The most common side effects of any vaccine are pain, soreness, and fever. Fortunately, those are the most treatable side effects as well. All three symptoms respond well to appropriate doses of acetaminophen (Tylenol) or ibuprofen (Motrin, Advil). In our experience, ibuprofen lasts longer, over six hours, and does a better job of reducing a high fever. However, ibuprofen is known to upset the stomach.
Acetaminophen is easier on the stomach but requires dosing every four hours. Unless a child is vomiting or has stomach pain, we start with ibuprofen. If a child has stomach symptoms, though, we prefer to use acetaminophen. Aspirin is never recommended for children under the age of eight, due to an increased risk of liver complications.
Another reason we prefer ibuprofen over acetaminophen is that a study published in the fall of 2008 linked acetaminophen use to an increased risk for asthma. The study was published in a respected medical journal, The Lancet, and over two hundred thousand children were studied in thirtyone countries. This was a huge study; most medical studies contain fewer than a thousand participants. The results showed that children who received paracetamol (known as acetaminophen in the United States) in the first year of life had a higher risk of developing asthma by the time they were seven years old. In addition, the response was dose dependent, meaning that infants who used paracetamol more frequently had an increased risk of developing asthma when compared with children who received it only occasionally.
We am not using this study to always recommend against acetaminophen. As we said earlier, if a child is vomiting or has stomach pain, we prefer to use acetaminophen. And the risk was not extraordinarily high, only an increase of one and a half times the usual rate for occasional users of acetaminophen and three times the usual rate for frequent users. However, all things being equal, we do recommend ibuprofen over acetaminophen. Both do a good job of relieving pain and reducing fevers, and there was no association between ibuprofen and asthma in the Lancet study.
In our office, we always offer pain medication when we are giving vaccines to children. About half the parents like to give a dose of medicine before the vaccine is given. Their rationale is that they know vaccines usually hurt and don’t want to delay treating the pain. Also, if you give the pain medicine far enough in advance of the injections, you have a better chance of the medicine controlling both the immediate pain of the injection as well as the sore muscle that occurs later on.
The other half of the parents are more concerned about giving unnecessary medicine to their children and prefer to wait to see if any pain relief is needed. For those parents concerned about the medication, we try to reassure them that with appropriate dosing, the medication is very safe in children.