Immunizations - Introduction

There is some concern that increasing use of combinations may reduce the potency of some of the vaccines within other combinations. Some parents are also worried about increased side effects. Studies, to date, however, are reporting that combinations are effective and safe.

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Passive Immunity. Another form of protection against disease is called passive immunity. This approach uses immune globulin, which are blood products containing antibodies. Immune globulin is generally used for people who cannot be vaccinated, when immediate protection is required, or to prevent severe complications of the disease. In some circumstances, passive immunity can interfere with active vaccinations, particularly live-virus vaccines, so, if possible, they should not be administered within weeks or even months of each other.

General Information on Side Effects. Vaccines can have side effects, such as swelling at the injection site or fever, which are nearly always mild. There have been a number of reports in the popular press about alarming side effects in many vaccines. Anti-vaccine groups vocally oppose immunizations in children. It is true that no vaccine is 100% safe. However, childhood infections have not been wiped out. Without immunization,children risk diseases that have in the past killed millions of small children.

Special Note on Thimerosal

Thimerosal is a preservative used in many vaccines. It has been in use since the 1930s. The preservative contains small amounts of mercury. Some people are concerned about possible neurologic consequences from cumulative doses in vaccines given to infants. A 2003 study did report an association between thimerosal in DTaP vaccines and a higher risk for problems in neurologic development, including autism and speech problems. However, additional studies are needed to determine any harm from thimerosal other than a delayed allergic response in some children.

In any case, manufacturers have been removing this preservative from vaccines. At the time of this report, all routinely recommended childhood vaccines contain either no thimerosal or only trace amounts. (A trace amount means that a given dose of vaccine contains less than 1 part per million.)

Vaccination Recommendations During Pregnancy

Inactivated-virus and toxoid vaccines are usually safe in pregnant women, although any vaccination should be delayed, if possible, until the second or third trimester. Because of a possible risk to the fetus, live-virus vaccines should not be given to pregnant women or those likely to become pregnant within 28 days unless such women need immediate protection against life-threatening diseases, such as yellow fever, that are only prevented using live-virus vaccines. The live-virus MMR combination, which vaccinates against measles, mumps, and rubella, is not given to pregnant women because of the theoretical risk of the live-rubella vaccine on the fetus.