Children typically are given a number of vaccines according to a standard schedule (see Newborns and Infants: Vaccinating Infants and Children). If vaccines are missed, most can be given later, according to a catch-up schedule. Adults may also be advised to receive certain vaccines. When advising adults about vaccination, a doctor considers the person's age, health history, childhood vaccinations, occupation, geographic location, travel plans, and other factors.
Because vaccines are widely used in the United States, many diseases, once common, are now rare or well controlled.
More than one vaccine may be given at a time. They may be given in one combination vaccine or in individual injections at different injection sites.
Vaccines usually cause no problems, although mild side effects, such as soreness or redness at the injection site, may occur. There has been concern about the safety of thimerosal (a mercury-based preservative in some vaccines) in infants, but there is no evidence of harm. In particular, there is no convincing evidence that vaccines containing thimerosal are related to the development of autism. Nevertheless, most manufacturers have developed thimerosal-free vaccines for use in infants. Information about vaccines that currently contain low levels of mercury or thimerosal is available at the Institute for Vaccine Safety web site.
The only reason for not being vaccinated is a serious allergic reaction (such as an anaphylactic reaction) to the vaccine or to one of its components. However, some vaccines, usually ones that contain live virus, should not be used or should be delayed in people with certain conditions:
The diphtheria, tetanus, and pertussis vaccine is a combination vaccine that protects against these three diseases:
The vaccine has two forms: DTaP for children under 7 years and Tdap for adolescents and adults. Tdap has lower doses of diphtheria and pertussis vaccine, indicated by the lower case d and p.
The vaccine is given as an injection into a muscle. Five injections are given: typically at age 2 months, 4 months, 6 months, 15 to 18 months, and 4 to 6 years. Because pertussis is becoming more common among adults, a booster is recommended at age 11 to 12 years to be followed by a tetanus-diphtheria booster every 10 years. Adults who missed the series of vaccinations given during childhood should get it as adults.
The injection site may become sore, swollen, and red. Serious side effects are rare. They include high fever, inconsolable crying, seizures, and a severe allergic reaction. Serious side effects usually result from the pertussis part of the vaccine. If they occur, the pertussis vaccine is not used again. A vaccine against diphtheria and tetanus may be used instead to complete the vaccination series. The vaccine is not repeated if seizures occur 3 to 7 days after the vaccine is given.
Haemophilus influenzae Type b
The Haemophilus influenzae type b (Hib) vaccine helps protect against bacterial infections due to Hib, such as pneumonia and meningitis. These infections may be serious in children. Use of the vaccine has decreased the incidence of serious infections in children by 99%. These infections are uncommon in adults.
Different formulations of the vaccine are available.
The vaccine is given as an injection into a muscle. Doses are given at age 2 months and 4 months or at age 2 months, 4 months, and 6 months, depending on which formulation is used. In either case, a final dose is given at age 12 to 15 months (for a total of three or four doses). All children should be vaccinated. Adults at increased risk of these infections (such as those with a weakened immune system) may benefit from this vaccination.
Occasionally, the injection site becomes sore, swollen, and red.
The hepatitis A vaccine helps protect against hepatitis A. Typically, hepatitis A is less serious than hepatitis B. Hepatitis A often causes no symptoms, although it can cause fever, nausea, vomiting, and jaundice. Hepatitis A does not lead to chronic hepatitis. Use of the vaccine has reduced the number of people who become infected.
The hepatitis A vaccine is given as an injection into a muscle. Two doses are given to all children: typically at age 12 to 18 months and 6 to 12 months later. It is also recommended for adults at increased risk of the infection.
Sometimes the injection site is sore. No serious side effects have been reported.
The hepatitis B vaccine helps protect against hepatitis B. Generally, hepatitis B is more serious than hepatitis A and is occasionally fatal. Symptoms can be mild or severe. They include decreased appetite, nausea, and fatigue. In 5 to 10% of people, hepatitis B becomes chronic.
The vaccine is typically given in a series of three injections into a muscle. However, if people who have been vaccinated are exposed to the virus, a doctor measures their antibody levels against hepatitis B. If the antibody levels are low, they may need another injection of hepatitis B vaccine.
Vaccination is recommended for all children and adults, especially for adults at high risk of exposure to the hepatitis B virus.
