Singapore researchers have developed an asthma vaccine using a dust mite gene, a newspaper reported on Monday. Most asthma sufferers in tropical and subtropical countries are allergic to dust mites, the Straits Times said. A 20-member research team at the National University of Singapore has finished testing the vaccine on mice, the report said. The researchers had removed a gene from dust mites and injected it into mice, which were later found to be immune to asthma-causing allergens, the paper quoted team leader Chua Kaw Yan as saying.