Just six injections of the DNA-based vaccine against ragweed pollen reduced patients’ symptoms of allergic rhinitis by 60 per cent, they found.
The researchers created the vaccine by combining a ragweed-pollen antigen with a sequence of DNA that inhibits the immune response characteristic of allergy.
This vaccine requires a much shorter course of treatment than the three to five years that traditional immunotherapy requires.
The researchers then carried out a trial including 25 patients aged between 23 and 60 who were allergic to ragweed. They were randomly assigned to receive six weekly injections of either the ragweed vaccine or a placebo.
Following treatment, the patients underwent a ragweed challenge and their nasal secretions were tested for inflammatory markers. Their allergic symptoms were then monitored over two years.
The researchers found that the vaccine did not have the effect on albumin levels in nasal secretions after the ragweed challenge that had been anticipated.
However, the patients who received the vaccine had improved clinical outcomes compared to the control group.
The severity of their allergic rhinitis symptoms throughout the ragweed season was approximately a third of that experienced by the placebo group, as measured by a visual analogue chart.
This difference was maintained throughout the second ragweed season.
Lead researcher Dr Peter Creticos, medical director of the Johns Hopkins Asthma and Allergy Center in Baltimore, said: ‘This therapeutic intervention heralds a major advance in the treatment of allergic rhinitis.’