Virological data integration on influenza vaccine effectiveness, Portugal 2015/16

• Main Author: Rodrigues, Ana Paula
• Publication Date: 2016
• Other Authors: Pechirra, Pedro, Guiomar, Raquel, Conde, Patrícia, Gomez, Verónica, Nunes, Baltazar, Machado, Ausenda
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10400.18/4269
• topic: Estados de Saúde; Gripe; EuroEVA; Infecções Respiratórias; Influenza; Vaccine Effectiveness; 2015-2016; Portugal

Regarding the wide genetic and antigenic variability of influenza viruses, overall or subtype influenza vaccine effectiveness (IVE) estimates may not be sufficient to assess vaccine protection against circulating strains. This is particularly important when low VE against a specific clade is suspicious or a new drifted virus is emerging. Viral genetic characterization is routinely performed in influenza surveillance but viruses are selected according patient age, severity and vaccine status. For instance, last season genetic characterized cases were more vaccinated than those not selected. A protocol for virological data integration on IVE studies within I-MOVE network was performed. It intended to solve the following issues: 1. Selection of the clade of interest to provide IVE; 2. Determination of the number of cases needed for genetic characterization; 3. Selection of cases for genetic characterization independently of patient features. During the 2015/16 season, a closely contact between epidemiological and laboratorial teams allows to perform a random selection of influenza cases for genetic characterization independently of cases features. Influenza A(H1N1)pdm09 was the selected subtype given its predominance and the emergence of new subclades (6B.1 and 6B.2). 52.2% of A(H1)pdm09 cases were successfully characterized. No differences regarding age, sex and vaccine status were found between selected and unselected cases for genetic characterization. The large sample size needed to estimate IVE against a specific clade requires an important effort on genetic characterization behind virological surveillance. However, random selection of cases for genetic characterization along season seems to be feasible without interfering with virological surveillance and obtains a representative sample of cases of the clade of interest. Virological data from randomly selected cases will permit to estimate IVE against a specific clade during influenza season. An extra effort on influenza genetic characterization is needed to achieve the needed sample size.