Protective Efficacy of Seasonal Influenza Vaccination against Seasonal and Pandemic Influenza Virus Infection during 2009 in Hong Kong

• Published in: Clinical infectious diseases Vol. 51; no. 12; pp. 1370 - 1379
• Main Authors: Cowling, Benjamin J., Ng, Sophia, Ma, Edward S. K., Cheng, Calvin K. Y., Wai, Winnie, Fang, Vicky J., Chan, Kwok-Hung, Ip, Dennis K. M., Chiu, Susan S., Peiris, J. S. Malik, Leung, Gabriel M.
• Format: Journal Article
• Language: English
• Published: Oxford The University of Chicago Press 15.12.2010; University of Chicago Press; Oxford University Press; Oxford University Press (OUP)
• Subjects: Adolescent; Antibodies; Antibodies, Neutralizing; Antibodies, Neutralizing - blood; Antibodies, Viral; Antibodies, Viral - blood; ARTICLES AND COMMENTARIES; Biological and medical sciences; Child; Children; Cross Protection; Female; Hemagglutination Inhibition Tests; Hong Kong; Hong Kong - epidemiology; Human viral diseases; Humans; Immunization; Infections; Infectious diseases; Influenza A virus; Influenza Vaccines; Influenza Vaccines - administration & dosage; Influenza Vaccines - immunology; Influenza, Human; Influenza, Human - epidemiology; Influenza, Human - prevention & control; Influenza, Human - virology; Life Sciences; Male; Medical sciences; Microbiology and Parasitology; Multivariate analysis; Neutralization Tests; Nose; Nose - virology; Orthomyxoviridae; Orthomyxoviridae - isolation & purification; Pandemics; Pharynx; Pharynx - virology; Placebos; Placebos - administration & dosage; Polymerase chain reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Viral; RNA, Viral - genetics; RNA, Viral - isolation & purification; School age children; Swine flu; Vaccination; Vaccination - methods; Vaccines; Vaccines, Inactivated; Vaccines, Inactivated - administration & dosage; Vaccines, Inactivated - immunology; Viral diseases; Viral diseases of the respiratory system and ent viral diseases; Viral infections; Virology; Viruses; Hong Kong; Asia; China; Infection; Prevention; Immunoprophylaxis; Seasonal variation; Viral disease; Influenza; Vaccination; Epidemiology
• ISSN: 1058-4838; 1537-6591; 1537-6591
• DOI: 10.1086/657311

Background. The relationship between seasonal influenza vaccine and susceptibility to 2009 pandemic A/H1N1 virus infection is not fully understood. Methods. One child 6–15 years of age from each of 119 households was randomized to receive 1 dose of inactivated trivalent seasonal influenza vaccine (TIV) or saline placebo in November 2008. Serum samples were collected from study subjects and their household contacts before and 1 month after vaccination (December 2008), after winter (April 2009) and summer influenza (September–October 2009) seasons. Seasonal and pandemic influenza were confirmed by serum hemagglutinination inhibition, viral neutralization titers, and reverse-transcription polymerase chain reaction performed on nasal and throat swab samples collected during illness episodes. Results. TIV recipients had lower rates of serologically confirmed seasonal A/H1N1 infection (TIV group, 8%; placebo group, 21%; P = .10) and A/H3N2 infection (7% vs 12%; P = .49), but higher rates of pandemic A/H1N1 infection (32% vs 17%; P = .09). In multivariable analysis, those infected with seasonal influenza A during the study had a lower risk of laboratory-confirmed pandemic A/H1N1 infection (adjusted odds ratio [OR], 0.35; 95% confidence interval [CI], 0.14–0.87), and receipt of seasonal TIV was unassociated with risk of pandemic A/H1N1 infection (adjusted OR, 1.11; 95% CI, 0.54–2.26). Conclusions. TIV protected against strain-matched infection in children. Seasonal influenza infection appeared to confer cross-protection against pandemic influenza. Whether prior seasonal influenza vaccination affects the risk of infection with the pandemic strain requires additional study. Clinical trials registration. ClinicalTrials.gov number NCT00792051.