Moderate influenza vaccine effectiveness against A(H1N1)pdm09 virus, and low effectiveness against A(H3N2) subtype, 2018/19 season in Italy

Stefania Bellino, Antonino Bella, Simona Puzelli, Angela Di Martino, Marzia Facchini, Ornella Punzo, Patrizio Pezzotti, Maria Rita Castrucci, The InfluNet Study Group

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Influenza vaccines are updated every year to match the vaccine strains with currently circulating viruses; consequently influenza vaccine effectiveness (IVE) has to be assessed annually.Research design and methods: A test-negative case-control study was conducted within the context of the Italian sentinel influenza surveillance network to estimate IVE by age group, virus subtype, and vaccine brand in medically attended laboratory-confirmed influenza.Results: In Italy, the 2018/19 influenza season was characterized by the co-circulation of influenza A(H1N1)pdm09 and A(H3N2) viruses. The adjusted IVE estimate in preventing influenza was moderate (44.8%, 95% CI: 18.8 to 62.5) against A(H1N1)pdm09, whereas there was no evidence of effectiveness (1.8%, 95% CI: -37.8 to 30.1) in persons affected by A(H3N2). IVE against A(H1N1)pdm09 decreased with age ranging from 65.7% to 13.1% among children/adolescents and elderly, respectively; moreover results suggest that Vaxigrip Tetra® was more effective against A(H1N1)pdm09 compared to Fluarix Tetra® [62.5% (95% CI: 34.3 to 78.6) vs 24.5% (95% CI: -40.6 to 59.6)]. Low effectiveness (35.2%, 95% CI: -50.8 to 72.1) against A(H3N2) was detected only in the elderly immunized with Fluad®.Conclusions: Findings suggest that influenza vaccines were low to moderately effective, probably due to a mismatch between circulating and vaccine strains.

Original languageEnglish
Pages (from-to)1201-1209
Number of pages9
JournalExpert Review of Vaccines
Volume18
Issue number11
DOIs
Publication statusPublished - Nov 2019

Keywords

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Animals
  • Case-Control Studies
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Infant
  • Influenza A Virus, H1N1 Subtype/immunology
  • Influenza A Virus, H3N2 Subtype/immunology
  • Influenza Vaccines/administration & dosage
  • Influenza, Human/epidemiology
  • Italy/epidemiology
  • Male
  • Middle Aged
  • Treatment Outcome
  • Young Adult

Fingerprint Dive into the research topics of 'Moderate influenza vaccine effectiveness against A(H1N1)pdm09 virus, and low effectiveness against A(H3N2) subtype, 2018/19 season in Italy'. Together they form a unique fingerprint.

Cite this