Vaccine 'hope' to end hay fever misery
“New jab could relieve your hay fever for weeks,” reports the Daily Mail.
The news is based on the results of a small trial that investigated whether injections of low doses of pollen into the skin reduced the allergic reaction to grass pollen in people with hay fever.
Most hay fever treatments relieve symptoms when they occur using medications such as antihistamines.
Currently, the only effective preventative treatment for hay fever is known as immunotherapy, which involves injecting high doses of pollen into a deeper layer of skin. However, due to the high doses involved there is always a risk that the treatment can trigger a serious and wide-ranging allergic reaction (anaphylaxis). Immunotherapy is also both time-consuming and expensive.
In this study much lower doses of pollen were injected into an upper section of the skin (the dermis) to see if the effect was similar to that found with traditional immunotherapy. Researchers found that the low-dose treatment did reduce allergic-type symptoms, such as redness and swelling, at the end of the course.
This is promising research that does provide some ‘proof of concept’ that a new low-dose immunotherapy may be possible at some point in the future.
The authors are now starting a larger clinical trial, the PollenLITE trial to explore the results further.
Where did the story come from?
The study was carried out by researchers from Imperial College London, King’s College London and the Medical Research Council (MRC) and Asthma UK Centre in Allergic Mechanisms of Asthma. It was funded by the Health Foundation and Academy of Medical Sciences and by the Royal Brompton and Harefield Hospitals Charitable Trust.
The study was published in the peer-reviewed Journal of Allergy and Clinical Immunology.
This story was covered by the BBC, The Daily Telegraph and the Daily Mail. Most of the coverage was accurate although the headlines mentioning a “hay fever vaccine” were misleading. The researchers were actually looking at low-dose immunotherapy. Immunotherapy at higher-doses for hay fever is already an available treatment.
The Telegraph’s prediction that a vaccine will be available “in months” seems wildly optimistic.
What kind of research was this?
This was a randomised controlled trial that aimed to investigate whether injections of low doses of pollen into the skin could reduce the allergic reaction to grass pollen. Most injections are given into the subcutaneous tissue (below the skin). In this study injections were made into the dermis, which is the layer of tissue found between the subcutaneous tissue and the upper layer of skin (the epidermis). The researchers were testing whether a lower dose of the grass pollen could be used with the intradermal technique compared with the doses used for subcutaneous injection.
A randomised controlled trial is the ideal study design to answer this question.
This study was small, with only 30 participants and the effect of the injections on common hay fever symptoms such as sneezing and itchy, red watery eyes was not determined. Only allergic-type symptoms affecting the skin were assessed. However, because of the way allergic symptoms are triggered by the immune system it would be unusual for a treatment to prevent some symptoms without affecting others.
What did the research involve?
The researchers recruited 30 people who were allergic to both timothy grass and silver birch pollen. They randomly divided them into three groups, balancing the groups for severity of allergy.
- People in group A received six low-dose injections of grass pollen into their arms at two-week intervals. They also received injections of birch pollen at the start of the study and week 10.
- People in group B received two injections separated by 10 weeks. They also received injections of birch pollen at the start of the study and week 10, the same as those in group A.
- People in group C received a single grass pollen injection at the end of the 10-week study. People in group C also received the birch pollen injection at week 10.
At the end of the study, the researchers measured the early and late immune responses to the injections.
Early responses included the size of weal that formed after the injection. Late responses included redness, swelling, oedema (fluid retention) and thickening of the skin after 24 hours.
The researchers report that the dose of allergen given to group A was 2,000-fold less than that given by deeper subcutaneous injection over the same period in another trial.
What were the basic results?
At the end of the study there was no difference in the early responses to the injections. Participants in all three groups had similar sized weals after injection with either grass or birch pollen.
However, the late responses to grass pollen were significantly reduced in group A, who had received regular injections of grass pollen, compared with those in the control groups B and C.
There was no difference in the late responses to birch pollen, which had only been administered at the beginning of the study to groups A and B, and at the end of the study to all three groups. This showed that regular injections with grass pollen reduced the response specifically to grass pollen, while less frequent injections of birch pollen had no effect on response.
The researchers then looked to see whether the difference in secondary responses occurred only when injections were made into the arm, where the regular injections had been made, or whether the same effect was seen if injections were made into the back. They again found that late responses were reduced in participants in group A compared with those in group C.
How did the researchers interpret the results?
The researchers concluded that low-dose injections of allergens into the dermis suppress late allergic responses. This suppression is specific for the type of allergen and affects the whole body.
Conclusion
This small trial provides evidence that repeated injections of low-doses of allergens into the dermis, which is situated just under the upper layer of skin, can reduce the late immune response to grass pollen. Further clinical trials are required to confirm these results, and to see whether this reduction in late immune responses actually improves symptoms in hay fever sufferers.
The news reports that the authors are now starting a larger clinical trial, the PollenLITE trial.
