NewsDay (Zimbabwe)

Facts about COVID-19 vaccines


AS most African countries roll out COVID-19 vaccinatio­ns, there has been many questions on how vaccines work and what they seek to achieve. Below are some simple explanatio­ns to commonly asked questions:

What is vaccinatio­n

Vaccinatio­n is a simple, safe, and effective way of protecting people against harmful diseases before they come into contact with them. It uses your body’s natural defences to build resistance to specific infections and makes your immune system stronger.

Vaccines train your immune system to create antibodies, just as it does when it’s exposed to a disease.

However, because vaccines contain only killed or weakened forms of germs like viruses or bacteria, they do not cause the disease or put you at risk of its complicati­ons.

Most vaccines are given by an injection, but some are given orally (by mouth) or sprayed into the nose. Why is vaccinatio­n important? Vaccinatio­n is a safe and effective way to prevent disease and save lives — now more than ever.

Today there are vaccines available to protect against at least 20 diseases, such as diphtheria, tetanus, pertussis, influenza and measles.

Together, these vaccines save the lives of up to three million people every year.

When we get vaccinated, we aren’t just protecting ourselves, but also those around us.

Some people, like those who are seriously ill, are advised not to get certain vaccines — so they depend on the rest of us to get vaccinated and help reduce the spread of disease.

During the COVID-19 pandemic, vaccinatio­n continues to be critically important.

The pandemic has caused a decline in the number of children receiving routine immunisati­ons, which could lead to an increase in illness and death from preventabl­e diseases.

The World Health Organisati­on (WHO) has urged countries to ensure that essential immunisati­on and health services continue, despite the challenges posed by COVID-19

How does a vaccine work?

Vaccines reduce risks of getting a disease by working with your body’s natural defences to build protection.

When you get a vaccine, your immune system responds.

Recognises the invading germ, such as the virus or bacteria.

Produces antibodies. Antibodies are proteins produced naturally by the immune system to fight disease.

Remembers the disease and how to fight it.

If you are then exposed to the germ in the future, your immune system can quickly destroy it before you become unwell.

The vaccine is, therefore, a safe and clever way to produce an immune response in the body, without causing illness.

Our immune systems are designed to remember.

Once exposed to one or more doses of a vaccine, we typically remain protected against a disease for years, decades or even a lifetime.

This is what makes vaccines so effective. Rather than treating a disease after it occurs, vaccines prevent us in the first instance from getting sick.

How do vaccines protect individual­s and communitie­s?

Vaccines work by training and preparing the body’s natural defences — the immune system — to recognise and fight off viruses and bacteria. If the body is exposed to those disease-causing pathogens later, it will be ready to destroy them quickly — which prevents illness.

When a person gets vaccinated against a disease, their risk of infection is also reduced — so they’re also less likely to transmit the virus or bacteria to others. As more people in a community get vaccinated, fewer people remain vulnerable, and there is less possibilit­y for an infected person to pass the pathogen on to another person. Lowering the possibilit­y for a pathogen to circulate in the community protects those who cannot be vaccinated (due to health conditions, like allergies, or their age) from the disease targeted by the vaccine.

“Herd immunity”, also known as “population immunity” is the indirect protection from an infectious disease that happens when immunity develops in a population either through vaccinatio­n or through previous infection. Herd immunity does not mean unvaccinat­ed or individual­s who have not previously been infected are themselves immune.

Instead, herd immunity exists when individual­s who are not immune, but live in a community with a high proportion of immunity, have a reduced risk of disease as compared to non-immune individual­s living in a community with a small proportion of immunity.

In communitie­s with high immunity, the non-immune people have a lower risk of disease than they otherwise would, but their reduced risk results from the immunity of people in the community in which they are living (that is herd immunity) not because they are personally immune. Even after herd immunity is first reached and a reduced risk of disease among unimmunise­d people is observed, this risk will keep falling if vaccinatio­n coverage continues to increase. When vaccine coverage is very high, the risk of disease among those who are non-immune can become similar to those who are truly immune.

WHO supports achieving “herd immunity” through vaccinatio­n, not by allowing a disease to spread through a population, as this would result in unnecessar­y cases and deaths.

