An African swine fever vaccine has shown positive early results in trials, the Chinese Academy of Agricultural Sciences (CAAS) said Wednesday.

The vaccine, developed by Harbin Veterinary Research Institute under the CAAS, uses a gene-deleted African swine fever virus as a live attenuated vaccine in pigs, and was approved for clinical trials in March.

Since April, clinical trials have been carried out in three breeding bases in Heilongjiang Province, Henan Province and Xinjiang Uygur Autonomous Region. Around 3,000 pigs received the vaccine.

So far, vaccinated piglets have normally grown and developed with no obvious adverse effects.

No pathological changes have been found in the anatomy of vaccinated pigs, and no obvious differences have been found between the vaccine group and the control group. The overall mortality rate is below 1 percent.

Tests for the vaccine's clinical efficacy are still underway.

African swine fever, first described in Kenya in 1921, is a highly contagious viral disease found in swine with mortality rates approaching 100 percent. Over the past decade, the disease has spread through many countries, posing a serious risk of further expansion.

With no vaccine or treatment available, culling pigs is the most effective way of containing outbreaks.

Last October, Chinese researchers reported in the journal Science that they unraveled the three-dimensional structure of the African swine fever virus, laying a solid foundation for developing effective and safe vaccines against the disease.