Now is a great time to make sure your children's immunizations are up-to-date.

The state of Iowa requires children to be immunized at certain ages and intervals in order to enroll in school. Families have to document that children have been immunized against various diseases and children also need to receive periodic booster shots.

In Iowa, children enrolling in school must be vaccinated against diphtheria, tetanus, and pertussis; hepatitis B; measles and rubella; polio; and varicella (chickenpox). A slightly different set of requirements applies to children entering licensed childcare facilities. Complete information can be found online at the Iowa Department of Public Health web site, www.idph.state.ia.us, and you may also contact your local school district or county public health department.

Children about to enter kindergarten can receive their required immunizations any time after their fourth birthday and prior to entering school.

Vaccines prompt the body to produce antibodies, which block the development of infection. Some vaccines produce enough antibodies in only one dose. Others require additional doses (or boosters) to build up enough antibodies for protection.

Iowa requires an additional measles booster before a child enters kindergarten. Older students and even adults should also receive boosters because previous doses may not provide sufficient protection. Boosters remind the body how to make antibodies and protect itself.

Families should also discuss what recommendations their health care provider has regarding influenza immunizations, or flu shots, for children.

It is a good idea to keep copies of your children's immunization records, which can help save them from having to get additional shots because of a lack of certainty about which vaccines they have received and when they received them.

Adverse reactions to immunizations are rare and the risk of complications is far less than the risk to a child and the community from not being immunized. In fact, the more people in a community who are immunized against a disease, the less likely it is that an outbreak would occur. Public health specialists call this concept "herd immunity."

Thanks to immunizations, diseases such as polio, mumps and diphtheria are almost unheard of today. But health care professionals say being immunized against potentially dangerous childhood diseases should still be a top priority for families.

Without proper immunization, the number of cases of dangerous diseases can dramatically increase, as we saw with a recent resurgence of measles. In 1983, there was an all-time low of only 1,500 reported measles cases in the United States. About 28,000 cases were reported in 1990, including 60 deaths, most of whom were young children who had not been immunized.