Occasionally, the injection site becomes sore, and a mild fever develops. People with a history of severe allergic reaction to baker's yeast, which is used in the production of the vaccine, should not be given the vaccine.
The herpes zoster vaccine helps reduce the risk of shingles (herpes zoster) and the residual pain it can cause (postherpetic neuralgia). The herpes zoster virus is the same virus that causes chickenpox. After chickenpox resolves, the virus remains in the body. It can be reactivated years later and cause shingles, which is a painful rash, usually on only one part of the body. The rash resolves after several weeks, but postherpetic neuralgia can last for months or years.
The vaccine is similar to the varicella vaccine and contains live virus.
The vaccine is given in one dose as an injection under the skin. It can be given to people over 60.
Rarely, the injection site becomes sore.
The human papillomavirus (HPV) vaccine helps protect against cervical cancer and genital warts, which are caused by the human papillomavirus.
The vaccine is given as an injection into a muscle in three doses: initially, then at 2 and 6 months after the first dose. It is recommended for girls aged 11 to 13 years but can be given up to age 26.
The injection site sometimes becomes sore, swollen, and red. No serious side effects have been reported.
The influenza virus vaccine helps protect against influenza. There are two types of influenza virus, type A and type B, and many different strains within each type. The strains of virus that cause influenza outbreaks change each year. Thus, a new vaccine is needed each year.
Influenza can be mild, causing fever, aches, and fatigue, but it can be serious, sometimes causing death—usually in children under age 1 year or in people over 65.
The vaccine is given as a single injection into the muscle. The vaccine is recommended for children aged 6 to 59 months, people over 50, and others who are at increased risk. Also, the vaccine is usually given to anyone who requests it.
Influenza vaccine is available as an injection or a nasal spray. The nasal spray, which contains live virus, is recommended only for healthy people who are aged 2 to 49 and not pregnant.
Influenza epidemics usually begin in late December or midwinter. Therefore, the best time to get the vaccine is in September or October. A vaccine against avian influenza has been developed in case the virus becomes able to spread from person to person.
Occasionally, the injection site becomes sore. Very rarely, the vaccine causes Guillain-Barré syndrome, a progressive nerve disorder. The nasal spray sometimes causes a runny nose and sore throat. People who have a severe allergy to eggs may have a severe allergic reaction to the vaccine because the vaccine is made from viruses grown in eggs.
Measles, Mumps, and Rubella
The measles, mumps, and rubella (MMR) vaccine is a combination vaccine that helps protect against these three viral infections:
The vaccine is given as an injection under the skin. Two doses are given: at age 12 to 15 months and typically at age 4 to 6 years. If people born after 1956 have never had any one of these infections and have not received two doses of the vaccine, they should be given at least one dose of the vaccine. Adults who are likely to be exposed to these diseases (such as those beginning college, joining the military, working in schools or child care centers, or traveling internationally) should get a second dose of the vaccine.
Pregnant women and people who are have had serious allergic reactions to gelatin or to the antibiotic neomycin should not be vaccinated.
There are individual vaccines for measles, mumps, or rubella. However, a combination vaccine that helps protect against all three is usually used. The combination vaccine is recommended because anyone who needs protection against one of these infections usually also needs protection against the other two.
Some people have mild side effects, such as a fever, a general feeling of illness (malaise), and a rash. Joints may become temporarily stiff and painful, usually in teenage girls and women.
The meningococcal vaccine protects against infections caused by the bacteria, Neisseria meningitidis, which can lead to meningitis or death. These bacteria are the leading cause of bacterial meningitis in children and the second leading cause of bacterial meningitis in adults. The infection can cause the following symptoms:
The vaccine is given in one dose as an injection under the skin or into a muscle. Two formulations are available in the United States: the polysaccharide vaccine for children aged 2 to 10 years and the conjugate vaccine for people aged 11 years or older.
The meningococcal vaccine is recommended for all children at age 11 to 12 years. It is also recommended for the following:
The injection site may become sore, swollen, and red. A few people have a mild fever and fatigue. Guillain-Barré syndrome developed in a few people after they were vaccinated with the conjugate vaccine. Thus, this vaccine should not be given to people who have had this syndrome.
