OBJECTIVETo compare the reactogenicity and serology between influenza subunit vaccine and split vaccine.

METHODSA randomized, double-blind study was carried out among children (age 6 - 12 years) in order to compare the safety and immunogenicity of an influenza inactivated subunit vaccine (Agrippal, Chiron Vaccines) with that of a split vaccine (Flurix, GSK).

RESULTSA total of 499 subjects were vaccinated and included in the safety analysis. A total of 249 subjects received Agrippal and 250 received Flurix. All subjects were kept under medical observation for 30 minutes in order to check the evidence of having any immediate local and systemic reaction. Daily observation records were collected during the 3-day follow-up after vaccination. 6.4% of the cases with fever >or= 37.5 degrees C was reported in the Flurix group, but 2.4% in Agrippal group which was significantly less than the former group (P > 0.05). Blood samples (the D0 pre- and D23 post-vaccination sera) were collected from 224 of Agrippal group and 223 of Flurix group and analysed by the haemagglutination inhibition (HI) assay. Agrippal and Flurix induced similar seroprotection (HI titer >or= 1:40, H1N1 99.6% vs 100.0%; H3N2 99.1% vs 99.1%) and seroconversion (4-fold increase, 95.1% vs 97.8%; H3N2 74.5% vs 79.8%) rates and geometric mean titer (GMT) increase (16.0 vs 21.0; 5.4 vs 6.4) against the two A subtypes. A similar seroprotection rate (94.2% vs 96.4%) and GMT increase (21.2 vs 18.2) against the influenza B strain were also noticed in both vaccines. No significant difference was found in the results of immunological assay between the two vaccines (P < 0.05). A lower seroconversion rate against B strain was observed in Agrippal group than in Flurix group (91.1% vs 97.3%).

CONCLUSIONIn terms of safety, both vaccines were generally well tolerated. The fever reaction was less frequently seen in the Agrippal group. Both vaccines induced an effective immune response in the vaccines.