Please read the Disclaimer at the end of this page.
INTRODUCTION — Vaccines are one of the most effective ways to prevent serious illness in children and adults. Vaccine programs in the United States have been quite successful in reducing the number of children affected by many highly contagious diseases, including measles, rubella, mumps, diphtheria, and polio.
The following is a discussion of how vaccines work, common side effects, reasons to avoid a particular vaccine, and common concerns about vaccines. Separate articles discuss specific vaccine recommendations for children and adults. (See "Patient education: Vaccines for infants and children age 0 to 6 years (Beyond the Basics)" and "Patient education: Vaccines for children age 7 to 18 years (Beyond the Basics)" and "Patient education: Vaccines for adults (Beyond the Basics)".)
HOW DO VACCINES WORK?
Infection and the immune system — A person's immune system protects them against illness and infection. When a germ (such as a bacterium or virus) gets into the body, it multiplies and attacks the cells; this is what makes people sick. The immune system responds by creating proteins called antibodies to fight the infection and help the person recover.
Antibodies also work to prevent a person from becoming ill in the future. Once a person has antibodies, the next time they are exposed to the germ, their immune system recognizes it and rapidly produces the antibodies required to destroy the germ. This response protects the person from developing the disease. In some cases, this protection lasts for life; for example, a person who had measles as a child is unlikely to get it again, even if they are in close contact with a person who is infected. In other cases, people need to get regular "booster" vaccines to maintain immunity over time.
Vaccines work by stimulating the immune system to produce antibodies, like it would if a person had an infection. However, unlike bacteria and viruses, vaccines do not actually make people sick.
Active versus passive immunity — There are two main types of immunity, active and passive:
●"Active" immunity means a person has antibodies against a particular germ. This can happen if they have had the infection in the past (this is called "natural immunity") or because they have received a vaccine that stimulated the immune system to produce the antibodies. Most vaccines induce active immunity.
●"Passive" immunity comes from serum immune globulin, which provides temporary immunity with antibodies obtained from a large pool of donors. This approach offers short-term protection to people who have been exposed to a specific germ. One example of passive immunization is hepatitis B immune globulin (HBIG). HBIG is given to newborns whose mothers have hepatitis B. HBIG provides temporary protection to the newborn against infection with hepatitis B.
Herd immunity — For diseases that can spread from person to person, the goal of vaccines is to get to "herd immunity." This is when enough people are immune to a disease that it can no longer spread easily. To get to herd immunity, lots of people need to get vaccinated. This helps protect people who cannot get vaccinated for some reason.
Diseases such as diphtheria are uncommon in resource-rich countries such as the United States. However, these illnesses are still common in other parts of the world and can spread when people travel or relocate. Vaccines help reduce the number of people who can spread the infection.
An example of a successful vaccine program is smallpox. Before a vaccine was available, smallpox killed millions of people every year. As a result of an intensive vaccination program, smallpox has been completely eliminated throughout the world.
Types of vaccines — Some vaccines are called "live" vaccines because they are made with a weakened form of the germ; such vaccines should be avoided in certain children with suppressed immunity, as discussed below (see 'Contraindications to live vaccines' below). Other vaccines are made with germs that have been killed or parts of germs.
HOW ARE VACCINES GIVEN? — In children, most vaccines are given in the form of a shot. Vaccines are also given in other ways, such as in a liquid taken by mouth (eg, rotavirus) or as a nasal spray (eg, one form of the influenza vaccine).
VACCINE SAFETY — Many people are concerned about the risks of vaccines. However, vaccines have a long record of being a safe and effective way of preventing disease. Before a vaccine is approved for use, it has to go through a specific process to test it for safety. This involves running "clinical trials" with lots of people who volunteer to try the vaccine. During these trials, researchers study how well the vaccine works and how many people had side effects. The results are reviewed by doctors and other experts who do not work for the drug companies that made the vaccine. These experts must agree that the vaccine is safe and effective enough to be given to the public.
In most cases, the benefits of vaccinating are much greater than the potential risks.
