Long-term immunogenicity of a virosomal subunit inactivated influenza vaccine in children with asthma.
To evaluate long-term immunogenicity of a virosomal subunit inactivated influenza vaccine in children with asthma, a prospective study was conducted during 2005-2006 influenza season in six public pediatric clinics in Milan and surroundings, Northern Italy. A single dose (0.5 ml) of a virosomal subunit inactivated influenza vaccine (Inflexal V) was injected in 106 asthmatic children aged 3-9 years. Serum hemagglutinin inhibition antibody titers were determined against the recommended influenza strains A/New Caledonia (H1N1), A/California (H3N2), and B/Shanghai (B), at pre-vaccination and 1 and 6 months after vaccination. Seroconversion rate (95% CI) against the strains A/H1N1, A/H3N2 and B was, respectively, 78% (68.6-85.7), 57% (46.7-66.9) and 66% (55.8-71.2) at 1 month. Seroprotection (titer> or =40) rate for A/H1N1, A/H3N2 and B was, respectively, 87% (77.8-92.2), 82% (72.6-89.7) and 90% (82.6-94.8) at 1 month and 74% (64.3-82.3), 77% (67.5-84.8), and 77% (67.5-84.8) at 6 months. Seroprotection rate was high and persistent (>95%) in children with pre-existing antibodies (titer> or =10) at pre-vaccination for any specific strain. In children without pre-existing antibodies, seroprotection rate for A/H1N1, A/H3N2 and B was, respectively, 67.6%, 66.7% and 74.4% at 1 month, and 35.1%, 56.2% and 41.0% at 6 months after vaccination. Vaccine was well tolerated. These results indicate that in unvaccinated children with asthma vaccination with a single dose of virosomal-adjuvanted influenza vaccine is well tolerated and effective as a whole. However, while immunity response and persistence are excellently high in children with pre-existing antibodies, in children naive for the antigens the immune parameters are lower at 6 months after vaccination.
Zuccotti
Gianvincenzo
G
Department of Pediatrics, University of Milan, Luigi Sacco Hospital, Via GB Grassi 74, 20157 Milan, Italy. gianvincenzo.zuccotti@unimi.it
Amendola
Antonella
A
Viganò
Alessandra
A
Pariani
Elena
E
Zappa
Alessandra
A
Pogliani
Laura
L
Giacomet
Vania
V
Savarino
Antonino
A
Podestà
Alberto
A
Rottoli
Amilcare
A
Tanzi
Elisabetta
E
Zanetti
Alessandro
A
Radaelli
Giovanni
G
D000208:Acute Disease; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D001249:Asthma / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology; D009981:Influenza B virus / Q000276:immunology; D007252:Influenza Vaccines / Q000009:adverse effects / Q000737:chemistry / Q000276:immunology*; D011446:Prospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D015164:Vaccines, Inactivated / Q000009:adverse effects / Q000276:immunology*; D022223:Vaccines, Subunit / Q000009:adverse effects / Q000276:immunology*; D022701:Virosomes / Q000276:immunology*
D000914:Antibodies, Viral; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated; D022223:Vaccines, Subunit; D022701:Virosomes