A hay fever vaccine that reduces sneezing, itchy eyes and a runny nose by training the immune system to tolerate pollen has been developed by British scientists.
Volunteers who received a jab a week for four weeks in a trial during the hay fever season reported a significant improvement in their symptoms, which they rated each day in electronic diaries.
The trial, conducted in Europe and North America last year, was the world's largest for an allergy vaccine and paves the way for its developers, Allergy Therapeutics in Worthing, to apply for European approval next year.
Attempts to make hay fever vaccines have been beset with difficulties because injecting pollen can trigger serious allergic reactions. To get around this, existing jabs start with tiny doses of pollen, which are gradually stepped up over many years.
"Allergy vaccines tend to be very unfriendly to patients. A typical patient will need to have weekly shots for six months and then fortnightly or monthly shots for another three years before they build up immunity to pollen," said Keith Carter, chief executive of Allergy Therapeutics.
Scientists at the company found they could overcome the problem by modifying pollen contained in their vaccine. Each shot carries extracts from 13 different grass pollens, but they are chemically treated to make them less likely to overstimulate the immune system. The pollen is then combined with a natural amino acid called tyrosin, which makes it release slowly into the bloodstream. A fatty molecule called MPL is added to boost the immune system's response to the vaccine.
In the trial, 1,028 volunteers given the Pollinex Quattro vaccine were asked to score the severity of eight hay fever symptoms, from itchy and streaming eyes to sneezing and a runny nose. They were allowed to take over-the-counter hay fever treatments, such as antihistamines, but had to record whenever they did so.
On average, the participants' symptoms improved by 13% compared with use of a placebo, but a few hundred people who kept the most complete records reported an improvement of 27%. Carter believes the discrepancy is down to conservative assumptions that have to be made about the symptoms of patients whose diaries were incomplete. "I think that they all may have benefited more than the 13% figure suggests," he said.
Hay fever affects around 15 million people in Britain, but that number is rising for reasons scientists do not fully understand. The early arrival of spring and milder autumn weather have stretched the hay fever season, which now runs from March to early August. Grass pollen accounts for about 95% of cases.
The results of the latest trial, previewed in New Scientist magazine, are due to be announced at the European Academy of Allergology and Clinical Immunology conference in Barcelona on Sunday.
Neil Kao, an immunologist at the Allergic Disease and Asthma Centre in Greenville, South Carolina, said the ease of administering the vaccine was a crucial benefit.
