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Vaccines | Immunization | Inoculation

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What are vaccines?

Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach your body's immune system to recognize and defend against harmful germs. For example, there are vaccines to protect against diseases caused by:

• Viruses, like the ones that cause the flu and COVID-19
• Bacteria, including tetanus, diphtheria, and pertussis

What are the types of vaccines?

There are several types of vaccines:

• Live-attenuated vaccines use a weakened form of the germ.
• Inactivated vaccines use a killed version of the germ.
• Subunit, recombinant, polysaccharide, and conjugate vaccines use only specific pieces of the germ, such as its protein, sugar, or casing.
• Toxoid vaccines that use a toxin (harmful product) made by the germ.
• mRNA vaccines use messenger RNA, which gives your cells instructions for how to make a protein (or piece of a protein) of the germ.
• Viral vector vaccines use genetic material, which gives your cells instructions for making a protein of the germ. These vaccines also contain a different, harmless virus that helps get the genetic material into your cells.

Vaccines work in different ways, but they all spark an immune response. The immune response is the way your body defends itself against substances it sees as foreign or harmful. These substances include germs that can cause disease.

What happens in an immune response?

There are different steps in the immune response:

• When a germ invades, your body sees it as foreign.
• Your immune system helps your body fight off the germ.
• Your immune system also remembers the germ. It will attack the germ if it ever invades again. This "memory" protects you against the disease that the germ causes. This type of protection is called immunity.

What are immunization and vaccination?

Immunization is the process of becoming protected against a disease. But it can also mean the same thing as vaccination, which is getting a vaccine to become protected against a disease.

Why are vaccines important?

Vaccines are important because they protect you against many diseases. These diseases can be very serious. So getting immunity from a vaccine is safer than getting immunity by being sick with the disease. And for a few vaccines, getting vaccinated can actually give you a better immune response than getting the disease would.

But vaccines don't just protect you. They also protect the people around you through community immunity.

What is community immunity?

Community immunity, or herd immunity, is the idea that vaccines can help keep communities healthy.

Normally, germs can travel quickly through a community and make a lot of people sick. If enough people get sick, it can lead to an outbreak. But when enough people are vaccinated against a certain disease, it's harder for that disease to spread to others. This type of protection means that the entire community is less likely to get the disease.

Community immunity is especially important for people who can't get certain vaccines. For example, they may not be able to get a vaccine because they have weakened immune systems. Others may be allergic to certain vaccine ingredients. And newborn babies are too young to get some vaccines. Community immunity can help to protect them all.

Are vaccines safe?

Vaccines are safe. They must go through extensive safety testing and evaluation before they are approved in the United States.

What is a vaccine schedule?

A vaccine, or immunization, schedule lists which vaccines are recommended for different groups of people. It includes who should get the vaccines, how many doses they need, and when they should get them. In the United States, the Centers for Disease Control and Prevention (CDC) publishes the vaccine schedule.

It's important for both children and adults to get their vaccines according to the schedule. Following the schedule allows them to get protection from the diseases at exactly the right time.

• Get Vaccines to Protect Your Health (Adults Ages 19 to 49) (Office of Disease Prevention and Health Promotion) Also in Spanish
• Recommended Adult Immunization Schedule for ages 19 years or older, United States, 2019 (Centers for Disease Control and Prevention)
• Understanding How Vaccines Work (Centers for Disease Control and Prevention)
• Vaccine Basics (Department of Health and Human Services)
• Vaccines for Adults (Mayo Foundation for Medical Education and Research) Also in Spanish

• Screening Checklist for Contraindications to Vaccines for Adults (Immunization Action Coalition) - PDF Also in Spanish

• Heart Disease, Stroke, or Other Cardiovascular Disease and Adult Vaccination (Centers for Disease Control and Prevention) Also in Spanish
• HIV Infection and Adult Vaccination (Centers for Disease Control and Prevention)
• Keeping Your Vaccine Records up to Date (Centers for Disease Control and Prevention) Also in Spanish
• Liver Disease and Adult Vaccination (Centers for Disease Control and Prevention)
• Vaccinations and Flu Shots for People with Cancer (American Cancer Society) Also in Spanish
• Vaccinations for Adults with Diabetes (Immunization Action Coalition) - PDF
• Vaccine Safety: MedlinePlus Health Topic (National Library of Medicine) Also in Spanish
• Vaccines Protect Your Community (Department of Health and Human Services) Also in Spanish
• Weakened Immune System and Adult Vaccination (Centers for Disease Control and Prevention)
• What's in Vaccines? (Centers for Disease Control and Prevention)

