VACCINE SAFET

Vaccines are safe and effective. Because vaccines are given to millions of healthy people - including children — to prevent serious diseases, they're held to very high safety standards.

In this section, you'll learn more about vaccine safety — and get answers to common questions about vaccine side effects.

How are vaccines tested for safety?

Every licensed and recommended vaccine goes through years of safety testing including: Testing and evaluation of the vaccine before it's licensed by the Central Drugs Standard Control Organization(CDSCO) and recommended for use by the Drug Controller General of India (DCGI)

Monitoring the vaccine's safety after it is recommended for infants, children, or ad

Vaccines are tested before they're recommended for use

Before a vaccine is ever recommended for use, it's tested in labs. This process can take several years. CDSCO & DCGI uses the information from these tests to decide whether to test the vaccine with people.

During a clinical trial, a vaccine is tested on people who volunteer to get vaccinated. Clinical trials start with 20 to 100 volunteers, but eventually include thousands of volunteers. These tests take several years and answer important questions like:

Is the vaccine safe?
What dose (amount) works best?
How does the immune system react to it?

Throughout the process, CDSCO & DCGI works closely with the company producing the vaccine to evaluate the vaccine's safety and effectiveness. All safety concerns must be addressed before CDSCO & DCGI licenses a vaccine.

Vaccines are monitored after they're recommended to the public

Once a vaccine is licensed and recommended for use, CDSCO, DCGI , and other State agencies continue to monitor its safety.

VACCINE SIDE EFFECTS

Most people don't have any serious side effects from vaccines. The most common side effects — like soreness where the shot was given — are usually mild and go away quickly on their own.

What are common side effects of vaccines?

The most common side effects after vaccination are mild. They include:
Pain, swelling, or redness where the shot was given
Mild fever
Chills
Feeling tired
Headache
Muscle and joint aches

Most common side effects are a sign that your body is starting to build immunity (protection) against a disease.

What about serious side effects?

Serious side effects from vaccines are extremely rare. For example, if 1 million doses of a vaccine are given, 1 to 2 people may have a severe allergic reaction. Keep in mind that getting vaccinated is much safer than getting the diseases vaccines prevent.

What if I feel sick after getting vaccinated?

Talk with your doctor if you're concerned about your health after getting vaccinated. In the very rare event that a vaccine causes a serious problem you may can contact CDSCO, DCGI , and other State agencies

VACCINES WORK

Vaccines are very effective — and they're the best protection against many serious diseases. Most people who get vaccinated will have immunity (protection) against the disease.

How do we know that vaccines work?

Before a vaccine is recommended for use in India, the CDSCO & DCGI makes sure that it works — and that it's safe.

Since vaccines were invented, the number of babies and adults who get sick or die from vaccine-preventable diseases has gone way down — and some diseases have been wiped out altogether in India.

If we didn't have vaccines, would clean water and modern hygiene prevent these diseases anyway?

No. Clean water and good personal, home, and public hygiene (cleaning practices) help slow down or stop some germs from spreading, but they don't get rid of diseases. Some diseases — especially respiratory diseases that spread through the air, like measles —are more difficult to prevent.

The bottom line is that as long as diseases are around, people will continue to get sick. And that's why it's so important to get vaccinated. 

VACCINES PROTECT YOU

Vaccines do an incredible job of protecting you from serious diseases like whooping cough and measles.

Have you ever wondered how vaccines actually work? Vaccines help your immune system do its job better and faster. And that protects you from serious diseases.

What is the immune system?

The immune system is a network of cells, tissues, and organs that work together to defend the body from harmful germs. When bacteria, viruses, and other germs invade your body, they multiply and attack. This invasion is called an infection. Infections cause the diseases that make you sick. Your immune system protects you from the disease by fighting off the invading germs.

How does the immune system work?

Your immune system is always on patrol in your body. When it comes across an invading germ, it attacks that germ. This is called an immune response.

Here's how an immune response works:

Your immune system sounds the alarm so your body knows there's an infection.
It begins releasing antibodies to fight the germ — think of antibodies as soldiers designed to fight off the specific germ you have. This process can take a few days.
The antibodies work to attack, weaken, and destroy the germ.
Afterwards, your immune system remembers the germ. If the germ invades again, your body can recognize it and quickly send out the right antibodies so you don't get sick!
This protection against a certain disease is called immunity. In many cases, immunity lasts your whole life.

How do vaccines work?

