What can we expect from the new ASF vaccine developed in China?

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Chen, W., Zhao, D., He, X., Liu, R., Wang, Z., Zhang, X., Li, F., Shan, D., Chen, H., Zhang, J., et al. (2020). A seven-gene-deleted African swine fever virus is safe and effective as a live attenuated vaccine in pigs. Sci China Life Sci 63, https://doi.org/10.1007/s11427-020-1657-9
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Any news appearing in the specialized press about the emergence of a possible vaccine against African swine fever grabs our attention, since this disease has turned Asian pig production "upside down" and threatens European production. A few days ago, a scientific article was published describing the creation of a possible virus that could be a candidate to produce a live attenuated vaccine to protect pigs from ASF. The candidate virus is a mutant of a field virus isolated from the Chinese clinical cases (HLJ/18) and therefore a variant of genotype 2 of the virus, the same one affecting Russia and some European countries. What is unique about the mutant however, is that not one gene, but seven, are removed from the pathogenic virus. This has made the mutant virus capable of protecting pigs when exposed to the Chinese wild virus strain, both intramuscularly and orally, without producing carriers. The viremia that occurs after vaccination is temporary and does not produce chronic carriers as was the case with the vaccine attempts of the 1960s. And, as if that were not enough, they have also managed to make possible its cultivation in pig bone marrow cells which, although it is not a cell culture, would allow for industrial production, since some 200,000 doses of vaccine could be produced from just one pig. In other words, to produce the doses of vaccine needed to vaccinate and revaccinate the pig population in China (today some 300 million), some 3,000 pigs would be enough.

Given the circumstances, it is possible that this virus will one day reach the Chinese market in the form of a vaccine, but is it possible that it will become available in Europe? It does not seem simple for a vaccine based on the mutant virus HLJ/18-7GD to be authorized in Europe. First of all, it would have to be proven that the virus in question is capable of protecting against the viral variant circulating in Europe. Secondly, it would have to be proven that, with the european variants, no carriers of the virus are produced after infection. Thirdly, the attenuated viral mutant would have to be approved in Europe, and it should be noted that the virus is very different from the field one in terms of the deletions to which it has been subjected; we are talking that it could be considered a genetically modified organism (GMO). Fourthly, the production system requiring live animals would also have to be authorized in accordance with our legislation. And last but not least, the vaccine has been developed for the purpose of protecting domestic pigs and therefore is to be administered via the intramuscular route. To authorize the use of such a vaccine would mean accepting that ASF is endemic in Europe (or in the countries where its use would be authorized) and so, for market purposes, Europe would be considered ASF positive, entailing commercial consequences.

The ASF situation in Europe is different from that in Asia. Here the main problem is wild boar infections and, occasionally, infections on commercial farms; whereas in Asia the problem has been quite the opposite. This is potentially the reason why we are unlikely to see HLJ/18-7GD on our markets.