Influenza A (H3N2) Outbreak, Nepal

Abstract

Worldwide emergence of variant viruses has prompted a change in the 2005–2006 H3N2 influenza A vaccine strain.

Neutralizing and Hemagglutination-Inhibiting Activities of Antibodies Elicited by the 2004-2005 Influenza Vaccine against Drifted Viruses

“…In particular, during the early months of 2005, the Italian surveillance network observed the highest incidence in the Ն65-yearold group, since the surveillance network was established in 1999, and regional surveillances recorded lab-confirmed cases in immunized subjects as well as outbreaks in nursing homes where vaccine coverage was close to 100%, suggesting the possibility of suboptimal protection as concerns the A/H3N2 component in immunized subjects, as reported previously in other surveillances (6,10).…”

“…In particular, during the early months of 2005, the Italian surveillance network observed the highest incidence in the Ն65-yearold group, since the surveillance network was established in 1999, and regional surveillances recorded lab-confirmed cases in immunized subjects as well as outbreaks in nursing homes where vaccine coverage was close to 100%, suggesting the possibility of suboptimal protection as concerns the A/H3N2 component in immunized subjects, as reported previously in other surveillances (6,10).In the present study, the antibody responses induced by the Wyoming/3/03 2004-2005 vaccine strain against the homologous variant, the 2004-2005 field isolate, and a previously circulating strain were investigated by comparing the antibody responses using hemagglutination inhibition (HI) and neutralization tests.The serum samples from vaccinees used in the present study had been obtained in the course of a previous vaccination study including 20 free-dwelling elderly individuals aged Ͼ60 years. All subjects had been vaccinated with one dose of a commercial trivalent influenza subunit vaccine containing 15 g hemagglutinin from each component.…”

“…1, and the antigenic and molecular distances between the Wyoming/3/03 vaccine strain and Pan-field, Wyo-field, and Cal-field are shown in Table 1. The amino acid changes relative to Wyoming/3/03 observed in Pan-field and Cal-field that had a major impact on virus antigenicity are those in positions 155 and 156 (Pan-field) and in position 145 (Cal-field), which created an additional glycosylation site (6,10,14).HI and neutralization titers were transformed into binary logarithms and corrected for prevaccination state, as described by Beyer et al (8). The observed distributions were confirmed to be normally distributed by the one-sample KolmogorovSmirnov goodness of fit test procedure.…”

“…1, and the antigenic and molecular distances between the Wyoming/3/03 vaccine strain and Pan-field, Wyo-field, and Cal-field are shown in Table 1. The amino acid changes relative to Wyoming/3/03 observed in Pan-field and Cal-field that had a major impact on virus antigenicity are those in positions 155 and 156 (Pan-field) and in position 145 (Cal-field), which created an additional glycosylation site (6,10,14).…”

Longitudinal Analysis of Genotype Distribution of Influenza A Virus from 2003 to 2005

“…Our studies have examined the genomic evolution of influenza viruses that circulated in our setting over the past 2 years. This (8). Based on antigenic analyses, the concept of antigenic drift comprised of mutations in specific epitopes of the globular domain of the hemagglutinin is a well-recognized phenomenon (9).…”