Allergen Immunotherapy in Children

Paediatric allergy specialist, Dr. John Chapman, consultant, paediatric allergy specialist at the James Paget Hospital in Norfolk is an expert in immunotherapy as a treatment solution for people living with allergic disease with  Allergy UK Nurse Advisor Holly Shaw, puts her questions on this treatment option to Dr John Chapman.

Let’s start with an introduction – what is immunotherapy?

Immunotherapy, sometimes called desensitisation, has been around for a long time. It’s been around for so long that I had it when I was a child when you could be desensitised to just about anything that you’re allergic to; pollens, dusts, cats, dogs, and even drugs to a certain extent. More recently immunotherapy is being used to treat food allergies.

Immunotherapy or desensitisation is a way of training your immune system into accepting something that it decided it doesn’t like. Using grass pollen as an example, if you have hay fever, the pollen comes every summer, and your hay fever gets bad, but it goes away in the winter. As the hay fever settles down, so too does your immune system. However, the immune system is surprised once again the following summer when the pollen returns, triggering the whole reaction all over again, sometimes, even year on year.

With desensitisation immunotherapy, the treatment keeps that level of pollen going the whole year.  Patients may even be given a higher dose of pollen. With sublingual immunotherapy for example, every single day, you would put pollen under your tongue or in your mouth so that every day your immune system is seeing pollen. Eventually, your immune system thinks ‘Why am I reacting to this every day? It’s not stopping. I will just down regulate everything, and I’ll stop flapping about it’. It’s similar with subcutaneous immunotherapy, which you have the over the winter. It sits in your body and releases pollen allergens through the winter, so you don’t get that summer and winter change. Eventually your body just thinks this is not a bad thing and your immune system just seems to get used to it.

How is the immunotherapy or desensitisation administered?

There are several different types of immunotherapy, administered in different ways. Some treatments are given via an injection, some are given under the tongue and some are given in oral form. Different patients may be better suited to receiving the treatment in one way versus another. For instance, children don’t like needles and subcutaneous injections are painful. They’re also not easy to access in every part the country, with patients sometimes having to travel distances in hospitals to receive the treatment. In such instances, a much easier way of delivering immunotherapy for grass for example, is via sublingual immunotherapy.  This is where a patient receives a small amount of whatever they happen to be allergic to such as pollens, cats, dogs, dust mites, and you put it in their mouth. A child will still have to get the first dose in hospital but once that first dose is given there’s not usually any up dosing. As the chances of having a reaction after that are almost zero, you can continue with the treatment at home. The difficulty is that a patient has to do it every single day, summer and winter, for at least three years. A commitment has to be there to do it for the whole of this extended period of time. However, it’s a different commitment to having an injection and going somewhere for it. So different ways of administering the treatment work for different people. It is a treatment which offers hope to those families and children, with severe symptoms that aren’t well controlled by pharmacological methods and other interventions.

Is immunotherapy a treatment that is widely received in the UK?

There’s very little immunotherapy undertaken in the UK compared to just about any other country in Europe. And that’s down to funding and how the NHS is set up. On the continent, if a patient is diagnosed with a really bad pollen allergy, they would be started on immunotherapy desensitisation in some form.  Whereas, in the UK, it’s quite unusual to receive immunotherapies. Instead, patients take lots of antihistamines and nasal sprays, and struggle through the summers. I know of incidences where a child has had to wear swimming goggles inside in the summer, because their pollen allergy was so bad they couldn’t think about going outside.  This is a really significant impact from a quality-of-life perspective.

You mention that for immunotherapy treatment to work, it really requires a commitment to the treatment from the patient for it to work.  How do people manage that commitment – do people stay for the full programme or is there a high dropout rate?

