“…Although formalin-killed vaccines generally provide highly protective effects compared with those of subunit vaccines and DNA vaccines, the subunit and DNA vaccines may replace the original formalin-killed vaccines or inactivated vaccines due to their promising efficacy, which are similar to those of inactivated vaccines, and longer shelf life 18,33 . Evidence suggests that DNA and subunit vaccines can efficiently trigger the immune system and promote protective efficacy, with an RPS value greater than 50% 11,13,14,17 . Nevertheless, these vaccines have limitations, such as their mass production costs, and they may require various optimizations to obtain the highest stable storage conditions 18,41 .…”