bacteria present in the soil and environment, herd immunity cannot protect you from contracting the disease.&nbsp; 
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Despite the advances in vaccine development and the availability of countless studies on the benefits of vaccines, people remain skeptical about the biological concoction. Community-based education programs can help debunk myths and misconceptions about vaccines and increase uptake, which is a necessary step to achieve herd immunity and controlling disease outbreaks.&nbsp; 
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Nevertheless, vaccines are an important because not only we protect ourselves, but also those around us. Instead of relying on herd immunity, it is best to remain up to date with our vaccinations and educate those around us.&nbsp;

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Key Points

<ul>
	<li>Herd immunity occurs when a proportion of the population becomes immune to a disease. Thus, reducing the spread of the pathogen to others. As a result, susceptible individuals are also protected from the disease. This phenomenon helps protect vulnerable groups in the community that cannot receive vaccines such as the newborns, the elderly, and the immunocompromised individuals.&nbsp;</li>
	<li>Herd immunity can be achieved either through vaccinations or through infection and recovery. However, herd immunity through vaccines is often preferred as it&#39;s more reliable and associated with less risks than natural infection.</li>
	<li>Herd immunity only works against contagious diseases, such as measles, diphtheria, polio, and influenza. Other vaccine-preventable diseases, like tetanus, cannot be controlled by means of herd immunity since they spread through the environment and are not transmitted from person to person.&nbsp;</li>
	<li>The proportion of people required to achieve herd immunity usually varies depending on the disease. This is called the herd immunity threshold.</li>
	<li>Several barriers, such as vaccine hesitancy, the emergence of new disease variants, herd immunity threshold, and an increase in freeloaders can serve as a barrier to achieving herd immunity.</li>
</ul>

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[1] Glatter, K. A. & Finkelman, P., 2021. History of the Plague: An Ancient Pandemic for the Age of COVID-19. The American Journal of Medicine, 134(2), pp. 176-181.

[2] CDC, 2021. History of Smallpox. [Online]

[3] Topley, W. W. C. & Wilson, G. S., 1923. The Spread of Bacterial Infection. The Problem of Herd-Immunity. The Journal of Hygiene, 21(3), pp. 243-249.

[4] Kim, T. H., Johnstone, J. & Loeb, M., 2011. Vaccine herd effect. Scandinavian Journal of Infectious Diseases, 43(9), pp. 683-689.

[5] World Health Organization, 2020. Coronavirus disease (COVID-19): Herd immunity, lockdowns and COVID-19.

[6] Menni, C. et al., 2022. COVID-19 vaccine waning and effectiveness and side-effects of boosters: a prospective community study from the ZOE COVID Study. The Lancet, 22(7), pp. 1002-1010.

Nimrah H. Sattar

Madeeha Syed

This article or video has been vetted and verified by Meri Sehat’s specialists. It contains citations and research from validated sources.

How To Boost Your Immunity, Naturally?

Overview

You don&rsquo;t have to wait until you&rsquo;re sick to eat healthily, you can work pre-emptively to boost your immune system. And eating certain highly nutritious foods can help.&nbsp;

One important note is that no diet alone can prevent or cure you of a disease, but it can help provide relief from some of the symptoms. Along with lifestyle modifications, proper diet, and other changes, certain foods can have an overall positive impact on your health.

Let&rsquo;s take a look at the top five immunity-boosting food items!

top immunity-boosting food

<h5>Citrus Fruits</h5>

Most people turn to Vitamin C when they develop a cold. The reason for this is that it strengthens your immune system. Vitamin C increases the production of white blood cells, which are the main fighters against any infection. Almost all citrus fruits contain Vitamin C.&nbsp;

Oranges, grapefruit, limes, lemons, and tangerines are packed with this essential nutrient.