It depends on how bad the problem is and the method you choose to receive the immunotherapy. For sublingual immunotherapy, for example, with grass pollen, most people can tolerate the presence of the side effects:  once they get past the itchy mouth that’s typical in the first few weeks, it’s not such a big deal. Provided patients can build this into their lifestyle, they will only be visiting the hospital maybe once a year. The other end of the spectrum is the treatment regime required for oral immunotherapy for peanut allergy for example. This is a big time commitment and requires hospital attendance. To receive the new treatment for peanut allergy, patients still have to go through the same diagnostic process. They need to be diagnosed with a skin prick test and then the patient would need to attend hospital for an up-dosing day. This would start with a tiny, dose of peanut and increase up to a dose equivalent to about 100th of a peanut in the first day. The following day a patient would need to return to start on a dose that will continue (to take in the hospital setting?) for the next two weeks at home.  However, after two weeks, patients need to return to the hospital to receive another dose for two weeks and this continues for the first three or four months; every two weeks you have to attend hospital. If a patient lives close to the hospital, a school is amenable and they’re not in a year of exams, then it may be manageable.  But if the clinic day falls on the day of an important lesson every week – maths for example – then that might be a consideration which affects uptake and adherence. It’s important for children and their families to have all the information about the treatment and the treatment regime in order to make a decision.  Patients may choose to defer the treatment to a time which is more suited to their lifestyle demands so it’s important that the treatment remains there as an option for patients.

Are there any groups of patients for whom immunotherapy is not suitable?

There are some patients where immunotherapy may not be a suitable option. A patient with asthma who wants to have desensitisation, needs to get their asthma under control before treatment. Anyone who wants to do desensitisation needs to commit to take it every day – and we know most people don’t manage to take their medicines every single day.  However, with desensitisation, if a patient forgets to take it for a week for example and they go back to taking it, they could have a reaction. The treatment is meant to make patients safer, but without that commitment to take it every day, it can make patients less safe – they may end up having more reactions than without the treatment. For patients who may struggle with compliance to start with, they probably shouldn’t start with desensitisation because the immunotherapy probably won’t work and may make them have more symptoms.

How soon do patients begin to feel the benefits of immunotherapy?

The length of time it takes patients to see the benefit will vary. If a patient has had pollen desensitisation in the winter beforehand, then by the first summer, its often kicked in so it may the hay fever symptoms may be felt a bit less, and the second year might be a bit less again, and then by the third year, patients may still be seeing an improvement in their symptoms. Most patients will undertake the treatment for three years and occasionally, when people are still improving in the third year, they might do a fourth year but that’s probably less common. It’s not a treatment where there will be an immediate relief, it’s a gradual, deferred improvement.

What are the risks or side effects of immunotherapy?

The different ways to receive immunotherapy have different risks. Subcutaneous immunotherapy can have a risk of anaphylactic reactions, which is why you don’t get it in a GP surgery anymore, you get it in a specialist centre. Anaphylaxis to that is still unusual, but it can happen. Also, people may get painful arms because they’ve had an injection of something to which they’re allergic.

Sublingual immunotherapy has probably got the least side effect profile. Grass pollen and dust mite can be taken by mouth every day.  This is going to make patients itch in the mouth for the first few weeks but that settles down.

Oral desensitisation, such as oral peanut desensitisation may cause an itch in the mouth, and there might also be a bit of tummy ache, or a bit of diarrhoea. These will tend to settle through the time.

Very occasionally, people just can’t take it because the side effects are too bad. It may be that they’re just too sensitive to it or because other kind of lifestyle issues are getting in the way for them as well.

Is there a screening or assessment process to determine eligibility for immunotherapy?

The main screening for immunotherapy is really that there is limited funding for it. Unless patients can get referral to a specialist centre then patients are probably not going to get it. Funding is reserved for exceptional cases, usually the patient who is the worst in the area.

In the case of oral peanut desensitisation because it is brand new and just agreed by NICE in February, it’s too soon for many hospitals to have managed to introduce it and that’s because it hasn’t come with any funding.  Over this 12 month period, we will be looking at which patients may benefit from this treatment.

This aside, first of all, eligibility comes from the patients. They have to want to do it, they have to commit to doing it and know that it’s not a cure. In the case of oral peanut desensitisation for example, they have to be aware that when they’ve been through the treatment it’ll make peanuts safer for them – from cross contamination for example – but we don’t think it means a patient can have a free amount of peanut in their diet.

What is the patient pathway for those patients who do want to seek immunotherapy treatment?

For patients seeking immunotherapy treatment, in the first instance, a patient would need to come through their GP and then through to an allergy specialist to then go on to be referred to an allergy specialist at an allergy centre probably in London or Cambridge – where the treatment can be delivered. Usually, the patients would have to travel to that centre to receive the treatment. In addition to a time commitment from the family, there’s a financial commitment, because depending on where you are in the UK or England, it’s not cheap to London several times a year. It does require a significant commitment from the patient and family