AVAC's African swine fever vaccine has not been officially released

Vietnam veterinary - Undeniable wisdom and valor

“Creating a vaccine against African swine fever (ASF) is a difficult matter not only for Vietnam but also the whole world. And so, the discovery of a vaccine is an affirmation of wisdom and valor of the Vietnamese veterinary force", said Deputy Minister Phung Duc Tien at the concluding session of the meeting on May 30 concerning the review of circulation registration dossier for the ASF vaccine researched by Avac Vietnam Company Limited (AVAC Co.).

However, before officially releasing this vaccine, Deputy Minister Tien noted that AVAC needed to further perfect its documents, research methods, and most importantly, the comments of scientists during the meeting.

The leader of Ministry of Agriculture and Rural Development claimed to have faith in the three scientific councils participating in the evaluation of AVAC ASF LIVE vaccine although there were also some opinions outside the council that seemed to take a more cautious stance.

Dr. Dau Ngoc Hao, Chairman of the Vietnam Veterinary Association, said that the ASF vaccine application review was very different from the procedure for reviewing other vaccine applications because this was a very new vaccine that no countries had yet announced official commercial release.

“If it was in the past, we only needed to conduct tests on 40 pigs, but now we have conducted tests on a fair number of breeding facilities to calculate the probability of errors better. The number of review board members is also expanded, for example, by inviting more vaccine manufacturers to present the results and be evaluated through two counterarguments.

“The management unit sends assessment notes to each member of the board, also unlike before when just giving counterargument is enough. This time, each member expressed his opinion about the remaining uncertain issues in the dossier to make it clearer and ensure objectivity. When testing a narrow area, the review board also invites a diagnostic center to take samples to monitor the results very closely. The procedures are almost double that of a normal vaccine,” said Dr. Dau Ngoc Hao.

Previously in the discussion, the representative of the Sub-Department of Animal Health Region I noted that pigs with underlying diseases might die after vaccination, so further tests were essential.

AVAC ASF LIVE vaccine is proven to be protective in vaccinated pigs

According to the Central Veterinary Diagnostic Center, the narrow-scope vaccination trial was carried out at four pig farms with a herd size of 300 to 20,000 heads, including both pigs and sows. The pig farms were located in Luc Ngan and Son Dong districts; Bac Giang province; Hanoi’s Chuong My district and Ba Vi district.

The attenuated AVAC ASF LIVE vaccine contained a live attenuated virus strain produced on a cell medium. The vaccine was administered according to the manufacturer's recommendations with one dose for every tested pig.

The Central Veterinary Diagnostic Center took five pigs at random from each trial farm for initiating “strong virus attacks” on day 28 after vaccination. The Center also took five more pigs (not vaccinated) to conduct the control experiment.

The control pigs showed clinical symptoms on the 2nd - 3rd day after infection. The display included high fever, red and hot skin, decreased appetite. The pigs stopped eating for the next 3-5 days. The average body temperature rose to 41 oC.

On the 6th day after the strong poison attack, all five control pigs died. The autopsy results of the carcass showed typical lesions of ASF such as enlarged lymph nodes, heavy bleeding; hemorrhagic spleen bleeding black blood; pneumonia and heavy bleeding; myocardial and endocardial hemorrhage; renal pelvis hemorrhage.

On the other hand, pigs vaccinated with AVAC ASF LIVE showed mild clinical manifestations after being infected with the virulent ASF virus. Most of the clinical conditions were mild, only fever and a decrease in appetite for a few days, then the pigs quickly recovered to normal.

Fever in vaccinated pigs did not occur simultaneously. It appeared in some pigs during the entire follow-up period. There were also some cases of repeated fever.

In the report of the results, the Central Veterinary Diagnostic Center said that only one vaccinated pig died after being injected with the virus. This pig died on the 8th day after the strong virus attacks. The clinical manifestations and lesions were typical of ASF, similar to the control pigs. All remaining vaccinated pigs, a total of 19, had some mild clinical symptoms but all recovered and survived after the 21 days of follow-up.

The Central Veterinary Diagnostic Center concluded: 100% of control pigs (5 pigs) that were not vaccinated all died within nine days of being infected with the virulent ASF virus. Vaccinated pigs had an average survival rate of 95% (19/20 pigs). AVAC ASF LIVE vaccine was deemed to have a protective effect on vaccinated pigs.