Even though the viral vectors don’t cause illness, they can trigger an immune response in some children. An immune response is the body’s way of learning to fight germs, but it can make your child feel unwell. 

Symptoms of an immune response can include:

• tiredness
• fever
• swollen glands
• pain
• swelling
• needing to urinate or do a wee far less than usual.

Your child's doctor will regularly test their blood and liver to make sure the immune response is in a safe range. Medication doses may change based on the test results.

Children who have more severe symptoms may need medical treatment. Speak to your child’s doctor if you are concerned.

Steroids are medications that reduce inflammation or swelling in the body. Long-term steroid use can affect how your child’s body makes a hormone called cortisol. 

Cortisol is made by the adrenal glands on top of the kidneys. It helps control inflammation, stress, and blood sugar levels.

When steroids are used for a long time, your child’s body may stop making enough cortisol on its own. This can lead to a condition called adrenal suppression. 

Children with adrenal suppression are at risk of developing a life-threatening condition called adrenal crisis when their cortisol levels drop suddenly. This can happen due to:

• sickness
• injury
• stopping medication suddenly
• vomiting medication up before it can be absorbed. 

Symptoms of an adrenal crisis can include:

• extreme weakness
• very low blood pressure
• belly pain
• confusion and dizziness
• nausea and vomiting
• refusal to eat.

Your child’s treatment team will give you an emergency plan to manage adrenal suppression and adrenal crisis.

Call Triple Zero (000) for an ambulance or go to your nearest emergency department if your child shows signs of an adrenal crisis.

Thrombocytopenia is a condition that happens when an immune response destroys platelets in the blood. Platelets help blood to clot, which stops bleeding.

Symptoms of thrombocytopenia can include:

• bleeding for longer than usual after a minor cut or scratch
• bruising easily
• nose bleeds
• bleeding gums.

Your child’s doctor will do regular blood tests after gene therapy to make sure their platelet levels go back to normal.

After gene therapy, traces of the virus used in treatment may leave your child’s body through fluids like:

• snot or mucous
• tears
• spit or saliva
• poo
• urine.

Viral shedding can last for up to a month after gene therapy. 

You can manage viral shedding by:

• wearing gloves when cleaning body fluids like vomit or dirty nappies
• washing hands before and after touching body fluids
• throwing away all nappies, cloths, and paper towels used to clean up body fluids in two tightly tied plastic bags
• washing sheets and clothing straight away on the longest, hottest washing cycle.

Gene therapy is a new treatment, so doctors and scientists are still learning about its long-term safety. They want to make sure that gene therapy does not:

• change DNA in ways that could cause future health issues
• reactivate viruses that are usually harmless but might cause problems after therapy.

After gene therapy, children will need regular check-ups to monitor their health as they grow.

Creating gene therapy is complex and expensive. Scientists must understand the condition and create a specific treatment for each patient.

If a child has an immune response after gene therapy, their body will make antibodies. Antibodies are proteins that help fight viruses and bacteria. This may prevent a child from being able to have more gene therapy in the future as their body will try to fight the treatment.

Scientists and doctors are working to make gene therapy safer and more effective. They are researching new ways to:

• deliver genes into the body
• limit an immune response
• reduce the side effects of treatment.

Gene therapy could be used to treat and even cure many more conditions in the future. The goal is to make these treatments safe, so more children and families can benefit.