Figure 2. Neutralization activity of sera in the vaccinated cynomolgus macaques.

Sera were collected in the indicated weeks after the first vaccination. Sera of week 2 were obtained before the second vaccination. The neutralization titers against Hokkaido2 (A) and Narita1 (B) were expressed as reciprocals of dilution of the serum samples that showed CPE in 50% of the wells. Detection limits were 1∶8 in week 0 and 1∶4 in the other weeks. P values calculated with Student’s t-test are less than 0.05 in comparison between the whole particle vaccine group and split vaccine group against Hokkaido2 and Narita1 (*) when the titers below 1∶4 are calculated as 1∶4.