Ambrosia artemisiifolia, also known as common or short ragweed, is an invasive annual flowering herbaceous plant that has its origin in North America. Nowadays, ragweed can be found in many areas worldwide. Ragweed pollen is known for its high potential to cause type I allergic reactions in late summer and autumn and represents a major health problem in America and several countries in Europe. Climate change and urbanization, as well as long distance transport capacity, enhance the spread of ragweed pollen. Therefore ragweed is becoming domestic in non-invaded areas which in turn will increase the sensitization rate. So far 11 ragweed allergens have been described and, according to IgE reactivity, Amb a 1 and Amb a 11 seem to be major allergens. Sensitization rates of the other allergens vary between 10 and 50%. Most of the allergens have already been recombinantly produced, but most of them have not been characterized regarding their allergenic activity, therefore no conclusion on the clinical relevance of all the allergens can be made, which is important and necessary for an accurate diagnosis. Pharmacotherapy is the most common treatment for ragweed pollen allergy but fails to impact on the course of allergy. Allergen-specific immunotherapy (AIT) is the only causative and disease-modifying treatment of allergy with long-lasting effects, but currently it is based on the administration of ragweed pollen extract or Amb a 1 only. In order to improve ragweed pollen AIT, new strategies are required with higher efficacy and safety.

BACKGROUND In pediatric ages, sublingual immunotherapy (SLIT) allows allergic children to approach the inhaling desensitizing therapy. However, SLIT causes quite a few compliance problems and sometimes it is difficult to carry it out for the required long term. The alternative is subcutaneous immunotherapy (SCIT), commonly performed with a syringe. This technique hasn't changed much in time and it is not without risks or discomfort. This has led to the search for alternative ways of vaccine administration, in order to reduce discomfort to children by improving compliance and diminishing the potential risks of adverse reactions. OBJECTIVE The study aimed to assess the patient's perceived pain and the safety of a new way of administration of SCIT, with a needleless device. METHODS Children with grass or mite-induced allergic rhinoconjunctivitis and/ or bronchial asthma were prescribed a glutaraldehyde-polymerized allergenic extract (Allergovac Polymeryzed®, Bial Aristegui, Italy). Each dose was divided in two parts: half injected with the traditional syringe (dose A), half in the other arm with a needleless device (Injex, Greytree, Ross on Wye, UK; dose B). Patients were blindfolded. The perceived pain and the difficulties of the procedure were registered on a dedicated VAS scale immediately (time 1) and 20 minutes after the first injection (time 20). Also, we evaluated the occurrence of occasional adverse events during such procedure and we assessed the perceived difficulty by the doctor administering with such method. RESULTS 39 patients, aged 5-18 years, were recruited and assessed. All patients completed the study, which involved 468 grass pollen AIT SCIT doses, of which 234 with needleless device. At time 1, the use of the needleless device led to an 88% reduction of the pain perception average rate (from 16,8 to 1,97). The difficulty for the technician to make the inoculum was also analyzed (expressed by an increasing rate, from 0 to 4). In all 6 doses, for each child, the difficulty rate 2 relates to an almost constant number of patients, while the highest difficulty rates (grade 3 and grade 4) gradually decrease (until they disappear). CONCLUSIONS The vaccine administration with needleless device has various advantages and it ensures a better acceptance in comparison with administration by traditional SCIT. This is important in order to start the immunotherapy at an early stage, as it is recommended by the most recent studies, so that the natural evolution of the allergic disease can be immediately modified. The new technique ensures a higher safety both for the vaccinator and for the patient, with a better acceptance of the procedure by the patient and therefore a better and wider compliance to the vaccination schedules.

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