Abstract: Objective To evaluate the difference between two kinds of needle design for PFS (5B27G PFS and 3B25G PFS) in subject's pain level, nurse's insertion force and incidence of adverse events at the injection site during vaccination. Methods A randomized, double-blind, parallel-controlled clinical trial was designed. Six hundred and four subjects were randomly divided into two groups, the experimental group (n=299) used 5B27G PFS and the control group used 3B25G PFS for HAV vaccination; both groups vaccinated HBV using a 3B25G PFS as a self-control. The subjects were compared for the pain level, insertion force, and the adverse reactions at the injection site. Results VAS and C-PIVRS were used for HAV-injection pain level evaluation. Moderate to severe pain ration of the experimental group was respectively 7.02% and 16.55%; while in the control group, the results were 15.73% and 20.32%, respectively. The difference between groups was significant (all P≤0.001). The VAS score of insertion force was significantly higher in the control group than that in the experimental group (P<0.001). The incidence of skin adverse reactions in the experimental group was lower than that in the control group, which was 47.49% and 65.25%, respectively (P<0.001). Conclusion Compared with 3B25G PFS, the use of 5B27G PFS can significantly reduce the pain level, nurse's insertion force, and incidence of adverse events at the injection site during vaccination.