1.

Eurosurveillance, Volume 18, Issue 5, 31 January 2013

Surveillance and outbreak reports

Low and decreasing vaccine effectiveness against influenza A(H3) in 2011/12 among vaccination target groups in Europe: results from the I-MOVE multicentre case–control study

E Kissling¹, M Valenciano¹, A Larrauri², B Oroszi³, J M Cohen⁴, B Nunes⁵, D Pitigoi^6,7, C Rizzo⁸, J Rebolledo^9,10, I Paradowska-Stankiewicz¹¹, S Jiménez-Jorge², J K Horváth³, I Daviaud⁴, R Guiomar⁵, G Necula⁶, A Bella⁸, J O’Donnell⁹, M Głuchowska¹¹, B C Ciancio¹², A Nicoll¹², A Moren¹

1. EpiConcept, Paris, France
2. National Centre for Epidemiology, Instituto de Salud Carlos III, Madrid, Spain
3. Office of the Chief Medical Officer, Budapest, Hungary
4. GROG/Open Rome, Paris, France
5. Instituto Nacional de Saude Dr Ricardo Jorge, Lisbon, Portugal
6. Cantacuzino Institute, National Institute of Research – Development for Microbiology and Immunology, Bucharest, Romania
7. Universitatea de Medicina si Farmacie Carol Davila, Bucharest, Romania
8. National Centre for Epidemiology, Surveillance and Health Promotion, Istituto Superiore di Sanità, Roma, Italy
9. Health Protection Surveillance Centre, Dublin, Ireland
10. European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden
11. National Institute for Public Health, Warsaw, Poland
12. European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden

Abstract: Within the Influenza Monitoring Vaccine Effectiveness in Europe (I-MOVE) project we conducted a multicentre case–control study in eight European Union (EU) Member States to estimate the 2011/12 influenza vaccine effectiveness against medically attended influenza-like illness (ILI) laboratory-confirmed as influenza A(H3) among the vaccination target groups. Practitioners systematically selected ILI / acute respiratory infection patients to swab within seven days of symptom onset. We restricted the study population to those meeting the EU ILI case definition and compared influenza A(H3) positive to influenza laboratory-negative patients. We used logistic regression with study site as fixed effect and calculated adjusted influenza vaccine effectiveness (IVE), controlling for potential confounders (age group, sex, month of symptom onset, chronic diseases and related hospitalisations,  number of practitioner visits in the previous year). Adjusted IVE was 25% (95% confidence intervals (CI): -6 to 47) among all ages (n=1,014), 63% (95% CI: 26 to 82) in adults aged between 15 and 59 years and 15% (95% CI: -33 to 46) among those aged 60 years and above. Adjusted IVE was 38% (95%CI: -8 to 65) in the early influenza season (up to week 6 of 2012) and -1% (95% CI: -60 to 37) in the late phase. The results suggested a low adjusted IVE in 2011/12. The lower IVE in the late season could be due to virus changes through the season or waning immunity. Virological surveillance should be enhanced to quantify change over time and understand its relation with duration of immunological protection. Seasonal influenza vaccines should be improved to achieve acceptable levels of protection.

2.

Eurosurveillance, Volume 18, Issue 5, 31 January 2013

Surveillance and outbreak reports

Vaccine effectiveness of 2011/12 trivalent seasonal influenza vaccine in preventing laboratory-confirmed influenza in primary care in the United Kingdom: evidence of waning intra-seasonal protection

R G Pebody¹, N Andrews¹, J McMenamin², H Durnall³, J Ellis⁴, C I Thompson⁴, C Robertson^5,6, S Cottrell⁷, B Smyth⁸, M Zambon⁴, C Moore⁷, D M Fleming³, J M Watson¹

1. Health Protection Agency Health Protection Services – Colindale, London, United Kingdom
2. Health Protection Scotland, Glasgow, United Kingdom
3. Royal College of General Practitioners Research and Surveillance Centre, Birmingham, United Kingdom
4. Health Protection Agency Microbiology Services – Colindale, London, United Kingdom
5. University of Strathclyde, Glasgow, United Kingdom
6. International Prevention Research Institute, Lyon, France
7. Public Health Wales, Cardiff, United Kingdom
8. Public Health Agency Northern Ireland, Belfast, United Kingdom