As your body doesn&rsquo;t store or produce <a href="https://merisehat.pk/article/vitamin-c-lemonade-for-skin">Vitamin C</a> it is essential to meet the daily requirement through your diet. Please note that the average recommended daily dose for women is 75 mg and for men, it is 90 mg. 
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<h5>Spinach</h5>

This is essentially a superfood. Spinach made our list not just because it&rsquo;s <a href="https://merisehat.pk/article/vitamin-c-lemonade-for-skin">high in Vitamin C</a>, but also because it&rsquo;s loaded with beta-carotene and other antioxidants that may help our immune systems fight off infections. It has Vitamin A and other zinc compounds, plus it&rsquo;s low on calories. It is good to eat it raw, to get the maximum benefits out of it. Cook your spinach lightly for easy absorption of Vitamin A and release of other nutrients. 
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<h5>Yogurt</h5>

Fermented foods are rich in Vitamin C, Zinc, and Iron. It is a good idea to add these foods to your diet to improve your gut health. The bacteria used to make yogurt helps in fighting off infections. Try to eat plain yogurt instead of flavored ones, as they are heavily loaded with sugars. Yogurts are a great source of vitamin D. This can help in strengthening the immune system as well as maintain the level of gut-friendly bacteria to improve digestion. 
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<h5>Turmeric</h5>

Otherwise known as haldi in Urdu. Besides adding zing and color to your food, turmeric is known for its anti-inflammatory effects. The main ingredient in turmeric is curcumin and it&rsquo;s known to give turmeric its medicinal properties. It is known to ease chest congestion, and skin burns and helps in making the immune system strong. You may add turmeric to your foods, to eggs, and even to smoothies. 
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<h5>Broccoli</h5>

Broccoli is one of the best foods for boosting immunity because it is a great source of Vitamin C and other antioxidants. It contributes to maintaining cardiovascular health because it has more protein than most veggies. Broccoli&rsquo;s nutritional strength can be preserved by cooking it as little as possible or even better not to cook at all. Some people say steaming is another best option to keep&nbsp; nutrients. 
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<h5>Ginger</h5>

Another food that&rsquo;s often used during illness is ginger. It helps lessen inflammation and is used to soothe sore throats. Ginger might also help in reducing the nauseous feeling that usually comes with a headache. According to some studies, ginger may lessen chronic discomfort and may even have cholesterol-lowering qualities. 
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Bottom Line

To improve the health of your immune system it is important to watch out for other factors too, mainly your diet and nutritional requirement. One needs to make a conscious effort to add immunity-boosting foods to their diet. Pay special attention to the recommended daily doses and serving size. You can also consult a dietitian or a nutritionist to carefully design a plan for you.&nbsp;

Namwer Rao

There are germs and disease-causing microorganisms all around us. There are multiple instances at any given time when a person is vulnerable and falls sick from being exposed to harmful organisms; these encounters prompt illness and, if exacerbated, demise.&nbsp;

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The human body is quite marvelous &ndash; it has developed numerous approaches to shield itself against deadly pathogens known to mankind. Skin, mucus (bodily fluid), and cilia (minute hairs that remove and guide dust particles and other unwanted substances away from the lungs) all work as physical obstructions to stop pathogens from entering the body in any case.&nbsp;

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However, there are situations when a pathogen finds an entrance to harm the body. This offensive attack leads to our body&#39;s previously insusceptible defenses, called the <a href="https://merisehat.pk/article/how-an-over-prescription-of-antibiotics-affects-your-immune-system" target="_blank">immune system</a>, to be set off and the microorganism is attacked. The situation has only 2 outcomes: the pathogen is either eliminated or it survives.&nbsp;

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Understanding Vaccination Schedule in Childhood

Immunizations refer to the administration of vaccines that contain inactive segments of a specific organism (antigen) that sets off a defensive reaction by the body&rsquo;s immune system<a href="#accordion">[5]</a>.&nbsp;

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More recent vaccines contain a prototype or blueprint for creating antigens instead of the actual antigen itself. The human body creates the antigen irrespective of whether the vaccine administered comprises the actual antigen or just the blueprint. This weakened form of the organism does not trigger the illness in the individual receiving the required dose of the immunization; rather, it&rsquo;s sufficient to simply cause the immune system to react, as much as it would have in case of invasion by a real and active microorganism<a href="#accordion">[5]</a>.&nbsp;

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A few immunizations require more than a single dose, separated by weeks or months. This is done keeping in mind that the body needs some time to create enduring antibodies and develop memory cells. This is how the body prepares to battle that particular sickness-causing entity; based on the memory of this battle, the body is then able to respond to it immediately&nbsp; in case of future exposure<a href="#accordion">[5]</a>. 
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While vaccinations are necessary and vitally important to sustain a healthy and functioning human being, all the required doses are not given to an infant right after birth. To ensure that the fragile and developing body of a newborn baby is not overwhelmed, they are strategically spaced out on a medically approved and suggested timeline to make certain that no dose is missed<a href="#accordion">[2]</a>.&nbsp;