Vaccines help your immune system fight infections faster and more effectively. When you get a vaccine, it sparks your immune response, helping your body fight off and remember the germ so it can attack it if the germ ever invades again. And since vaccines are made of very small amounts of weak or dead germs, they won't make you sick. Vaccines often provide long-lasting immunity to serious diseases without the risk of serious illness.

Which is safer: Natural immunity or immunity after getting a vaccine?

Vaccines are much safer. Natural immunity happens after you get sick with a disease. But diseases can be serious — and even deadly. A vaccine protects you from a disease before it makes you sick.

VACCINES PROTECT YOUR COMMUNITY

Did you know that when you get vaccinated, you're protecting yourself and your community? This concept is called community immunity, or herd immunity. And it's an important reason for you and your family to get vaccinated — so you can help keep yourselves and your community healthy.

How does community immunity work?

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, the germs can't travel as easily from person to person — and the entire community is less likely to get the disease.

That means even people who can't get vaccinated will have some protection from getting sick. And if a person does get sick, there's less chance of an outbreak because it's harder for the disease to spread. Eventually, the disease becomes rare — and sometimes, it's wiped out altogether.

Who does community immunity protect?

Community immunity protects everyone. But it's especially important because some people can't get vaccinated for certain diseases — such as people with some serious allergies and those with weakened or failing immune systems (like people who have cancer, HIV/AIDS, type 1 diabetes, or other health conditions).

Community immunity is also important for the very small group of people who don't have a strong immune response from vaccines.

If vaccines have wiped out some diseases in India, can we stop getting vaccinated for them?

No. Many vaccine-preventable diseases that we don't see much in the United States still make people sick in other countries. So it's possible for travelers to bring these diseases back to the India, where they could then spread. If we stop getting vaccinated, we won't be protected from these diseases — community immunity protects us only if enough people continue to get vaccinated.

If you're traveling outside of India, you may need to get vaccines to keep you healthy and safe.

VACCINE TYPES

There are several different types of vaccines. Each type is designed to teach your immune system how to fight off certain kinds of germs — and the serious diseases they cause.

When scientists create vaccines, they consider:

How your immune system responds to the germ
Who needs to be vaccinated against the germ
The best technology or approach to create the vaccine

Based on a number of these factors, scientists decide which type of vaccine they will make. There are 4 main types of vaccines:

Live-attenuated vaccines
Inactivated vaccines
Subunit, recombinant, polysaccharide, and conjugate vaccines
Toxoid vaccines

Live-attenuated vaccines

Live vaccines use a weakened (or attenuated) form of the germ that causes a disease

Because these vaccines are so similar to the natural infection that they help prevent, they create a strong and long-lasting immune response. Just 1 or 2 doses of most live vaccines can give you a lifetime of protection against a germ and the disease it causes.

But live vaccines also have some limitations. For example:

Because they contain a small amount of the weakened live virus, some people should talk to their health care provider before receiving them, such as people with weakened immune systems, long-term health problems, or people who've had an organ transplant.

They need to be kept cool, so they don't travel well. That means they can't be used in countries with limited access to refrigerators.

Live vaccines are used to protect against:

Measles, mumps, rubella (MMR combined vaccine)
Rotavirus
Smallpox
Chickenpox
Yellow fever

Inactivated vaccines

Inactivated vaccines use the killed version of the germ that causes a disease. Inactivated vaccines usually don't provide immunity (protection) that's as strong as live vaccines. So you may need several doses over time (booster shots) in order to get ongoing immunity against diseases.

Inactivated vaccines are used to protect against:

Hepatitis A
Flu (shot only)
Polio (shot only)
Rabies

Subunit, recombinant, polysaccharide, and conjugate vaccines

Subunit, recombinant, polysaccharide, and conjugate vaccines use specific pieces of the germ — like its protein, sugar, or capsid (a casing around the germ).

Because these vaccines use only specific pieces of the germ, they give a very strong immune response that's targeted to key parts of the germ. They can also be used on almost everyone who needs them, including people with weakened immune systems and long-term health problems.

One limitation of these vaccines is that you may need booster shots to get ongoing protection against diseases.

These vaccines are used to protect against:

Hib (Haemophilus influenzae type b) disease
Hepatitis B
HPV (Human papillomavirus)
Whooping cough (part of the DTaP combined vaccine)
Pneumococcal disease
Meningococcal disease
Shingles

Toxoid vaccines

Toxoid vaccines use a toxin (harmful product) made by the germ that causes a disease. They create immunity to the parts of the germ that cause a disease instead of the germ itself. That means the immune response is targeted to the toxin instead of the whole germ.