• Current Vaccine Shortages and Delays (Centers for Disease Control and Prevention)
• There Are Vaccines You Need as an Adult (Centers for Disease Control and Prevention) Also in Spanish
• Travelers' Health: Destinations (Centers for Disease Control and Prevention)
• Vaccines. gov (Department of Health and Human Services) Also in Spanish
• Who Should Not Get Vaccinated with These Vaccines? (Centers for Disease Control and Prevention)

• Vaccine-Preventable Disease Photos (Immunization Action Coalition)

• Adult Vaccine Assessment Tool (Centers for Disease Control and Prevention) Also in Spanish

• Research: Vaccines (National Institute of Allergy and Infectious Diseases)
• Safeguarding Our Health: Vaccines Protect Us All (National Institutes of Health) Also in Spanish
• VaxView: Vaccination Coverage [data] in the U. S. (Centers for Disease Control and Prevention)

• ClinicalTrials.gov: Vaccines (National Institutes of Health)

• Article: Improving timeliness and completion of infant vaccination among infants in Nigerian. ..
• Article: Vaccine efficacy trials for Crimean-Congo haemorrhagic fever: Insights from modelling different...
• Article: Serious adverse events of special interest following mRNA COVID-19 vaccination in. ..
• Vaccines -- see more articles

• Glossary of Vaccine Terms (Centers for Disease Control and Prevention)
• Overview of the Immune System (National Institute of Allergy and Infectious Diseases)

• Centers for Disease Control and Prevention Also in Spanish
• National Institute of Allergy and Infectious Diseases
• National Vaccine Program (Department of Health and Human Services, Office of Infectious Disease and HIV/AIDS Policy)

• Summary of Maternal Immunization Recommendations (Centers for Disease Control and Prevention) - PDF
• Vaccines and Pregnancy (Organization of Teratology Information Specialists) Also in Spanish
• Vaccines and Pregnancy: 8 Things You Need to Know (Centers for Disease Control and Prevention) Also in Spanish

• Vaccinations and Older Adults (National Institute on Aging)

Vaccines and immunization: What is vaccination?

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• Vaccines and immunization: What is vaccination?

August 30, 2021 | FAQ

Revised August 10, 2021

What is vaccination?

Vaccination is a simple, safe and effective way to protect against diseases before a person comes into contact with their pathogens. Vaccination activates the body's natural defense mechanisms to build resistance to a range of infectious diseases and makes your immune system stronger.

Like diseases, vaccines train the immune system to produce specific antibodies. However, vaccines contain only killed or attenuated forms of the causative agents of a particular disease - viruses or bacteria - that do not lead to the disease and do not create the risk of complications associated with it.

Most vaccines are given by injection, although some are given by mouth. vaccines (given by mouth), and nasal spray vaccines (given through the nose).

What is the principle of the vaccine?

Vaccines reduce the risk of disease by activating natural defense mechanisms to build immunity to the pathogen. Vaccination provokes the body's immune response. Immune system:

• Recognizes pathogens such as viruses or bacteria.
• Starts production of antibodies. Antibodies are proteins naturally produced by the body's immune system to fight disease.
• Remembers the causative agent of the disease in order to fight it in the future. If this pathogen enters the body again, the immune system will quickly destroy it, preventing the development of the disease.

Thus, vaccination is a safe and rational way to induce an immune response in the body without the need to infect it with a particular disease.

Our immune system has a memory. By receiving one or more doses of a vaccine, we are usually protected against a particular disease for many years, decades, or even a lifetime. This is what makes vaccines so effective. Vaccines keep us from getting sick, which is much better than having to treat the disease when it has already begun.

When should I get vaccinated (or have my child vaccinated)?

Vaccines protect us throughout our lives and at any age - from birth, through childhood, through adolescence and into old age. In most countries, people are given vaccination cards that show which vaccinations an adult or child has received and when the next vaccinations are due. It is important that all indicated vaccinations are up to date.

By delaying vaccination, we put ourselves at risk of becoming seriously ill. If we wait until the moment when a vaccine is urgently needed - for example, if an outbreak of a disease has begun - then it may be too late to get the desired effect of vaccination or all the necessary doses of the vaccine.


