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In easy-to-understand language
Note: The terms "immunization," "vaccination," and "inoculation" are used to mean essentially the same thing throughout this site.
Vaccine safety is taken very seriously. The Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) collaborate in managing, for instance, a multi-component system to monitor and assess the safety of vaccines. This system includes a Vaccine Adverse Event Reporting System (VAERS) that enables parents, health care providers, and others to report what they believe are possible reactions to vaccines, as well as databases and studies that evaluate potential links between vaccines and adverse reactions. This system also includes the development and distribution of educational materials that help parents and health care providers understand vaccine benefits and risks.


  • In 1999, the Advisory Committee on Immunization Practices (ACIP) recommended the use of the inactivated polio virus vaccine (IPV) to eliminate the rare complication of vaccine associated paralytic polio, found with the use of oral polio vaccine.
  • In 1997, due to safety concerns with the whole cell pertussis component of the diptheria tetanus pertussis vaccines (DTP), a recommendation to change to a safer form of the pertussis component (DTaP) has resulted in far fewer adverse events.
Important Facts About Polio and DTaP Vaccines

Polio Vaccine

  • Under the updated schedule, IPV is now the only polio vaccine recommended for routine use in the United States. All children should receive a dose of IPV at 2 months, 4 months, between 6-18 months, and 4-6 years, for a total of 4 doses.
  • Since 1979, the only cases of polio in the United States have been caused by the oral polio virus vaccine. The risk of vaccine-associated paralytic poliomyelitis (VAPP) from the oral polio vaccine is about one case in every 2.4 million doses.
  • Since 1997, after the sequential schedule (with 2 doses of IPV followed by 2 doses of OPV) was recommended, VAPP has decreased in the U. S. No cases of VAPP have been associated with IPV, so the recommendation to use an all-IPV schedule for routine childhood polio vaccination will eliminate the rare occurrence of VAPP in the U. S.
  • Since the sequential schedule has been well accepted despite the need for additional injections, and the global eradication of polio has progressed rapidly making importation of wild_type polio virus into the U.S. much less likely, the switch to an all_IPV schedule is the best policy.

DTaP Vaccine

  • In 1997, the ACIP recommended diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccines to be given for all five doses in the childhood immunization schedule. Prior to 1996, whole-cell pertussis (DTP) vaccines were used exclusively for the first three doses and either DTaP or DTP vaccine could be used for the remaining two doses.
  • The change to recommend DTaP vaccines for all five doses in the schedule was made because of its improved safety over previous vaccines.
  • The DTaP vaccines, which are made with purified components from the pertussis bacterium, are less frequently associated with adverse reactions. Local adverse reactions following the first 3 doses of DTaP were significantly less common than following DTP vaccination. Systemic reactions following DTaP vaccination also occur less frequently than following DTP.
  • In addition to their improved safety profile, DTaP vaccines have been shown to be at least as effective as whole-cell DTP vaccines.
CDC, National Immunization Program:

Last updated: August 2001

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