Cross-protection to new drifted influenza A(H3) viruses and prevalence of protective antibodies to seasonal influenza, during 2014 in Portugal.
Immune profile for influenza viruses is highly changeable over time. Serological studies can assess the prevalence of influenza, estimate the risk of infection, highlight asymptomatic infection rate and can also provide data on vaccine coverage. The aims of the study were to evaluate pre-existing cross-protection against influenza A(H3) drift viruses and to assess influenza immunity in the Portuguese population.



We developed a cross-sectional study based on a convenience sample of 626 sera collected during June 2014, covering all age groups, both gender and all administrative health regions of Portugal. Sera antibody titers for seasonal and new A(H3) drift influenza virus were evaluated by hemagglutination inhibition assay (HI). Seroprevalence to each seasonal influenza vaccine strain virus and to the new A(H3) drift circulating strain was estimated by age group, gender and region and compared with seasonal influenza-like illness (ILI) incidence rates before and after the study period.



Our findings suggest that seroprevalences of influenza A(H3) (39.9%; 95% CI: 36.2-43.8) and A(H1)pdm09 (29.7%; 95% CI: 26.3-33.4) antibodies were higher than for influenza B, in line with high ILI incidence rates for A(H3) followed by A(H1)pdm09, during 2013/2014 season. Low pre-existing cross-protection against new A(H3) drift viruses were observed in A(H3) seropositive individuals (46%). Both against influenza A(H1)pdm09 and A(H3) seroprotection was highest in younger than 14-years old. Protective antibodies against influenza B were highest in those older than 65years old, especially for B/Yamagata lineage, 33.3% (95% CI: 25.7-41.9). Women showed a high seroprevalence to influenza, although without statistical significance, when compared to men. A significant decreasing trend in seroprotection from north to south regions of Portugal mainland was observed.



