Long Term Persistence and Effect of a Booster Dose of the Japanese Encephalitis Vaccine IC51

Muut: IC51

In study IC51-305, subjects who had received IC51 in study IC51-304 were tested for seroconversion 6 months after the first vaccination. Subjects who had protective titers were again tested for persistence of immunity at 12 months after the first immunization,whereas subjects who had titers below the seroconversion threshold by Month 6 received a booster dose of 1x6 mcg IC51 at Month 11. Their immune response was also assessed at Month 12. Thereafter, subjects who had no protective titer by Month 12 received a booster dose of 1x6 mcg IC51 at Month 23, regardless of prior treatment; and neutralizing antibody titers were reassessed at Month 24. Subjects who had protective titers at month 12 did not receive a booster at Month 23, and their neutralizing antibody titer was also assessed at Month 24.

Biologinen: IC51

Muut nimet:

• Japanilainen enkefaliitti puhdistettu inaktivoitu rokote

Long Term Immunogenicity of IC51 Vaccine 24 Months After the Primary Vaccination

Seroprotection rate (SPR) (anti-JEV neutralizing antibody titer ≥ 1:10) 24 months (M24) after the primary vaccination - imputed; Persistence of immunogenicity (SPR) at M24 defined as:

• pos. (positive) (persistent): Subjects

  • with a non-missing, pos. seroconversion at D56 (Study IC51-304) and
  • without booster at M11 or M23 and
  • with non-missing, seroprotection (SP) pos. PRNT50 at M6 or M12 and
  • with non-missing, SP pos. PRNT50 at M24

• neg. (negative) (non-persistent): Subjects with

  • missing or neg. seroconversion at D56 (Study IC51-304) or
  • booster at M11 or at M23, or
  • non-missing, SP neg. PRNT50 at M6 or M12 or
  • missing PRNT50 at both M6 and M12 or
  • missing or SP neg. PRNT50 (serum dilution giving 50% reduction in plaques in a Plaque Reduction Neutralization Test) at M24

SPR 24 Months After the Primary Vaccination (Observed)

Persistence of immunogenicity (SPR) at M24 (observed) defined as :

• positive (persistent): Subjects

  • with a non-missing, positive seroconversion at D56 (Study IC51-304), and
  • who did not receive a booster dose at Visit 2 (M11) or Visit 4 (M23), and
  • with a non-missing, SP positive PRNT50 result at Visit 1 (M6) or Visit 3 (M12), and
  • with a non-missing, SP positive PRNT50 result at Visit 5 (M24)

• negative (non-persistent): Subjects

  • with missing or negative seroconversion at D56 (Study IC51-304), or
  • who did receive a booster dose at Visit 2 (M11) or at Visit 4 (M23), or
  • with a non-missing, SP negative PRNT50 result at Visit 1 (M6) or Visit 3 (M12), or
  • with a missing PRNT50 result at both Visit 1 (M6) and Visit 3 (M12), or
  • with a non-missing, SP negative PRNT50 result at Visit 5 (M24)

Persistent and Actual SPR 6, 12 and 24 Months After Primary Vaccination

Persistent and Actual GMT 6, 12 and 24 Months After Primary Vaccination

SCR 1 Month After the Booster Doses

GMT 1month After Booster Doses

Safety Profile of IC51