There are a lot of myths about vaccines, and it can be hard to tell what is true and what is false. Here are some important things to know:
●Vaccines work. The number of people who got childhood diseases, like measles or whooping cough, decreased significantly after vaccines for those diseases became available. When there is an outbreak of one of these diseases, it mostly affects people who did not get the vaccine. Sometimes, a person who was vaccinated does get an infection. But when this happens, their illness is usually milder than it would have been if they did not get the vaccine.
●Vaccines do not make you sick. In some cases, vaccines can cause mild side effects like a fever. These side effects are temporary, and they do not mean that the vaccine gave you an infection. In fact, they typically mean that the vaccine is working and your immune system is responding. (See 'Vaccine side effects' below.)
●It is not better to get immunity "naturally." It's true that actually having an infection can protect you from getting it again in the future. But it is not a good idea to try to get infected on purpose for this reason. Even if you are in good health, it is possible to get very sick or even die from some infections. You could also spread the infection to other people who are at risk of getting seriously ill.
●Vaccines do not contain toxic ingredients. Some people worry about certain ingredients found in some vaccines, such as aluminum. But the amount of aluminum in vaccines is so tiny that it cannot harm you.
●Vaccines do not cause autism. After doing many careful studies, scientists have not found any link between vaccines and autism. Many years ago, one very small study said there was a link between autism and vaccines. But that study turned out to be false.
●The timing of vaccines is important. Some parents and caregivers think it helps to delay a child's vaccines or spread them out over a longer time than experts recommend. But doing this can actually have risks. For example, one study found that children who got their first measles-mumps-rubella (MMR) vaccine later than they were supposed to had a higher risk of fever-related seizures after getting the vaccine. It is important to know that the recommended immunization schedule has been carefully studied, and some vaccines are most effective when given to children at a particular age. (See 'Recommended immunizations for children' below.)
Be careful with information you find on the internet or social media. In some cases, it can be hard to tell what is true and what is false. This is especially dangerous if people share health information that is not based on science or evidence.
For more information on common ingredients in vaccines in the United States, as well as the process for determining vaccine safety and effectiveness, visit the US Food and Drug Administration (FDA) website.
PAYING FOR VACCINES — Vaccines are available for every child in the United States, even for those who do not have health insurance. If a child does not have health insurance and the parents or caregivers are unable to pay for vaccines, a program called Vaccines for Children is available. This program helps to cover the costs of vaccines given at private doctor's offices, clinics, hospitals, community health clinics, and in some schools.
VACCINE SIDE EFFECTS — Most vaccines are safe and cause few if any serious side effects. Very rarely, serious side effects do occur. Children who develop unusual reactions such as rashes involving much of the body surface, difficulty breathing, excessively high fevers, seizures, or loss of consciousness within a short time after receiving a vaccine should be evaluated by a health care provider.
To report an unusual reaction after a vaccine, you can contact the national Vaccine Adverse Event Reporting System (VAERS, telephone number 1-800-822-7967). Parents who are concerned about a particular vaccine should discuss their concerns with their child's health care provider.
Mild side effects — Vaccines can occasionally cause mild side effects, including:
●A low-grade fever
●A red and tender area at the site of an injection
These side effects do not mean that your child is sick or that the vaccine has given them an infection; rather, they indicate that the immune system is responding to the vaccine.
Depending on how old your child is, there are different things you can do to minimize pain related to vaccine injections (table 1).
Moderate side effects — Only occasionally do children develop a combination of fever, skin rash, swollen lymph nodes, and/or joint pain after vaccination. These reactions, called "serum sickness-like" reactions, may become uncomfortable, though they are rarely, if ever, dangerous, and resolve without treatment in days to weeks.
Severe side effects — Severe side effects of vaccines are rare but may include a severe neurologic reaction (eg, seizures) or severe allergic reactions (eg, anaphylaxis). Allergic reactions usually occur within minutes to hours of receiving the vaccine. If this occurs in the doctor's or nurse's office, emergency care can be given immediately. If your child has a severe reaction later, call emergency medical services (in the United States and Canada, call 9-1-1). (See 'Allergies' below.)
CONTRAINDICATIONS TO VACCINATION — There are some cases in which a child should not receive a specific vaccine or formulation of vaccine.
