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Table 2 Hemagglutination inhibition (HI) antibody response against the recombinant A/Vietnam/1194/2004 vaccine strain

From: The safety and immunogenicity of a MF59-adjuvanted H5N1 prepandemic influenza vaccine in healthy adults primed with homologous or heterologous H5N1 vaccines: an observational study

  Participants without priming (n = 71) Participants primed with A/Indonesia/05/2005 (n = 34) Participants primed with A/Vietnam/1194/2004 and A/Indonesia/05/2005 (n = 26)
Base line    
GMTa 20 (14–29) 25 (17–39) 73 (40–133)
Seroprotective rateb (%) 49 (37–61) 59 (41–75) 73 (52–88)
Three weeks after 1 st immunization    
GMT 23 (16–34) 32 (20–51) 163 (91–290)
Seroprotective rate (%) 55 (43–67) 65 (46–80) 85 (65–96)
Seroconversion ratec (%) 8 (3–17) 9 (2–24) 27 (12–48)
Three weeks after 2 nd immunization    
GMT 29 (19–45) 41 (24–68) 176 (100–312)
Seroprotective rate (%) 63 (51–75) 68 (49–83) 88 (70–98)
Seroconversion rate (%) 21 (12–32) 21 (9–38) 35 (17–56)
  1. aGMT = geometric mean titer. A GMT of HI test result of a dilution of greater than 1:640 was recorded as a HI titer of 640.
  2. bSeroprotective rate is defined as the proportion of participants with a HI titer of 40 or greater.
  3. cSeroconversion rate is defined as the percentage of participants who have a HI titer of less than 10 before vaccination and a titer of more than 40 after vaccination or have a HI titer of more than 10 before vaccination and at least a four-fold increase in titer after vaccination.