Like some other types of vaccines, you may need booster shots to get ongoing protection against diseases.

Toxoid vaccines are used to protect against:

Diphtheria 
Tetanus

The future of vaccines

Did you know that scientists are still working to create new types of vaccines? Here are 2 exciting examples:

DNA vaccines are easy and inexpensive to make — and they produce strong, long-term immunity.

Recombinant vector vaccines (platform-based vaccines) act like a natural infection, so they're especially good at teaching the immune system how to fight germs.

VACCINE INGREDIENTS

Today's vaccines use only the ingredients they need to be safe and effective.

Each ingredient in a vaccine serves a specific purpose. For example, vaccine ingredients may:

Help provide immunity (protection) against a specific disease
Help keep the vaccine safe and long lasting
Be used during the production of the vaccine

Ingredients provide immunity

Vaccines include ingredients to help your immune system respond and build immunity to a specific disease. For example:

Antigens are very small amounts of weak or dead germs that can cause diseases. They help your immune system learn how to fight off infections faster and more effectively. The flu virus is an example of an antigen.
Adjuvants, which are in some vaccines, are substances that help your immune system respond more strongly to a vaccine. This increases your immunity against the disease. Aluminum is an example of an adjuvant.

Ingredients keep vaccines safe and long lasting

Some ingredients help make sure a vaccine continues to work like it's supposed to and that it stays free of outside germs and bacteria. For example:

Preservatives, like thimerosal, protect the vaccine from outside bacteria or fungus. Today, preservatives are usually only used in vials (containers) of vaccines that have more than 1 dose. That's because every time an individual dose is taken from the vial, it's possible for harmful germs to get inside. Most vaccines are also available in single-dose vials and do not have preservatives in them.

Stabilizers, like sugar or gelatin, help the active ingredients in vaccines continue to  work while the vaccine is made, stored, and moved. Stabilizers keep the active ingredients in vaccines from changing because of something like a shift in temperature where the vaccine is being stored.

Ingredients are used during the production of vaccines

Some ingredients that are needed to produce the vaccine are no longer needed for the vaccine to work in a person.

These ingredients are taken out after production so only tiny amounts are left in the final product. The very small amounts of these ingredients that remain in the final product aren't harmful.

Examples of ingredients used in some vaccines include:

Cell culture (growth) material, like eggs, to help grow the vaccine antigens.
Inactivating (germ-killing) ingredients, like formaldehyde, to weaken or kill viruses, bacteria, or toxins in the vaccine.
Antibiotics, like neomycin, to help keep outside germs and bacteria from growing in the vaccine.

Common questions about vaccine ingredients

Learn more about the types of vaccine ingredients and why they're used from the common questions below.

Can vaccines with thimerosal cause mercury poisoning?

A: No. Thimerosal has a different form of mercury (ethylmercury) than the kind that causes mercury poisoning (methylmercury). It's safe to use ethylmercury in vaccines because it's less likely to build up in the body — and because it's used in very, very small amounts. Even so, most vaccines do not have any thimerosal in them. If you're concerned about thimerosal or mercury in vaccines, talk with your doctor.

Can people who are allergic to antibiotics get vaccinated?

A: Yes. However, if you have an allergy to antibiotics, it's a good idea to talk with your doctor about getting vaccinated. But in general, antibiotics that people are most likely to be allergic to — like penicillin — aren't used in vaccines.

Can people with egg allergies get vaccinated?

A: Yes. People with egg allergies can get any licensed, recommended flu vaccine that's appropriate for their age. They no longer have to be watched for 30 minutes after getting the vaccine. People who have severe egg allergies should be vaccinated in a medical setting and be supervised by a health care professional who can recognize and manage severe allergic conditions.

Is the formaldehyde used in some vaccines dangerous?

A: No. If formaldehyde is used to help produce a vaccine, only very small amounts are left in the final product. This amount is so small that it's not dangerous — in fact, there's actually more formaldehyde found naturally in our bodies than there is in vaccines made with formaldehyde.

Is the aluminum used in some vaccines dangerous?

A: No. Vaccines made with aluminum have only a very small amount of aluminum in them. For decades, vaccines that include aluminum have been tested for safety — these studies have shown that using aluminum in vaccines is safe.