Pneumococcal vaccines help protect against bacterial infections caused by Streptococcus pneumoniae, such as ear infections, sinusitis, pneumonia, and meningitis.
Two formulations of the pneumococcal vaccine are available. The conjugate vaccine is given typically at age 2 months, 4 months, 6 months, and 12 to 15 months. The polysaccharide vaccine is given to older children at high risk of developing pneumonia or another pneumococcal infection in two doses: at age 24 months and 3 to 5 years later. The polysaccharide vaccine is also recommended for older children and adults who are at high risk of developing these infections.
The polysaccharide vaccine is effective in about two of three adults, although it is less effective in debilitated older people. It is more effective in preventing some of the serious complications of pneumococcal pneumonia than in preventing the pneumonia itself. Although one injection of the vaccine may provide lifetime protection, people at high risk are advised to be vaccinated again after 5 years.
Occasionally, the injection site becomes painful and red. Other side effects include fever, irritability, drowsiness, loss of appetite, and vomiting.
The polio vaccine protects against polio, a very contagious viral infection that affects the nerves. Polio can cause permanent muscle weakness, paralysis, and sometimes death.
Two formulations are available. One contains killed virus and is injected. The other contains live, weakened virus and is taken by mouth. The live-virus vaccine is no longer available in the United States because it causes polio in about 1 of every 2.4 million people who receive the vaccine.
The vaccine is given in four doses: at age 2 months, 4 months, 6 to 18 months, and 4 to 6 years. Because polio is now so rare in the United States, unvaccinated people over 18 years are not given the vaccine unless they are traveling to an area where polio is common.
People who have allergies to the antibiotics streptomycin, neomycin, or polymyxin B may have an allergic reaction to the vaccine. The vaccine may contain small amounts of these antibiotics.
The rotavirus vaccine helps protect against gastroenteritis, which causes vomiting, diarrhea, and, if symptoms persist, dehydration.
This vaccine is part of the recommended vaccination schedule for children. Three doses are given: at age 2 months, 4 months, and 6 months.
No severe side effects have been reported, but mild, temporary diarrhea occurs in 1 to 3% of children within 7 days of receiving the vaccine.
The tetanus vaccine protects against the toxin produced by the tetanus bacteria, not the bacteria itself. Typically, the bacteria enter the body through a wound and begin to grow and produce the toxin. The toxin causes severe muscle spasms and can be fatal. Therefore, vaccination is particularly important.
The vaccine is typically given during childhood, as part of the diphtheria, tetanus, and pertussis vaccine (see Immunization: Diphtheria-Tetanus-Pertussis). The combination vaccine is given in five injections, followed by a booster that contains the same amount of tetanus vaccine but a smaller amount of diphtheria and pertussis vaccine. The booster is given at age 11 to 12 years. Because immunity against pertussis is decreasing, people aged 16 to 64 should receive this booster if they have not received it previously. A booster of the tetanus vaccine is recommended every 10 years thereafter. Also, people sometimes need to be vaccinated after an injury.
Sometimes the injection site is sore, swollen, and red. Serious side effects are rare and include severe allergic reactions.
The varicella vaccine helps protect against chickenpox (varicella), a very contagious infection caused by the varicella-zoster virus. It causes an itchy rash that looks like small blisters with a red base. In some people, the brain, lungs, heart, and joints become infected. The virus remains in the body. If it is reactivated, it can cause shingles years later.
Vaccination against varicella is part of the routine vaccination schedule recommended for children. The vaccine is given as an injection under the skin. Two doses are given: at age 12 to 15 months and at age 4 to 6 years. It is also recommended for all adolescents and adults who have not had the vaccine or the disease. It is given to them in two doses 4 to 8 weeks apart.
Because the vaccine contains live virus, it is not given to pregnant women, people with a weakened immune system, or people with cancer of the bone marrow or lymphatic system.
The vaccine is safe, and side effects are mild. In fewer than one fourth of the people who get the vaccine, the injection site becomes painful, swollen, and red. Very occasionally, a chickenpox-like rash develops.
Taking aspirin and related drugs (salicylates) after vaccination can cause Reye's syndrome in children under 16 years old. Thus, such children should not be given these drugs for 6 weeks after vaccination.
Last full review/revision July 2008 by Fred H. Rubin, MD