Why do I need to be vaccinated?

Without vaccination, we are at risk of serious diseases such as measles, meningitis, pneumonia, tetanus and polio. Many of these diseases are life threatening. The WHO estimates that childhood vaccines alone save more than 4 million lives each year.

Although some diseases are becoming less common, their pathogens continue to circulate in some or all regions of the world. In today's world, infectious diseases can easily cross borders and infect anyone who lacks immunity to them.

There are two main reasons to get vaccinated: to protect yourself and to protect others. Since some people, such as newborns and people with serious illnesses or those with certain allergies, may not be vaccinated, their protection against vaccine-preventable diseases depends on the availability of vaccinations in others.

Who should not be vaccinated?

Almost anyone can get vaccinated. However, for people with certain diseases and conditions, some vaccinations are contraindicated or should be deferred to a later date. These diseases and conditions may include:

• chronic diseases or treatments (eg chemotherapy) that suppress the immune system;
• extremely rare acute and life-threatening allergic reactions to vaccine components;
• severe illness at the time of vaccination. However, these children should be vaccinated as soon as they recover. Moderate malaise or subfebrile temperature is not a contraindication for vaccination.

Often these factors need to be considered depending on the type of vaccine. If you are not sure whether you or your child should get a particular vaccine, ask your doctor. Your doctor will help you make an informed decision about your or your child's vaccinations.

What diseases do vaccines protect against?

vaccines protect against a number of diseases, including the following:

• Cervical Cancer
• cholera
• Covid-1
• 9000
• Pertussis
• Pneumonia
• Poliomyelitis
• Rabies
• Rotavirus
• Rubella
• Tetanus
• Typhoid fever
• Varicella
• Yellow fever

A number of vaccines for some other diseases, including Ebola or malaria, are currently under development or experimental use, but these vaccines have not yet been introduced in mass use throughout the world.

Not all vaccinations may be required in your country. Vaccinations against certain diseases may only be required for people who travel to certain countries or who are at increased risk due to their professional activities. Ask your doctor what vaccinations you and your family members need.

Why are vaccinations started at such an early age?

In their daily lives, young children may be in many different places and come into contact with a wide variety of people, thereby being at serious risk of infection. The WHO-recommended immunization schedule allows infants and young children to be protected as early as possible against a range of diseases. Often, infants and young children are most at risk of illness because their immune systems are not yet fully developed and their bodies are less able to fight off infections. Therefore, it is extremely important to vaccinate children according to the recommended schedule.


What is included in the vaccine?

All components of a vaccine play an important role in its safety and effectiveness. The composition of vaccines, in particular, includes the following components:

• Antigen. This is a killed or weakened form of any microorganism - a virus or a bacterium - on which our body learns to recognize and destroy the causative agent of the disease if it encounters it in the future.
• Adjuvants that help enhance the body's immune response. Without them, vaccines would be less effective.
• Preservatives to keep vaccines effective.
• Stabilizers to preserve the vaccine during storage and transport.

The names of vaccine components written on vaccine packages can be confusing. However, many of them are naturally present in the body, environment and food. All of the components of vaccines, like the vaccines themselves, are subject to rigorous testing and monitoring for their safety.

Are vaccines safe?

Vaccination is safe and usually causes minor and temporary side effects, such as arm pain or mild fever. More serious side effects are possible, but they are extremely rare.

Any licensed vaccine is rigorously tested through several phases of clinical trials before it is approved for use and regularly evaluated after introduction. Scientists are also constantly monitoring information from a range of sources for signs that a particular vaccine may pose a health risk.

It must be remembered that the risk of serious harm to health from a vaccine-preventable disease is much greater than the risk associated with vaccination. For example, tetanus can cause severe pain, convulsions and thrombosis, and measles can lead to encephalitis (infection of the brain) and blindness. Many vaccine-preventable diseases can even be fatal. The benefits of vaccination far outweigh the risks, and without vaccines, the world would experience an order of magnitude more illness and death.


My child did not receive the recommended vaccinations on time. Is it too late to get the missing vaccinations?

In most cases, it is never too late to get the missing shots. Ask your doctor how and when you or your child can get the missing shots.

Do vaccines have side effects?

Like all medicines, vaccines can cause mild side effects such as low grade fever and pain or redness at the injection site. These symptoms usually go away on their own within a few days.


