Research by the Instituto de Saúde Pública da Universidade do Porto (ISPUP) has concluded that immunotherapy, also known as anti-allergic vaccine, or allergy shot, can help prevent the progression of allergic diseases and the development of asthma in children with sensitivity to allergens such as pollen and dust mites.
This therapy acts by administering controlled doses of allergen extracts, with the aim of retraining the immune system towards tolerance, thus responding less and less to potential allergens.
Instead of just controlling and relieving symptoms, as is the case with antihistamines and nasal corticosteroids, which are the most widely used treatments, allergy shots seek to fight the cause of allergies, reducing symptoms in the long term.
To ensure its effectiveness, immunotherapy generally lasts from 3 to 5 years, with continuous administration of the vaccine subcutaneously or orally, and must be prescribed by a doctor specialised in immunoallergology.
To find out if immunotherapy would be effective in preventing the development of asthma in individuals with sensitivity to aeroallergens – airborne allergens such as pollen and dust mites – the researchers performed a meta-analysis of 18 previously published studies, summing up a total population of 325,826 people evaluated.
“What’s new here is the range of studies we evaluated, because we included not only clinical trials, conducted in a controlled environment, but we also used data from real-life studies. Therefore, we ended up combining several sources of information in a single study and reached the conclusion that the preventive effect of immunotherapy in the progression of allergic disease and in the development of asthma is very likely”, says Mariana Farraia, first author of the study and researcher at the Laboratory of Epidemiology of Allergic Conditions, part of the Associated Laboratory for Translational and Integrative Population Research (ITR), coordinated by ISPUP.
When compiling the data from the studies covered by the meta-analysis, the researchers found that, after immunotherapy against grass pollen and dust mite allergy, there was a 25% decrease in the risk of developing asthma.
Although the studies analysed included both children and adults, the effects of immunotherapy on asthma prevention were particularly demonstrated in children. Moreover, the effect was shown to be greater when the treatment lasted for at least 3 years, and when patients had sensitivity to only one allergen.
The researchers involved highlight the pioneering nature of this study, the first to solidify the hypothesis of the existence of a long-term therapeutic solution for allergies and asthma, capable of reversing the natural history of these diseases, which tend to progressively worsen over time.
“There was a perception that allergy shots could modify the natural history of the disease, and this is a topic that has been debated for quite some time, with pros and cons involved. What this study shows, for the first time, is that it is possible to change the natural history of the disease with this intervention, which is completely innovative,” explains André Moreira, coordinator of the study.
The investigation, entitled Allergen immunotherapy for asthma prevention: A systematic review and meta-analysis of randomized and non-randomized controlled studies, was published in the scientific journal Allergy.
The study was also signed by the researchers Inês Paciência (ISPUP), Francisca Castro Mendes (ISPUP), João Cavaleiro Rufo (ISPUP), Mohamed Shamji (National Heart and Lung Institute, Imperial College London) and Ioana Agache (Faculty of Medicine, Transylvania University).
The research is part of Mariana Farraia’s PhD project, which received funding from the Portuguese Foundation for Science and Technology (FCT). Researcher João Rufo, one of the study’s co-authors, also receives funding through the Stimulus for Individual Scientific Employment.