Patients receiving the experimental vaccine showed an average 60 per cent reduction in typical allergy symptoms, such as sneezing, runny nose, watering eyes and itching for at least two years, compared with those receiving a placebo.

Researchers at the Johns Hopkins University School of Medicine, in Baltimore, Maryland, believe that a six-injection treatment with the new vaccine, known as AIC, could offer a significant improvement over traditional allergen immunotherapy, which can require several years of weekly or bi-weekly injections.

AIC contains a short piece of DNA known as an “immunostimulatory sequence” that can modify immune system reactions and reduce the typical symptoms of ragweed allergy, more commonly known as hay fever.

The experimental therapy also holds the promise of one day eliminating the need for traditional allergy medicines such as nasal steroids and antihistamines.

The study, published today in The New England Journal of Medicine, was conducted during two hay fever seasons using 25 volunteers, aged 23 to 60, with a demonstrated history of ragweed allergy.

Fourteen people received the vaccine, administered as six weekly injections, while eleven others received placebo injections.

During the test period, allergic symptoms were monitored and recorded, down to how often volunteers’ noses ran and how many times they sneezed.

Relief from allergic symptoms was as pronounced in the second year as in the first, even though no more vaccine was administered.

Hay fever is estimated to affect more than seven million Britons. Like other allergies it is caused by an overreaction of the immune system to an otherwise harmless substance, such as tree and plant pollens.

In allergic individuals, antibodies known as IgE are responsible for mediating the allergic response.

In the current study, the researchers found that, like standard immunotherapy, AIC blocks the seasonal rise in ragweed-specific IgE in people who are allergic.

Investigators at the University of California, in San Diego, had observed previously that a particular sequence of DNA, derived from bacteria, shuts down a T-helper cell (Th2) involved in the body’s inflammatory response.

It is thought that the vaccine lessens the immune system’s excessive reactions to inhaled allergens by stimulating protective cells that turn off the Th2 helper cells.

Together, the researchers believe, these results hint that AIC is successfully reprogramming the immune system to tolerate the presence of allergen, without overreacting.

Peter Creticos, medical director of the Johns Hopkins Asthma and Allergy Centre, said that the vaccine worked by suppressing acute allergic reactions such as sneezing, and by helping the body better regulate the chronic inflammation that causes itchy eyes and a runny nose.

“Long-lasting relief can be achieved with a concise, six-week injection regimen, as opposed to the current, tedious, four to five-year course of treatment with allergen immunotherapy,” Dr Creticos said. “And we’re not just treating the symptoms, we’re targeting the fundamental defects in the immune system that cause allergy.”

Further studies are under way to examine the drug’s lasting effects in a larger group of participants.

“Our hope is that we can one day provide a long-term cure for hay fever and other chronic inflammatory diseases,” Dr Creticos said.

Times Recommends

• Strange burns increase phosphorus concerns
• Smart meters call time on parking cheats
• Four-eyed fish uses mirrors to see in dark