Allergies — In some cases, a particular vaccine may not be recommended for children with a serious allergy to the following:
●Eggs or egg protein (specifically, people with a known egg allergy should not get the yellow fever vaccine)
●Other vaccine ingredients or components
In some cases, parents may not know their child is allergic to one of these components until the vaccine is given and the child develops a reaction.
Contraindications to live vaccines — Live virus vaccines (eg, the measles, mumps, and rubella [MMR] vaccine) are generally not recommended for children with a weakened immune system since there is an increased risk of infection as a result of the vaccine. However, there may be exceptions to this recommendation.
Administration of the MMR and varicella vaccines should be delayed in children who have recently received a blood transfusion or blood products (eg, immunoglobulin preparations) since these products can make the vaccine less effective.
Conditions that do not affect vaccination — The following conditions do not require delaying or avoiding vaccines:
●Current or recent mild illness
●Current or recent antibiotic therapy
●Previous mild to moderate tenderness, redness, or swelling at the site of injection or fever less than 104.9°F (40.5°C) after a previous vaccination
●A personal history of allergies, except those listed above
●A family history of adverse reactions to vaccines
RECOMMENDED IMMUNIZATIONS FOR CHILDREN — To prevent the diseases for which vaccine protection is available, children should begin receiving vaccines within the first few months of life. This allows the child to be protected from common childhood illnesses as well as illnesses that can develop during adulthood.
Many diseases prevented by vaccines are more serious in young children. Infants and children frequently seen by their health care provider during the first year of life are more likely to receive all of the recommended vaccines. In most states, specific vaccines are required before the child can attend school. This policy is designed to not only protect the individual child but to prevent the spread of certain contagious diseases to other children attending the school. Vaccine requirements tend to vary from state to state.
In the United States, certain vaccines are recommended for children between birth and six years of age. The recommended schedule is available through the Centers for Disease Control and Prevention (CDC). Using combination vaccines can help to reduce the number of shots needed at each visit. (See "Patient education: Vaccines for infants and children age 0 to 6 years (Beyond the Basics)".)
Recommendations for children ages 7 to 18 years are also available. (See "Patient education: Vaccines for children age 7 to 18 years (Beyond the Basics)".)
The CDC provides an assessment tool to determine which vaccines your child needs. The tool may be helpful in reminding parents and caregivers when a child is due for vaccines.
WHERE TO GET MORE INFORMATION — Your child's health care provider is the best source of information for questions and concerns related to your child's medical problem.
This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients and caregivers, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient education: What you should know about vaccines (The Basics)
Patient education: Vaccines for babies and children age 0 to 6 years (The Basics)
Patient education: Vaccines for children age 7 to 18 years (The Basics)
Patient education: Vaccines for travel (The Basics)
Patient education: Mumps (The Basics)
Patient education: Rubella (The Basics)
Patient education: Tetanus (The Basics)
Patient education: Poliomyelitis (The Basics)
Patient education: Measles (The Basics)
Patient education: Tdap vaccine (The Basics)
Patient education: COVID-19 vaccines (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient education: Vaccines for infants and children age 0 to 6 years (Beyond the Basics)
Patient education: Vaccines for children age 7 to 18 years (Beyond the Basics)
Patient education: Vaccines for adults (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Allergic reactions to vaccines
Hepatitis A virus infection: Treatment and prevention
Hepatitis B virus immunization in adults
Meningococcal vaccination in children and adults
Pneumococcal vaccination in children
Vaccination for the prevention of chickenpox (primary varicella infection)
Human papillomavirus vaccination
Seasonal influenza in children: Prevention with vaccines
Standard immunizations for children and adolescents: Overview
Treatment of varicella (chickenpox) infection
Vaccines to prevent smallpox, mpox (monkeypox), and other orthopoxviruses
The following organizations also provide reliable health information.
●National Library of Medicine
●National Institute of Allergy and Infectious Diseases
●Centers for Disease Control and Prevention (CDC) Vaccines and Immunizations
Toll-free: (800) 232-4636
●National Foundation for Infectious Diseases
Tel: (301) 656-0003
●The Children's Hospital of Philadelphia Vaccine Education Center
●Vaccinate Your Family
آیا می خواهید مدیلیب را به صفحه اصلی خود اضافه کنید؟