A vaccine developed in China for African swine fever, which devastated the country's pig herd and caused pork prices to soar, is progressing smoothly, according to results reported on Wednesday.

The widespread outbreak of swine fever since August 2018 has disrupted the supply of pork in China, where it is a staple meat, with millions of animals culled. The disease wiped out about 40 percent of the country's pig herd, causing prices to rocket as officials struggled to stabilise supplies.

Authorities have since been looking into means of preventing the disease, and the vaccine strain passed a national review in December 2019, according to a report by the China Science Daily posted on the website of the Chinese Academy of Agricultural Sciences (CAAS).

In March, the vaccine was approved by the agriculture ministry for clinical trials in northern Heilongjiang province, central Henan province and northwest Xinjiang region. Clinical trials of the vaccine developed by the Harbin Veterinary Research Institute were seeing "smooth progress", according to the CAAS.

About 3,000 pigs are involved in the ongoing trials, launched between April and June, with the animals in "good condition", said the report. Vaccinated sows have not shown abnormal clinical conditions or miscarriages, and the pigs have not made any toxic discharge of the vaccine.

Since immunisation, the fatality rate has been under one percent, and the immunised herd has not shown significant differences to the control group. The CAAS is expected to "accelerate the development of the vaccine" in the next step.