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Note: As a new parent, you should not fret. This article will elaborate the recommended vaccination schedule for your ease. However, it&rsquo;s imperative that you do not skip your appointments before and after the birth of your child and consult your pediatrician&nbsp; about the vaccines that your little one should be receiving.&nbsp; 
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For infants, breast milk is great to build a strong immune system and protect them against numerous infections. Nonetheless, after weaning is complete, this resistance wears off gradually. Then there are some parents who either choose not to breastfeed or are unable to rely on breastfeeding.&nbsp;

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Regardless of whether the kid has been breastfed or not, vaccines are needed to help safeguard them from illness.&nbsp;

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Hepatitis B is the principal vaccine most children receive immediately after birth. It is allowed within the first 24 hours of birth<a href="#accordion">[1]</a>. Because the vaccine is divided into three doses, your child will get a second dose of hepatitis B immunization when they are older, around 1-2 months old. The third dose is administered when they are between 6 and 18 months old<a href="#accordion">[1]</a>.

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Hepatitis B vaccine is chosen to be given first because of the rampant endemic the infection has caused in most parts of the world. Furthermore, individuals who are infected with hepatitis B as a child have a 90% possibility of developing chronic complications, such as liver disease, later in life. In addition to that, since individuals may not realize they have been contaminated, they might spread the infection on the off chance that they come in close contact with your child. Hence, immunization is a safe, extremely effective method for eradicating that hazard immediately by shielding children from infection<a href="#accordion">[1]</a>. 
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At this stage, the child has developed a certain extent of immunity, and to strengthen the shield, they are provided with vaccines that guard them against 7 common and severe diseases. These include<a href="#accordion">[1][2][4]</a>:

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1. DTaP Vaccine

This is a medical acronym to merge 3 major vaccines:

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(a) Diphtheria: This disease starts as a mild sore throat infection, weakness, consistent fever, and swollen glands. If it perseveres, complications can result in uncontrollable swelling of the heart muscle, which leads to heart failure. It can also cause coma, paralysis, or death.

(b) Tetanus: It is caused by a particular bacterium that secretes toxins and increases muscle contractions and stiffness. Individuals can face difficulty in swallowing and experience pain in jaw movement. There is also abdominal pain to deal with. Complications include chronic fever, repeated bone fractures, difficulties in breathing, and death.

(c) Pertussis: This vaccine fights against pertussis or whooping cough. This illness is characterized by a chronic cough, consistent runny nose, and sleep apnea which is a breathing difficulty commonly observed in infants. Complications could lead to pneumonia or death.

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DTaP requires 5 doses which are managed over a wide age span from 2 months to 6 years old. 
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2. Haemophilus Influenzae Type B (Hib) Vaccine

This requires 4 doses that are received by the individual at different stages, starting from 2 months followed by two more shots at 4 months and 6 months respectively. The final dose is at 12-15 months. This vaccine is exceptionally important as it creates immunity against several infections that can be either life-threatening or life-altering such as severe ear infections, pneumonia, epiglottis, and meningitis. If infants have not received their dose and exhibit symptoms, then may need to undergo a spinal tap for confirmation of the presence of the bacterium.

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3. Polio Vaccine

This vaccine also requires 4 doses and is administered via oral drops. The first dose is given at 2 months which is succeeded by the second dose 2 months later. The penultimate dose is received between a span of 6-18 months and the final dose is when the toddler has reached 4 years of age. Polio is an extremely debilitating illness that causes paralysis and sometimes death. Pakistan has been striving rigorously to eradicate polio, which is why in Pakistan, the first dose is given at birth, while the rest of the doses follow a similar global timeline. 
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4. Pneumococcal (PCV13) Vaccine

The PCV13 vaccine follows a similar pathway where 4 four doses are well-distributed over the span of a year, the first year to be exact. The vaccine is imperative to build resistance against Streptococcus pneumonia, which causes respiratory infections and pneumonia. It can also affect the bloodstream causing sepsis or the covering around the brain and spinal cord that may trigger meningitis.&nbsp; 
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5. Rotavirus (RV) Vaccine