Severe or long-term side effects are extremely rare. The chance of experiencing a serious adverse body reaction to a vaccine is 1 in a million.

The safety of vaccines is subject to ongoing monitoring and is continuously monitored for rare adverse reactions.


How are vaccines developed and tested?

The most commonly used vaccines have been in use for decades, and every year millions of people receive them safely. Like all medicines, every vaccine must undergo extensive, rigorous testing to assess its safety before it can be introduced in countries.

Experimental vaccines are first tested in animals to evaluate their safety and ability to prevent disease. They are then tested in human clinical trials, which consist of three phases.

• During the first phase of the trial, the vaccine is given to a small number of volunteers to evaluate its safety, make sure it generates an immune response, and determine the correct dose.

• During the second phase of the trial, the vaccine is typically administered to hundreds of volunteers, who are closely monitored for any side effects and further evaluation of its ability to generate an immune response. Data on disease outcomes are also collected at this stage whenever possible, but these data are usually not sufficient to provide a clear picture of the impact of the vaccine on the disease. Participants in this phase of the trial share the same characteristics (such as age and gender) as the people for whom the vaccine is intended. At this stage, some volunteers receive the vaccine and others do not, allowing comparisons to be made and conclusions about the vaccine to be made.


• During the third phase of the trial, the vaccine is administered to thousands of volunteers, some of whom receive the study vaccine and some do not, as in the second phase of the trial. The data from both groups are carefully compared to determine whether the vaccine is safe and effective in protecting against the disease it is intended to target.

Following clinical trial results, a number of steps must be taken before a vaccine can be included in a national immunization program, including efficacy, safety, and manufacturing reviews for regulatory approval and public health policy approval.

Following the introduction of the vaccine, careful monitoring continues to be carried out to identify any unexpected unwanted side effects and further evaluate its effectiveness under conditions of regular use in even more people, which will allow understanding how to best use the vaccine to ensure the greatest protective effect. For more information on vaccine development and safety, click here.

Can a child have more than one vaccine at a time?

Scientific evidence shows that the simultaneous administration of several vaccines does not have negative consequences. Every day, children are exposed to several hundred foreign substances that trigger the body's immune response. A simple meal is accompanied by the entry of new microorganisms into the body, and many bacteria live in the nose and mouth.


The ability to combine multiple vaccines (such as diphtheria, whooping cough and tetanus) reduces the number of injections and reduces discomfort for the child. In addition, it allows you to know for sure that the child received the right vaccinations at the right time and will not catch a potentially fatal disease.

Is there a link between vaccination and autism?

There is no evidence of any association between vaccination and autism spectrum disorders. This conclusion was drawn from the results of many studies conducted on very large groups of people.


In 1998, a study was published raising concerns about a possible link between the measles, mumps, and rubella (MMR) vaccine and autism, but the study later found a number of serious misrepresentations and falsified information. The journal that published this work later withdrew it, and the doctor who wrote it lost his license to practice medicine. Unfortunately, due to fears caused by this publication, vaccination rates in some countries dropped sharply, which subsequently led to outbreaks of these diseases.

We all have a responsibility to take the necessary steps to disseminate only reliable, science-based information about vaccines and the diseases that vaccines help prevent.

Does my daughter need to be vaccinated against the human papillomavirus (HPV)?

Almost all cases of cervical cancer are caused by sexually transmitted HPV infection. Vaccination against HPV before a person comes into contact with this virus is the most effective means of protection against this disease. Studies in Australia, Belgium, Sweden, Germany, New Zealand, the United Kingdom, the United States of America and Sweden showed that vaccination reduced the number of HPV infections among adolescent girls and young women to almost 90%.


Studies have proven the safety and efficacy of the HPV vaccine. WHO recommends that all girls aged 9–14 years be vaccinated with two doses of the HPV vaccine, and that women be periodically screened for cervical cancer later in life.

I have questions about vaccinations. Who should I contact?

If you have any questions about vaccinations, be sure to ask your doctor. He or she will be able to give you evidence-based information about vaccinations, including the recommended vaccination schedule in your country for you and your family members.

When looking for information about vaccines on the Internet, look only to trusted sources. To help you find these sources, WHO has reviewed and "certified" many websites in many languages ​​around the world to contain only information based on sound scientific evidence and independent analysis by leading technical experts. All of these websites are part of the Vaccine Safety Net (www.vaccinesafetynet.org).