Abstract: The 2011/12 season was characterised by unusually late influenza A (H3N2) activity in the United Kingdom (UK). We measured vaccine effectiveness (VE) of the 2011/12 trivalent seasonal influenza vaccine (TIV) in a test-negative case–control study in primary care. Overall VE against confirmed influenza A (H3N2) infection, adjusted for age, surveillance scheme and month, was 23% (95% confidence interval (CI): -10 to 47). Stratified analysis by time period gave an adjusted VE of 43% (95% CI: -34 to 75) for October 2011 to January 2012 and 17% (95% CI: -24 to 45) for February 2012 to April 2012. Stratified analysis by time since vaccination gave an adjusted VE of 53% (95% CI: 0 to 78) for those vaccinated less than three months, and 12% (95% CI: -31 to 41) for those vaccinated three months or more before onset of symptoms (test for trend: p=0.02). For confirmed influenza B infection, adjusted VE was 92% (95% CI: 38 to 99). A proportion (20.6%) of UK influenza A(H3N2) viruses circulating in 2011/12 showed reduced reactivity (fourfold difference in haemagglutination inhibition assays) to the A/Perth/16/2009 2011/12 vaccine component, with no significant change in proportion over the season. Overall TIV protection against influenza A(H3N2) infection was low, with significant intraseasonal waning.

3.

Eurosurveillance, Volume 18, Issue 5, 31 January 2013

Surveillance and outbreak reports

Decline in influenza vaccine effectiveness with time after vaccination, Navarre, Spain, season 2011/12

J Castilla^1,2, I Martínez-Baz^1,2, V Martínez-Artola³, G Reina⁴, F Pozo⁵, M García Cenoz^1,2, M Guevara^1,2, J Morán⁶, F Irisarri^1,2, M Arriazu^1,2, E Albéniz⁶, C Ezpeleta³, A Barricarte^1,2, Primary Health Care Sentinel Network⁷, Network for Influenza Surveillance in Hospitals of Navarre⁷

1. Instituto de Salud Pública de Navarra (Public Health Institute of Navarre), Pamplona, Spain
2. Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP; Network of Biomedical Research Centers Epidemiology and Public Health), Spain
3. Complejo Hospitalario de Navarra (Hospital complex of Navarre), Pamplona, Spain
4. Clínica Universidad de Navarra (University Clinic of Navarre), Pamplona, Spain
5. National Centre of Microbiology (World Health Organization National Influenza Centre - Madrid), Instituto de Salud Carlos III, Majadahonda, Spain
6. Primary Healthcare Directorate, Navarre Health Service, Pamplona, Spain
7. The members of these networks are listed at the end of the article

Abstract: This study evaluates the influenza vaccine effectiveness (VE) in preventing laboratory-confirmed cases in Navarre, Spain, in the 2011/12 season in which the peak was delayed until week 7 of 2012. We conducted a test-negative case–control study. Patients with influenza-like illness in hospitals and primary healthcare were swabbed for testing by reverse transcription-polymerase chain reaction. Influenza vaccination status and other covariates were obtained from healthcare databases. The vaccination status of confirmed cases and negative controls was compared after adjusting for potential confounders. VE was calculated as (1-odds ratio)x100. The 411 confirmed cases (93% influenza A(H3)) were compared with 346 controls. Most characterised viruses did not match the vaccine strains. The adjusted estimate of VE was 31% (95% confidence interval (CI): -21 to 60) for all patients, 44% (95% CI: -11 to 72) for those younger than 65 years and 19% (95% CI: -146 to 73) for those 65 or older. The VE was 61% (95% CI: 5 to 84) in the first 100 days after vaccination, 42% (95% CI: -39 to 75) between 100 and 119 days, and zero thereafter. This decline mainly affected people aged 65 or over. These results suggest a low preventive effect of the 2011/12 seasonal influenza vaccine, and a decline in VE with time since vaccination.