Unlike other vaccines provided to children of similar age, the RV can be received through 2 or 3 doses, with the first dose at 2 months, the second at 4 months, and the last dose at 6 months. This is the focal preventive vaccine against diarrhea. The spread of the rotavirus can cause extreme abdominal pain, recurrent vomiting, watery diarrhea, and high-grade fever. In severe cases, it can lead to severe dehydration and ultimately death.&nbsp; 
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Influenza (flu) or the seasonal flu virus immunization is suggested for everybody, starting with those who are 6 months old. Whenever your kid gets first seasonal influenza immunization, they require the second dose a month after the initial dose. Managing symptoms of flu is seldom troublesome, but as common as the virus is, it has a debilitating effect on a person&rsquo;s strength and immune system. It can, therefore, send several healthy kids to the hospital. Seasonal infections change from one year to another; the evolving nature of the pathogen necessitates that everyone gets influenza shot every year. These annual influenza shots allow children to remain healthy and ward off any serious illness<a href="#accordion">[2]</a>. 
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1.&nbsp;Measles-Mumps-Rubella (MMR) Vaccine

The MMR vaccine has been divided into 2 doses (12-15 months and 4-6 years). It is one of the most effective vaccines, offering life long immunity against the following targeted diseases<a href="#accordion">[2]</a>:&nbsp;

&nbsp;

(a) Measles: Measles is responsible for causing irritating rashes, high-grade fever, chronic cough, runny nose, and pink eye. If left unattended, it can cause complications, like encephalitis (inflammation of the brain), pneumonia (infection in the lungs), and even death.

(b) Mumps: This vaccine protects a toddler against mumps, a disease that is characterized by swollen salivary glands that are located under the jaw, fever, consistent headaches, muscle spasms, and fatigue.

(c) Rubella: Rubella is symptomatic with associated symptoms such as rashes, fevers, and swollen lymph nodes. They are more severe in women who are expecting and can increase the risk of miscarriages, stillbirth, premature delivery, and other birth defects.

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An infant&rsquo;s or a budding toddler&rsquo;s follow-up on their first birthday is important as it allows the doctor to schedule visits for the mentioned vaccines. 
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2. Varicella Vaccine

This vaccine can be regarded as the medical fraternity&rsquo;s safeguard against chickenpox. The virus is prevented from infecting the body after the individual receives 2 doses duly, the first is when the child is 12-15 months old and the next dose is between the ages of&nbsp; 4-6<a href="#accordion">[1]</a>. 
&nbsp;

3. Hepatitis A Vaccine

Hepatitis A vaccine can provide an individual with immunity from serious and complicated infections. This vaccine is divided into 2 doses as well, the first shot scheduled at 12 months of age and the second dose is administered 6 months later<a href="#accordion">[4]</a>. Hepatitis A can cause jaundice during which the skin appears to be yellow and other symptoms include stomach pain, shrinking appetite, and fatigue. The infection can further lead to liver failure, arthralgia (joint pain), and kidney, pancreatic, and blood disorders. 
&nbsp;

The COVID-19 pandemic brought with it unprecedented challenges, defying the universal rules of medicine. The new vaccine offered protection to an unmeasurable extent for those who were unable to handle the severity of the virus.

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However, recent strains such as Delta, Omni, etc., have proven to be quite powerful and can weaken the state of the immune system regardless of the type of vaccine. Therefore, it&rsquo;s recommended that people take an extra dose or booster shots following the initial course of that vaccine.

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Anyone who has completed the dual round of vaccine shots of Pfizer or Moderna, and is above the age of 12, is eligible for a booster shot after every 6 months<a href="#accordion">[3]</a>.&nbsp; 
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Vaccines are powerful synthetic defense mechanisms, developed solely to prevent individuals from contracting life-threatening or debilitating infections. Vaccines protect those who receive them. If the majority of the individuals in a community get vaccinated, then it effectively reduces the chance of the virus spreading amongst those who can&rsquo;t receive vaccines. This concept is called herd immunity.

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If anyone has any doubts, then they should immediately refer to a doctor and ask them questions to get authentic information. Because a delay in prevention would only cause an individual to inch closer to a diagnosis.&nbsp; 
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