Immune evaluation of needle-free injection for vaccination with inactivated Mycoplasma hyopneumoniae vaccine

Yi Jie; Luo Ying; Li Chengyi; Xiang Jun; Tan Suqiong; Du Deyan

doi:10.20154/j.cnki.issn1672-9692.2025.06.003

Abstract：This study aimed to evaluate the immune efficacy of needle-free injector vaccination with an inactivated Mycoplasma hyopneumoniae(Mhp)vaccine.A safety trial was first conducted using needle-free injection of vaccines with different adjuvants,in which ten healthy susceptible piglets(14～21 days old)were randomly divided into two groups(five piglets per group)immunized with either Mhp oil-adjuvanted vaccine SY202401 or aqueous-adjuvanted vaccine SY202402 at a dose of 0.2 mL/piglet,with continuous observation for one week post-vaccination.Subsequently,forty-five healthy susceptible piglets(14～21 days old)were randomly assigned to nine groups(five piglets per group)for efficacy evaluation across three dimensions:Adjuvant type(oil-adjuvanted SY202401,aqueous-adjuvanted SY202402,and saline),injection method(needle-free vs.needle injection),and immunization dose(single dose vs.three consecutive doses).Results showed that 72 hours after needle-free immunization with oil-adjuvanted vaccine SY202401,four piglets developed distinct nodules(1～3 cm diameter)at the injection site.These nodules gradually resolved by day 7.No significant redness,ulceration,suppuration,or nodules were observed in the aqueous-adjuvanted SY202402 group throughout the observation period.At day 14 post-vaccination,Group A(needle-free SY202401,0.2 mL×3 doses)showed marginally higher serum Mhp antibody levels than Group B(needle-free SY202402,0.2 mL×3 doses).By day 35,Group B exhibited extremely higher antibody levels than Group F(needle-injected SY202402,1 mL)(P<0.01),while Group A showed extremely higher levels than Group C(needle-free SY202401,0.2 mL single dose)(P<0.01),and Group B demonstrated extremely higher levels than Group D(needle-free SY202402,0.2 mL single dose)(P<0.01).Adjuvant type,injection method,and immunization dose had no significant effect on average daily weight gain(P>0.05).The study demonstrates that needle-free injection of aqueous-adjuvanted inactivated Mhp vaccine offers high safety and superior immunogenicity compared to conventional needle injection,while reducing vaccine consumption and production costs;further validation of its impact on porcine growth performance is recommended.