[Safety and immunogenicity of seasonal inactivated influenza vaccine (split virion) and cross-reactive antibody responses to the H7N9 avian influenza virus].
OBJECTIVE
To evaluate the safety and immunogenicity of seasonal inactivated influenza vaccine (split virion) and to analyze its cross-reactive antibody responses to H7N9 avian influenza virus.


METHODS
An open-labeled clinical trial was carried out in infants aged 6-35 months, adults aged 18-60 years and the elderly aged >60 years. After vaccinations (one dose for adults and the elderly and two doses for infants), adverse events were observed. Serum samples were obtained before vaccination and 21 days after vaccination from adults and elderly subjects. Three types of antibody against seasonal influenza virus and antibody against H7N9 avian influenza virus were tested using microhemagglutination inhibition (HI) assay. Immunogenicity of the vaccine was evaluated based on the immunogenicity criteria for adults and the elderly, set by the Committee for Medicinal Products for Human Use (CHMP) for the European Medicines Agency.


RESULTS
A total of 202 subjects (65 infants, 69 adults and 68 elderly) were enrolled and injected for at least one dose. The overall rate of adverse events was 12.4% (25/202) and most of them were under systemic reaction. No serious adverse event was reported. Pre- and post-vaccination serum samples were collected from 124 subjects (64 adults, 60 elderly). After 21 days of vaccination, the sero-conversion rate, sero-protection rate, and geometric mean titer (GMT) ratio (post-/pre-vaccination) of antibody against seasonal influenza virus were 78.1%-90.6%, 92.2%-100.0% and 7.9-41.0 among adults while 66.7%-83.3%, 86.7%-100.0% and 5.7-20.4 among the elderly, respectively. However, after vaccination, both sero-conversion rate and sero-protection rate of antibody against H7N9 avian influenza virus among adults and the elderly became zero, with GMT ratio between 1.2 and 1.4.


CONCLUSIONS
This trial vaccine appeared to have good safety and immunogenicity but inducing no cross-reactive antibody response to H7N9 avian influenza virus.
Henan Provincial Center for Disease Control and Prevention, Zhengzhou 450016, China.
Wanshen
W
Guo
Henan Provincial Center for Disease Control and Prevention, Zhengzhou 450016, China.
Jin
J
Xu
Sinovac Biotech Co., Ltd.
Junyu
J
Wu
Henan Provincial Center for Disease Control and Prevention, Zhengzhou 450016, China.
Sheng
S
Zhao
Yuanyang Country Center for Disease Control and Prevention, Henan.
Hongxia
H
He
Yuanyang Country Center for Disease Control and Prevention, Henan.
Wenjun
W
Shi
Sinovac Biotech Co., Ltd.
Dan
D
Yu
Sinovac Biotech Co., Ltd.
Jing
J
Li
Sinovac Biotech Co., Ltd.
Hong
H
Gao
Sinovac Biotech Co., Ltd. Email: chenjt@sinovac.com.
Jiangting
J
Chen
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000097:blood; D000917:Antibody Formation; D002675:Child, Preschool; D003429:Cross Reactions; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007223:Infant; D064766:Influenza A Virus, H7N9 Subtype; D007252:Influenza Vaccines / Q000276:immunology / Q000627:therapeutic use*; D008875:Middle Aged; D015164:Vaccines, Inactivated / Q000276:immunology / Q000627:therapeutic use; D055815:Young Adult
D000914:Antibodies, Viral; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated