HANOI (Reuters) – Vietnam said on Tuesday it has had initial success in creating a vaccine to fight African swine fever, which has infected farms throughout the Southeast Asian country and prompted the culling of around 10% of its pig herd.

African swine fever – which has spread to Laos and North Korea as well after being detected in China in August 2018 – was first detected in Vietnam in February and has spread to farms in 61 of the country’s 63 provinces.

More than 2.9 million pigs have been culled in Vietnam, Agriculture Minister Nguyen Xuan Cuong said on Tuesday, out of a hog population of about 30 million.

“I think we’re on the right track, and we will soon have a vaccine,” Cuong said, according to the official Vietnam News Agency (VNA).

The vaccine, developed at the Vietnam National University of Agriculture, has been tested in its laboratory and at three farms in northern Vietnam, state broadcaster Vietnam Television (VTV) said in a separate report on Tuesday.

Experts on vaccines and African swine fever, though, were skeptical over the claims of progress and said there needed to be much more research to prove the viability of any vaccine.

“We need different phases of clinical trials, first in an experimental setting with controlled exposure, and then a field trial with natural exposure to the virus, and that cannot be a small trial,” said Dirk Pfeiffer, a professor of veterinary epidemiology at the City University of Hong Kong.

The complex nature of the virus and gaps in knowledge concerning infection and immunity have so far hindered other global efforts to develop a vaccine against the disease, which is harmless to humans but deadly to pigs.

Researchers elsewhere have abandoned attempts to use a killed virus for a vaccine and teams in the United States, Europe and China have been working on live vaccines instead, which carry higher safety risks.

In Vietnam’s initial trials, 31 out of 33 pigs injected with the test vaccine are still healthy after receiving two shots over a period of months, according to the VTV report.

Other pigs at the farms have died from the virus, the report said, without giving specific figures. No further details were given about the vaccine or the trials.

The agricultural university’s director, Nguyen Thi Lan, said the vaccine still needed further research, and required testing on a larger scale.

Lan declined to comment on the report and referred questions from Reuters to the agricultural ministry, which did not immediately respond to a request for comment.

Pork makes up three-quarters of total meat consumption in Vietnam, a country of 95 million people where most of its farm-raised pigs are consumed domestically.

The country’s pork industry is valued at 94 trillion dong ($4 billion) a year, and accounts for nearly 10% of Vietnam’s agricultural sector.

African swine fever was first detected in Asia last year in China, the world’s largest pork producer. As many as half of China’s breeding pigs have died or been slaughtered because of the disease, twice as many as officially reported.

(Reporting by Khanh Vu and Phuong Nguyen in HANOI; Additional reporting by Dominique Patton in BEIJING; Editing by James Pearson and Tom Hogue)