How does WHO contribute to vaccine safety?

WHO works to ensure that all people around the world are protected with safe and effective vaccines. To this end, we help countries build robust vaccine safety systems and apply strict international standards for vaccine regulation.

Together with scientists from around the world, WHO experts continuously monitor to ensure that vaccines are safe. We are also working with partners to assist countries in investigating and reporting potential problems.


Any unexpected side effects reported to WHO are evaluated by an independent panel of experts called the Global Advisory Committee on Vaccine Safety.

Immunizations and vaccines: what is the difference

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Let's get some terminology out of the way. At the household level, many do not feel the difference between serum, vaccine and vaccination, vaccination and immunization - we will try to explain to you the main terms used in vaccine prevention. This article does not claim to be fundamental - it is only a quick reference.

As a primary source of terms, we used queries that are most often typed in search engines on the topic of vaccination: in the search, people usually write in ordinary, conversational language. Here we will try to avoid complex medical terminology, because the article is written for people who are far from medicine.

Vaccination is perhaps the main method of preventing many serious infectious diseases. The essence of the method is the artificial reproduction of the immune response of the human body, so that in the future the antibodies produced themselves fight the infection (it is also called active immunity).

Immunoprophylaxis is a broader concept than vaccination: it can be "specific" and "non-specific". The first means measures against a specific infection - this, in fact, is vaccination. The second implies a much wider range of ways to increase the immunity of the body as a whole, and not just creating a barrier for specific diseases: hardening, quality nutrition, proper rest and work, minimizing stress - in short, everything that helps the body stay healthy. In addition, immunoprophylaxis allows the creation of passive immunity by introducing ready-made antibodies in sera.

Vaccination is essentially the same as vaccination, the difference is purely semantic: the word "vaccination" is shorter and easier to pronounce, although the second term is more correct from the point of view of medical science.

Immunization is the same as immunization.

A vaccine is a medical product that is given to a person to produce active immunity to one or more specific diseases. Please note: we are talking about the "drug", and not about the procedure for using it. Sometimes vaccination is understood as the procedure for administering a vaccine, but we will use the word "vaccination" for this.

Serum and vaccine solve the same tasks - they contribute to the development of acquired immunity organisms. But there is also a fundamental difference between them: the vaccine contains weakened or dead agents of infection, and the serum contains ready-made antibodies against a specific disease. Serum is usually used to fight an already begun disease, that is, it is, in fact, a medicine, not a prophylactic.

Inoculation is the procedure for administering a preparation with antigenic material, i.e. a vaccine or serum. Once again: "vaccine" and "serum" are drugs, "vaccination" is the process of introducing them into the human body. We will adhere to such a division of concepts, but deviations are sometimes possible.

Revaccination is a way to support post-vaccination immunity through repeated vaccinations. Many vaccinations are valid for a limited period, after which the acquired immunity weakens. It is assumed that the primary vaccination has already been carried out, and, based on this, a revaccination schedule is drawn up.

Revaccination is the same as revaccination.

Re-vaccination - the procedure for introducing vaccinations during re-vaccination, that is, during revaccination.

Mandatory vaccination - a list of vaccinations that the state considers necessary: ​​their set and timing are regulated by the National Immunization Schedule. Strictly speaking, there are no mandatory vaccinations in Russia, even children without them are admitted to kindergartens, but only if their parents have officially confirmed their refusal to be vaccinated.

Vaccination schedule - a list and schedule of vaccinations. Usually associated with the concept of mandatory vaccinations and the National Immunization Schedule, but can be used wherever it is required to describe the set and timing of vaccinations, for example, during revaccination.

The vaccination schedule is the same as the vaccination schedule.

Vaccination schedule - the same as the vaccination schedule.

Vaccination 2020 is a combination often found in search queries: people want to know which vaccinations are mandatory for the current year, and what changes have been made to the vaccination calendar.

Inoculation is the same as "inoculation". This is usually written in search queries by those who do not know the difference between a vaccine and an inoculation.

To be vaccinated or vaccinated - "to vaccinate" is a more medical term, an example of professional slang. In everyday life, the word "do" or "do" is usually used. In most cases, we will use the everyday option, but in some more "medical" articles, professional terms are not excluded.

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