Some children with vaccine allergies may still be immunized safely, U.S. pediatricians say.

With close monitoring and a few standard precautions, nearly all children with known or suspected vaccine allergies can be safely immunized, a team of vaccine safety experts in the U.S. argue in the September issue of the journal Pediatrics.

The article gives pediatricians a step-by-step guide on how to quickly identify children who are having an allergic reaction to vaccines.

"We cannot reiterate enough that the vaccines used today are extremely safe, but in a handful of children, certain vaccine ingredients can trigger serious allergic reactions," said Dr. Robert Wood, lead author of the paper and chief of pediatric allergy and immunology at Johns Hopkins Children's Center in Baltimore.

"For the most part, even children with known allergies can be safely vaccinated."

True allergies typically cause immediate reactions involving the whole immune system.

Symptoms of immediate allergic reactions include hives, swelling, wheezing, coughing, low blood pressure, vomiting and diarrhea. They can lead to full-blown anaphylaxis, a life-threatening allergic reaction.

Serious allergic reactions to vaccines are extremely rare and happen in one or two per million vaccinations, according to some estimates.

For children who have already had an allergic reaction to a vaccine or are at high risk of having one, the researchers suggest:

• Going to an allergist for skin prick tests to see whether a child develops antibodies to gelatin used in the diptheria, tetatnus and pertussis vaccine or to egg proteins used in several common vaccines such as the flu shot.
• Using allergen-free brands of vaccines when available.
• Treating a child with anti-allergy medications before giving the vaccine.
• Keeping the child under a doctor's supervision for several hours after the vaccination when allergen-free vaccines are not available.
• Giving blood tests to check a child's immunity levels. If tests show the child has some protective antibodies, then more doses may be temporarily put off.

Communities in the United States and Canada have experienced outbreaks of vaccine-preventable infections such as measles, mumps, rubella and whooping cough in recent years.