Can the vaccine Prevnar cause any serious side effects in a 12-month-old? Each time my grandson has been given Prevnar, he has had to go to the emergency room, where they gave him breathing treatments. Both times he was listless, wheezing and having trouble breathing. He was found to be allergic to cats when he was six months old. The doctors have not tested him for any other allergies yet. His eosinophils are 2,500 and his IgE is 800.

Gail

It sounds as if your grandson has some serious allergy problems. Briefly, the most serious type of allergy is called immediate hypersensitivity. In this reaction, the person experiences hives and, possibly, low blood pressure and breathing problems within minutes to an hour after exposure to the allergen (substance that provokes an allergic reaction). This is the type of reaction that, in sensitive individuals, can cause death after a bee sting or a dose of penicillin.

The reaction is complicated, but it involves IgE antibodies, proteins made by the body's immune system that play a key role in allergic reactions. Each IgE molecule reacts only to a specific allergen, such as a protein in bee toxin. When these antibodies bind to the allergen, a series of events follows that ultimately leads to the release of a chemical called histamine. Histamine has many effects on the body, such as constricting the airways and widening the blood vessels.

Prevnar is the new vaccine against Streptococcus pneumoniae (also known as "pneumococcus"). This bacterium is the most common cause of meningitis (inflammation of the membranes covering the brain and spinal cord) in the United States, killing hundreds of children under the age of five each year. It is also the most common cause of otitis media (middle ear infection), which is a relatively mild infection but one that causes a substantial amount of school absences and medical costs to parents. Before Prevnar was developed, the only vaccine available for preventing Streptococcus pneumoniae infection was not effective in young children.

Prevnar is similar to the vaccine used for Hemophilus influenzae (previously the most common cause of childhood meningitis in the United States). It is very effective in preventing disease caused by the seven most common strains of pneumococcus bacteria, and thus markedly decreases the risk of meningitis, pneumonia and even otitis media. It also is a very safe vaccine, causing very few major side effects. About one in three children complain of pain and soreness at the site of inoculation. About one in 10 have mild fever -- as is seen with most, if not all, of the childhood vaccines.

Allergy is the most common serious reaction to the vaccine. Serious allergic reactions and even fatalities have been reported. However, any medication has a potential allergy risk. If your child has an ear infection, for example, he could have a serious allergic reaction to the antibiotic given to treat the infection. In any case, the risk of allergic reaction has to be factored into the cost-benefit analysis of any vaccine. Most experts agree, including those at the Centers for Disease Control and Prevention, that Prevnar's benefits usually outweigh its small risks. The CDC recommends the vaccine for all children under two and for those over two at special risk of the disease.

As far as your grandson is concerned, however, he probably should not receive the vaccine again. The CDC recommends not giving Prevnar to people with immediate hypersensitivity to the vaccine.