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Effectiveness of influenza vaccine against laboratory-confirmed influenza, in the late 2011-2012 season in Spain, among population targeted for vaccination.
BMC Infect Dis. 2013 Sep 22; 13:441.BI

Abstract

BACKGROUND

In Spain, the influenza vaccine effectiveness (VE) was estimated in the last three seasons using the observational study cycEVA conducted in the frame of the existing Spanish Influenza Sentinel Surveillance System. The objective of the study was to estimate influenza vaccine effectiveness (VE) against medically attended, laboratory-confirmed influenza-like illness (ILI) among the target groups for vaccination in Spain in the 2011-2012 season. We also studied influenza VE in the early (weeks 52/2011-7/2012) and late (weeks 8-14/2012) phases of the epidemic and according to time since vaccination.

METHODS

Medically attended patients with ILI were systematically swabbed to collect information on exposure, laboratory outcome and confounding factors. Patients belonging to target groups for vaccination and who were swabbed <8 days after symptom onset were included. Cases tested positive for influenza and controls tested negative for any influenza virus. To examine the effect of a late season, analyses were performed according to the phase of the season and according to the time between vaccination and symptoms onset.

RESULTS

The overall adjusted influenza VE against A(H3N2) was 45% (95% CI, 0-69). The estimated influenza VE was 52% (95% CI, -3 to 78), 40% (95% CI, -40 to 74) and 22% (95% CI, -135 to 74) at 3.5 months, 3.5-4 months, and >4 months, respectively, since vaccination. A decrease in VE with time since vaccination was only observed in individuals aged ≥ 65 years. Regarding the phase of the season, decreasing point estimates were only observed in the early phase, whereas very low or null estimates were obtained in the late phase for the shortest time interval.

CONCLUSIONS

The 2011-2012 influenza vaccine showed a low-to-moderate protective effect against medically attended, laboratory-confirmed influenza in the target groups for vaccination, in a late season and with a limited match between the vaccine and circulating strains. The suggested decrease in influenza VE with time since vaccination was mostly observed in the elderly population. The decreasing protective effect of the vaccine in the late part of the season could be related to waning vaccine protection because no viral changes were identified throughout the season.

Authors+Show Affiliations

National Centre of Epidemiology, Institute of Health Carlos III, c/Monforte de Lemos no, 5, Madrid 28029, Spain. sjimenezj@isciii.es.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

24053661

Citation

Jiménez-Jorge, Silvia, et al. "Effectiveness of Influenza Vaccine Against Laboratory-confirmed Influenza, in the Late 2011-2012 Season in Spain, Among Population Targeted for Vaccination." BMC Infectious Diseases, vol. 13, 2013, p. 441.
Jiménez-Jorge S, de Mateo S, Delgado-Sanz C, et al. Effectiveness of influenza vaccine against laboratory-confirmed influenza, in the late 2011-2012 season in Spain, among population targeted for vaccination. BMC Infect Dis. 2013;13:441.
Jiménez-Jorge, S., de Mateo, S., Delgado-Sanz, C., Pozo, F., Casas, I., Garcia-Cenoz, M., Castilla, J., Pérez, E., Gallardo, V., Rodriguez, C., Vega, T., Quiñones, C., Martínez, E., Vanrell, J. M., Giménez, J., Castrillejo, D., Serrano, M. d. e. l. . C., Ramos, J. M., & Larrauri, A. (2013). Effectiveness of influenza vaccine against laboratory-confirmed influenza, in the late 2011-2012 season in Spain, among population targeted for vaccination. BMC Infectious Diseases, 13, 441. https://doi.org/10.1186/1471-2334-13-441
Jiménez-Jorge S, et al. Effectiveness of Influenza Vaccine Against Laboratory-confirmed Influenza, in the Late 2011-2012 Season in Spain, Among Population Targeted for Vaccination. BMC Infect Dis. 2013 Sep 22;13:441. PubMed PMID: 24053661.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effectiveness of influenza vaccine against laboratory-confirmed influenza, in the late 2011-2012 season in Spain, among population targeted for vaccination. AU - Jiménez-Jorge,Silvia, AU - de Mateo,Salvador, AU - Delgado-Sanz,Concha, AU - Pozo,Francisco, AU - Casas,Inmaculada, AU - Garcia-Cenoz,Manuel, AU - Castilla,Jesús, AU - Pérez,Esteban, AU - Gallardo,Virtudes, AU - Rodriguez,Carolina, AU - Vega,Tomás, AU - Quiñones,Carmen, AU - Martínez,Eva, AU - Vanrell,Juana María, AU - Giménez,Jaume, AU - Castrillejo,Daniel, AU - Serrano,María del Carmen, AU - Ramos,Julián Mauro, AU - Larrauri,Amparo, AU - ,, Y1 - 2013/09/22/ PY - 2013/05/10/received PY - 2013/09/13/accepted PY - 2013/9/24/entrez PY - 2013/9/24/pubmed PY - 2014/6/24/medline SP - 441 EP - 441 JF - BMC infectious diseases JO - BMC Infect. Dis. VL - 13 N2 - BACKGROUND: In Spain, the influenza vaccine effectiveness (VE) was estimated in the last three seasons using the observational study cycEVA conducted in the frame of the existing Spanish Influenza Sentinel Surveillance System. The objective of the study was to estimate influenza vaccine effectiveness (VE) against medically attended, laboratory-confirmed influenza-like illness (ILI) among the target groups for vaccination in Spain in the 2011-2012 season. We also studied influenza VE in the early (weeks 52/2011-7/2012) and late (weeks 8-14/2012) phases of the epidemic and according to time since vaccination. METHODS: Medically attended patients with ILI were systematically swabbed to collect information on exposure, laboratory outcome and confounding factors. Patients belonging to target groups for vaccination and who were swabbed <8 days after symptom onset were included. Cases tested positive for influenza and controls tested negative for any influenza virus. To examine the effect of a late season, analyses were performed according to the phase of the season and according to the time between vaccination and symptoms onset. RESULTS: The overall adjusted influenza VE against A(H3N2) was 45% (95% CI, 0-69). The estimated influenza VE was 52% (95% CI, -3 to 78), 40% (95% CI, -40 to 74) and 22% (95% CI, -135 to 74) at 3.5 months, 3.5-4 months, and >4 months, respectively, since vaccination. A decrease in VE with time since vaccination was only observed in individuals aged ≥ 65 years. Regarding the phase of the season, decreasing point estimates were only observed in the early phase, whereas very low or null estimates were obtained in the late phase for the shortest time interval. CONCLUSIONS: The 2011-2012 influenza vaccine showed a low-to-moderate protective effect against medically attended, laboratory-confirmed influenza in the target groups for vaccination, in a late season and with a limited match between the vaccine and circulating strains. The suggested decrease in influenza VE with time since vaccination was mostly observed in the elderly population. The decreasing protective effect of the vaccine in the late part of the season could be related to waning vaccine protection because no viral changes were identified throughout the season. SN - 1471-2334 UR - https://www.unboundmedicine.com/medline/citation/24053661/Effectiveness_of_influenza_vaccine_against_laboratory_confirmed_influenza_in_the_late_2011_2012_season_in_Spain_among_population_targeted_for_vaccination_ L2 - https://bmcinfectdis.biomedcentral.com/articles/10.1186/1471-2334-13-441 DB - PRIME DP - Unbound Medicine ER -