Vaccines 101: What Are Vaccinations?

Childhood vaccinations have curbed the spread of highly contagious, life-threatening diseases for centuries, yet questions about their safety and necessity persist. Here's what you need to know.
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What's the difference between vaccinations and immunizations?

Although these words are often used interchangeably, they mean different things. Vaccinations describe the process of giving vaccines (in the forms of injections, oral drugs, or nasal sprays) to stimulate the production of antibodies to ward off certain diseases. Immunization is the term for making someone immune to a disease; vaccination is a form of active immunization. "When we vaccinate children, it stimulates their immune system to make antibodies that protect them against the bacteria or virus targeted by the vaccine," says Kristen Feemster, M.D., an infectious - disease specialist at The Children's Hospital of Philadelphia. You can also make someone immune by giving him pre-formed antibodies, which is called passive immunization.

Why are vaccinations necessary?

Thanks to vaccines, many infectious diseases that once routinely killed or permanently injured Americans are at all-time lows. Unfortunately, the same can't be said for other countries where diseases like measles, diphtheria, and polio continue to claim thousands of lives every year. "International travel -- both to and from the U.S. -- increases everyone's exposure risk," says Anita Chandra-Puri, M.D., a spokesperson for the American Academy of Pediatrics and a pediatrician at Northwestern Memorial Physicians Group in Chicago.

Do I have to vaccinate my child?

There's no federal mandate; however, each state has its own law that requires children to have certain vaccinations before attending public school. Children whose immune systems are compromised because of organ transplants, cancer, HIV, or other illnesses are medically exempt from certain vaccinations. Some states allow parents to opt out of vaccinations for religious or philosophical reasons. You can find your state's vaccination requirements at


Which vaccines do kids need and why are they necessary?

Are vaccinations safe?

The U.S. has the safest, most effective vaccinations in the world, thanks to stringent testing requirements implemented by the Food and Drug Administration (FDA). Even after a vaccine is approved, the FDA still monitors it for problems. Like any medication, vaccines can cause side effects. Most are mild: soreness or swelling at the injection site, a slight rash, or a mild 24-hour fever. A small number of children experience chills, high fever, and muscle ache. Severe reactions, such as seizures and brain damage, are extremely rare.

Are infants getting too many shots too soon?

Infants' immature immune systems make them especially vulnerable to deadly diseases, so vaccinating early is critical. Exposing babies to a handful of different immunologic components (parts of a bacteria or virus that stimulate an immune response) in the form of a vaccine is nothing compared to the thousands of germs they encounter every day. "An infant's immune system is revved up from the moment he leaves the sterile womb," Dr. Feemster says. In fact, research suggests that babies can theoretically make antibodies to 100,000 vaccines at one time.

Do vaccinations cause autism?

No study has ever shown a connection between vaccines and autism. In 1998, the medical journal The Lancet published a study by British researcher Andrew Wakefield, M.D., conducted on eight children with autism. The study suggested a link between the measles-mumps-rubella (MMR) vaccine, intestinal problems, and, consequently, autism. The study was retracted in 2010 after studies conducted on hundreds of thousands of children failed to replicate his findings. In fact, these studies showed both vaccinated and unvaccinated children were equally at risk for autism. What's more, Dr. Wakefield lost his medical license after it was determined that he acted unethically when selecting study participants, used seriously flawed lab techniques, and fraudulently omitted key facts from his findings. In addition, studies have found no link between autism and thimerosal, a mercury-based preservative once used in vaccines. All vaccines marketed in the U.S. and recommended for children 6 years or younger contain no thimerosal or only trace amounts (1 microgram or less per dose), with the exception of inactivated influenza vaccine. Concerned parents can ask for thimerosal-free flu shots or the nasal spray, which is available to kids age 2 and older.

What diseases are making a comeback?

Any disease can make a comeback if people stop getting vaccinated. There were more than 27,000 incidents of whooping cough (pertussis) in the U.S. in 2010. Studies show that children who skip the pertussis vaccine are 23 times more likely to get sick with the disease than those who are vaccinated, and outbreaks are especially common in schools and day cares. Measles is another reemerging disease. More than 200 unvaccinated American children and adults became ill with measles in 2011 after being exposed to it by infected international travelers. Some parents who forego the varicella vaccine also expose their children to chickenpox, which causes itchy blisters (pox), fever, and fatigue. It also can lead to severe skin infection, scars, pneumonia, brain damage, and death.

What vaccinations does my family need? Which vaccinations are the most necessary?

Every year, Centers for Disease Control and Prevention (CDC) releases updated vaccination recommendations for infants, children, teens, and adults. Here's a look at who needs to get what and when, as of February 2012.

Birth to 6 Years

  • Hep B (Hepatitis B): Given at birth and at months 1, 2, 6, 12, 15, and 18 (7 total doses)
  • Rotavirus (RV): Given at months 2, 4, and 6 (3 total doses)
  • Diptheria (DTaP): Given at months 2, 4, 6, 15, and 18, and between years 4 and 6 (6 total doses)
  • Hib (Haemophilus influenzae type B): Given at months 2, 4, and 6, and between months 12 and 15 (4 total doses)
  • Pneumococcal (PCV; pneumococcus/pneumonia): Given at months 2, 4, and 6, and between months 12 and 15 (4 total doses)
  • Polio (IPV): Given at months 2 and 4; between months 6 and 18; and between years 4 and 6 (4 total doses)
  • Flu (influenza): Given yearly starting at 6 months
  • Measles, Mumps, Rubella (MMR): Given between months 12 and 15, and between years 4 and 6 (2 total doses)
  • Chickenpox (varicella): Given between months 12 and 15 and between years 4 and 6 (2 total doses)
  • Hep A (Hepatitis A): Given between months 12 and 23 (2 total doses)

Ages 7 to 18

  • Tetanus, Diptheria, Pertussis (Tdap): Given at years 11 or 12 (one dose)
  • Human Papillomavirus (HPV): Given between years 11 and 12 (3 total doses)
  • Meningococcal (MCV4; meningitis): Given at years 11 or 12 (one dose); booster at 16 years old
  • Influenza: Given yearly


  • Influenza: Given yearly
  • Tetanus, Diphtheria, Pertussis (Td/Tdap): Booster shot given every 10 years
  • Varicella (chickenpox): 2 doses given during adulthood
  • Human Papillomavirus (HPV): Given to females between years 19 and 26 (3 doses), and to males between years 19 and 21, if not already vaccinated (3 total doses)
  • Measles, Mumps, Rubella (MMR): Up to two doses given by age 50
  • Zoster (shingles): Given at age 60 to 65 and up (one dose)
  • Pneumococcal (polysaccharide): Given at age 65 and up
  • Related: The 6 Vaccines All Adults Need

What vaccines do kids need when traveling?

Vaccinations are not always available in other parts of the world. As a result, life-threatening diseases are still widespread, especially in developing countries. Depending on your destination, your child may need these additional vaccinations:

Meningococcal (MCV4): For children age 2 and older traveling to sub-Saharan Africa, Saudi Arabia, or countries where meningitis is common.

Yellow Fever: For children 9 months and older traveling to Africa, South America, or other countries where yellow fever is common.

Typhoid: For children age 2 and older traveling to Africa, Asia, Latin America, or other countries where typhoid is common.

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