Effectiveness of the current and prior influenza vaccinations in Northern Spain, 2018-2019

Jesús Castilla; María Eugenia Portillo; Itziar Casado; Francisco Pozo; Ana Navascués; Marta Adelantado; Carlos Gómez Ibáñez; Carmen Ezpeleta; Iván Martínez-Baz; Primary Health Care Sentinel Network and Network for Influenza Surveillance in Hospitals of Navarre

doi:10.1016/j.vaccine.2020.01.028

Effectiveness of the current and prior influenza vaccinations in Northern Spain, 2018-2019

Vaccine. 2020 Feb 18;38(8):1925-1932. doi: 10.1016/j.vaccine.2020.01.028. Epub 2020 Jan 22.

Authors

Jesús Castilla¹, María Eugenia Portillo², Itziar Casado³, Francisco Pozo⁴, Ana Navascués², Marta Adelantado², Carlos Gómez Ibáñez⁵, Carmen Ezpeleta², Iván Martínez-Baz³; Primary Health Care Sentinel Network and Network for Influenza Surveillance in Hospitals of Navarre

Affiliations

¹ Instituto de Salud Pública de Navarra - IdiSNA, Pamplona, Spain; CIBER Epidemiología y Salud Pública (CIBERESP), Spain. Electronic address: jcastilc@navarra.es.
² Complejo Hospitalario de Navarra - IdiSNA, Pamplona, Spain.
³ Instituto de Salud Pública de Navarra - IdiSNA, Pamplona, Spain; CIBER Epidemiología y Salud Pública (CIBERESP), Spain.
⁴ CIBER Epidemiología y Salud Pública (CIBERESP), Spain; Centro Nacional de Microbiología (WHO National Influenza Centre - Madrid), Instituto de Salud Carlos III, Majadahonda, Spain.
⁵ Instituto de Salud Pública de Navarra - IdiSNA, Pamplona, Spain.

PMID: 31982263
DOI: 10.1016/j.vaccine.2020.01.028

Abstract

Background: The population targeted for influenza vaccination can be repeatedly vaccinated over successive seasons, and vaccines received in previous seasons may retain preventive effect. This study aims to estimate the effectiveness of inactivated influenza vaccines received in the current and prior seasons in the 2018-2019 season.

Methods: Influenza-like illness patients attended by sentinel general practitioners or admitted to hospitals in Navarre, Spain, were tested for influenza. Vaccination status in the current and three prior seasons was obtained from the vaccination registry. The test-negative design was used to estimate the vaccine effectiveness.

Results: A total of 381 influenza A(H1N1)pdm09 cases, 341 A(H3N2) cases and 1222 controls were analysed. As compared to individuals unvaccinated in the current and three prior seasons, the influenza vaccine effectiveness against A(H1N1)pdm09 was 57% (95% confidence interval [CI]: 40%, 70%) for current season vaccination regardless of prior doses and 48% (95%CI: 14%, 68%) for vaccination in prior seasons but not in the current season. These estimates were 12% (95%CI: -23%, 37%) and 27% (95%CI: -22%, 56%), respectively, against influenza A(H3N2). Individuals vaccinated with the two A(H1N1)pdm09 strains in influenza vaccines since 2009, A/Michigan/45/2015 and A/California/07/2009, had higher protection (68%; 95%CI: 53%, 77%) than those vaccinated with A/Michigan/45/2015 only (29%, p = 0.020) or with A/California/07/2009 only (34%, p = 0.005).

Conclusion: These results suggest moderate effectiveness of influenza vaccination against A(H1N1)pdm09 and low effectiveness against A(H3N2) influenza in the 2018-2019 season. Vaccination in prior seasons maintained a notable protective effect. Strains included in previous vaccines were as effective as the current vaccine strain, and both added their effects against influenza A(H1N1)pdm09.

Keywords: Case-control study; Influenza; Influenza vaccine; Influenza-like illness; Repeated vaccination; Vaccine effectiveness.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Case-Control Studies
Humans
Influenza A Virus, H1N1 Subtype
Influenza A Virus, H3N2 Subtype
Influenza Vaccines / administration & dosage*
Influenza, Human* / epidemiology
Influenza, Human* / prevention & control
Sentinel Surveillance
Spain / epidemiology
Treatment Outcome
Vaccination

Substances

Influenza Vaccines