Our results emphasize that low seroprotection increases the risk of influenza infection in the following winter season. Seroepidemiological studies can inform policy makers on the need for vaccination and additional preventive measures.
Instituto Nacional de Saúde Doutor Ricardo Jorge, I.P., Portugal. Electronic address: raquel.guiomar@insa.min-saude.pt.
Raquel
R
Guiomar
Instituto Nacional de Saúde Doutor Ricardo Jorge, I.P., Portugal. Electronic address: susana.pereira@insa.min-saude.pt.
Susana
S
Pereira da Silva
Instituto Nacional de Saúde Doutor Ricardo Jorge, I.P., Portugal. Electronic address: patricia.conde@insa.min-saude.pt.
Patrícia
P
Conde
Instituto Nacional de Saúde Doutor Ricardo Jorge, I.P., Portugal. Electronic address: paula.cristovao@insa.min-saude.pt.
Paula
P
Cristóvão
Instituto Nacional de Saúde Doutor Ricardo Jorge, I.P., Portugal. Electronic address: carinamaia04@gmail.com.
Ana Carina
AC
Maia
Instituto Nacional de Saúde Doutor Ricardo Jorge, I.P., Portugal. Electronic address: pedro.pechirra@insa.min-saude.pt.
Pedro
P
Pechirra
Instituto Nacional de Saúde Doutor Ricardo Jorge, I.P., Portugal. Electronic address: ana.rodrigues@insa.min-saude.pt.
Ana Paula
AP
Rodrigues
Instituto Nacional de Saúde Doutor Ricardo Jorge, I.P., Portugal. Electronic address: baltazar.nunes@insa.min-saude.pt.
Baltazar
B
Nunes
Administração Regional de Saúde do Algarve, I.P., Laboratório Regional de Saúde Pública Laura Ayres, Portugal. Electronic address: lmilho@arsalgarve.min-saude.pt.
Luís
L
Milho
Administração Regional de Saúde do Algarve, I.P., Laboratório Regional de Saúde Pública Laura Ayres, Portugal. Electronic address: acoelho@arsalgarve.min-saude.pt.
Ana Paula
AP
Coelho
Administração Regional de Saúde do Algarve, I.P., Laboratório Regional de Saúde Pública Laura Ayres, Portugal. Electronic address: afernandes@arsalgarve.min-saude.pt.
Aida
A
Fernandes
Centro Hospitalar de Coimbra, E.P.E., Portugal.
Paula
P
Caseiro
Centro Hospitalar de Coimbra, E.P.E., Portugal. Electronic address: imuno@huc.min-saude.pt.
Fernando
F
Rodrigues
Centro Hospitalar de Coimbra, E.P.E., Portugal. Electronic address: lurdescorreia@chc.min-saude.pt.
Lurdes
L
Correia
Centro Hospitalar de Coimbra, E.P.E., Portugal. Electronic address: joaovaz@huc.min-saude.pt.
João
J
Pereira-Vaz
Centro Hospitalar da Cova da Beira, E.P.E., Portugal. Electronic address: s.sofia.almeida@gmail.com.
Sofia
S
Almeida
Centro Hospitalar de Lisboa Central, E.P.E., Portugal. Electronic address: biomolecular@sapo.pt.
Paula
P
Branquinho
Centro Hospitalar de Lisboa Central, E.P.E., Portugal. Electronic address: rita.cortereal@chlc.min-saude.pt.
Rita
R
Côrte-Real
Centro Hospitalar Setúbal, E.P.E., Portugal.
Regina
R
Viseu
Centro Hospitalar Setúbal, E.P.E., Portugal. Electronic address: mjmperes@gmail.com.
Maria João
MJ
Peres
Hospital Central do Funchal, E.P.E., Portugal.
Raquel
R
Sanches
Hospital Central do Funchal, E.P.E., Portugal.
Filipa
F
Dantas
Hospital Central do Funchal, E.P.E., Portugal.
Ludovina
L
Freitas
Hospital Central do Funchal, E.P.E., Portugal. Electronic address: drgraca@sesaram.pt.
Graça
G
Andrade
Hospital do Espírito Santo, E.P.E., Évora, Portugal. Electronic address: mmaurilio@hevora.min-saude.pt.
Manuel
M
Maurílio
Hospital do Espírito Santo, E.P.E., Évora, Portugal. Electronic address: filomenacaldeira1@gmail.com.
Filomena
F
Caldeira
Hospital do Divino Espírito Santo de Ponta Delgada, E.P.E., Portugal. Electronic address: Rita.TR.Veloso@azores.gov.pt.
Rita
R
Cabral Veloso
Hospital do Divino Espírito Santo de Ponta Delgada, E.P.E., Portugal. Electronic address: Luisa.MQ.Vieira@azores.gov.pt.
Luisa
L
Mota-Vieira
Hospital do Santo Espírito de Angra do Heroísmo, E.P.E. and Institute for Molecular and Cell Biology (IBMC), University of Porto, Portugal.
Marta
M
Soares
Hospital do Santo Espírito de Angra do Heroísmo, E.P.E. and Institute for Molecular and Cell Biology (IBMC), University of Porto, Portugal. Electronic address: arcouto@seebmo.org.
Ana Rita
AR
Couto
Hospital do Santo Espírito de Angra do Heroísmo, E.P.E. and Institute for Molecular and Cell Biology (IBMC), University of Porto, Portugal. Electronic address: jacome@seebmo.org.
Jácome
J
Bruges-Armas
Hospital de São João, E.P.E., Portugal. Electronic address: rita_m_p@hotmail.com.
Rita Mouro
RM
Pinto
Hospital de São João, E.P.E., Portugal. Electronic address: jssimoes@hsjoao.min-saude.pt.
Joana
J
Sobrinho Simões
Hospital de São João, E.P.E., Portugal. Electronic address: mrsscosta@gmail.com.
Maria do Rosário
MDR
Costa
Hospital de São João, E.P.E., Portugal. Electronic address: jtguimar@med.up.pt.
João Tiago
JT
Guimarães
Instituto Português de Oncologia de Lisboa, Francisco Gentil, E.P.E., Portugal. Electronic address: lmartins@ipolisboa.min-saude.pt.
Luís
L
Martins
Instituto Português de Oncologia de Lisboa, Francisco Gentil, E.P.E., Portugal. Electronic address: mcunha@ipolisboa.min-saude.pt.
Mário
M
Cunha
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D056738:Cross Protection; D003430:Cross-Sectional Studies; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D009980:Influenza A virus / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D011174:Portugal / Q000453:epidemiology; D016036:Seroepidemiologic Studies; D055815:Young Adult
D000914:Antibodies, Viral
Cross-protection; Influenza; Seroepidemiologic studies; Seroprevalence