For COVID-19, a new disease causing a global pandemic, many vaccines are in developmen­t and some are in the early phase of rollout, having demonstrat­ed safety and efficacy against disease. The proportion of the population that must be vaccinated against COVID-19 to begin inducing herd immunity is not known. This is an important area of research and will likely vary according to the community, the vaccine, the population­s prioritise­d for vaccinatio­n, and other factors.

Herd immunity is an important attribute of vaccines against polio, rotavirus, pneumococc­us, Haemophilu­s influenzae type B, yellow fever, meningococ­cus and numerous other vaccine preventabl­e diseases. Yet it is an approach that only works for vaccine-preventabl­e diseases with an element of person-to-person spread. For example, tetanus is caught from bacteria in the environmen­t, not from other people, so those who are unimmunise­d are not protected from the disease even if the rest of the community is vaccinated.

Why should I get vaccinated

Without vaccines, we are at risk of serious illness and disability from diseases like measles, meningitis, pneumonia, tetanus and polio. Many of these diseases can be life-threatenin­g. WHO estimates that vaccines save between two and three million lives every year.

Although some diseases may have become uncommon, the germs that cause them continue to circulate in some or all parts of the world. In today’s world, infectious diseases can easily cross borders, and infect anyone who is not protected

Two key reasons to get vaccinated are to protect ourselves and to protect those around us. Because not everyone can be vaccinated — including very young babies, those who are seriously ill or have certain allergies — they depend on others being vaccinated to ensure they are also safe from vaccine-preventabl­e diseases.

How are vaccines developed and tested?

The most commonly used vaccines have been around for decades, with millions of people receiving them safely every year. As with all medicines, every vaccine must go through extensive and rigorous testing to ensure it is safe before it can be introduced in a country.

An experiment­al vaccine is first tested in animals to evaluate its safety and potential to prevent disease. It is then tested in human clinical trials, in three phases:

In phase I, the vaccine is given to a small number of volunteers to assess its safety, confirm it generates an immune response, and determine the right dosage.

In phase II, the vaccine is usually given hundreds of volunteers, who are closely monitored for any side effects, to further assess its ability to generate an immune response. In this phase, data are also collected whenever possible on disease outcomes, but usually not in large enough numbers to have a clear picture of the effect of the vaccine on disease. Participan­ts in this phase have the same characteri­stics (such as age and sex) as the people for whom the vaccine is intended. In this phase, some volunteers receive the vaccine and others do not, which allows comparison­s to be made and conclusion­s drawn about the vaccine.

In phase III, the vaccine is given to thousands of volunteers – some of whom receive the investigat­ional vaccine, and some of whom do not, just like in phase II trials. Data from both groups is carefully compared to see if the vaccine is safe and effective against the disease it is designed to protect against.

Once the results of clinical trials are available, a series of steps is required, including reviews of efficacy, safety, and manufactur­ing for regulatory and public health policy approvals, before a vaccine may be introduced into a national immunisati­on programme.

Following the introducti­on of a vaccine, close monitoring continues to detect any unexpected adverse side effects and further assess effectiven­ess in the routine use setting among even larger numbers of people to continue assessing how best to use the vaccine for the greatest protective impact.

What is in a vaccine?

All the ingredient­s of a vaccine play an important role in ensuring a vaccine is safe and effective. Some of these include:

The antigen. This is a killed or weakened form of a virus or bacteria, which trains our bodies to recognise and fight the disease if we encounter it in the future.

Adjuvants, which help to boost our immune response. This means they help vaccines to work better.

Preservati­ves, which ensure a vaccine stays effective.

Stabiliser­s, which protect the vaccine during storage and transporta­tion.

Vaccine ingredient­s can look unfamiliar when they are listed on a label. However, many of the components used in vaccines occur naturally in the body, in the environmen­t, and in the foods we eat. All of the ingredient­s in vaccines – as well as the vaccines themselves - are thoroughly tested and monitored to ensure they are safe.

 ??  ?? Most vaccines are given by an injection, but some are given orally
Most vaccines are given by an injection, but some are given orally
 ??  ?? WHO estimates that vaccines save between two and three million lives every year
WHO estimates that vaccines save between two and three million lives every year

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