Influenza vaccination of healthcare workers: Critical analysis of the evidence for patient benefit underpinning policies of enforcement

PLoS ONE

Volumn 12, Issue 1, 2017, Pages

  De Serres, Gaston ^a,b   Skowronski, Danuta M ^c,d   Ward, Brian J ^e   Gardam, Michael ^f   Lemieux, Camille ^f   Yassi, Annalee ^d   Patrick, David M ^c,d   Krajden, Mel ^c,d   Loeb, Mark ^g   Collignon, Peter ^h,i   Carrat, Fabrice ^j,k,l  

^a INSTITUT NATIONAL DE SANTÉ PUBLIQUE DU QUÉBEC   (Canada)

^b UNIVERSITÉ LAVAL   (Canada)

^c BRITISH COLUMBIA CENTRE FOR DISEASE CONTROL   (Canada)

^d UNIVERSITY OF BRITISH COLUMBIA   (Canada)

^e RESEARCH INSTITUTE OF THE MCGILL UNIVERSITY HEALTH CENTRE   (Canada)

^f UNIVERSITY OF TORONTO   (Canada)

^g MCMASTER UNIVERSITY   (Canada)

^h AUSTRALIAN NATIONAL UNIVERSITY   (Australia)

ⁱ CANBERRA HOSPITAL   (Australia)

^j INSERM   (France)

^k SORBONNE UNIVERSITÉ   (France)

^l HÔPITAL SAINT ANTOINE   (France)

more..

Author keywords

[No Author keywords available]

Indexed keywords

INFLUENZA VACCINE;

ARTICLE; CLINICAL EFFECTIVENESS; EVIDENCE BASED MEDICINE; HEALTH CARE FACILITY; HEALTH CARE PERSONNEL; HEALTH CARE POLICY; HEALTH CARE PRACTICE; HOSPITAL INFECTION; HUMAN; INFECTION RISK; INFLUENZA; INFLUENZA VACCINATION; MORTALITY RATE; PATIENT CARE; POPULATION RISK; PREDICTIVE VALUE; PREVENTIVE MEDICINE; RANDOMIZED CONTROLLED TRIAL (TOPIC); RISK ASSESSMENT; RISK REDUCTION; CROSS INFECTION; INFLUENZA, HUMAN; LONG TERM CARE; MORTALITY; ORTHOMYXOVIRIDAE; PANDEMIC; PATHOGENICITY; PROCEDURES; VACCINATION; VIROLOGY;

CROSS INFECTION; HEALTH PERSONNEL; HUMANS; INFLUENZA VACCINES; INFLUENZA, HUMAN; LONG-TERM CARE; MORTALITY; ORTHOMYXOVIRIDAE; PANDEMICS; RANDOMIZED CONTROLLED TRIALS AS TOPIC; VACCINATION;

EID: 85011079646     PISSN: None     EISSN: 19326203     Source Type: Journal    
DOI: 10.1371/journal.pone.0163586     Document Type: Article

References (82)

1. World Health Organization, Meeting of the Strategic Advisory Group of Experts on immunization, April 2012 -conclusions and recommendations. Wkly Epidemiol Rec 2012; 87: 207-208. Available: Http://www.who.int/wer/2012/wer8721.pdf?ua=1.
2. Mereckiene J, Cotter S, Nicoll A, Lopalco P, Noori T, Weber JT et al. Seasonal influenza immunization in Europe. Overview of recommendations and vaccination coverage for three seasons: Pre-pandemic (2008/09), pandemic (2009/10) and post-pandemic (2010/11). Euro Surveill. 2014; 19(16): Pii = 20780. Available: Http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20780
3. United States Centers for Disease Control and Prevention. Immunization of health-care personnel. Recommendations of the Advisory Committee on Immunization Practices (ACIP). Morb Mortal Wkly Rep 2011; 60: 8-10
4. United States Centers for Disease Control and Prevention. Prevention and control of seasonal influenza with vaccines. Recommendations of the Advisory Committee on Immunization PracticesUnited States, 2013-2014. Morb Mortal Wkly Rep. 2013; 62: 28-29.
5. Public Health Agency of Canada. An Advisory Committee Statement (ACS)National Advisory Committee on Immunization (NACI), Statement on seasonal influenza vaccine for 2014-2015. Available: Http://www.phac-aspc.gc.ca/naci-ccni/assets/pdf/flu-grippe-eng.
6. New York State Department of Health. Regulation for prevention of influenza transmission by healthcare and residential facility and agency personnel. Prevention of influenza transmission by healthcare and residential facility and agency personnel. Available: Https://www.health.ny.gov/diseases/communicable/influenza/seasonal/providers/prevention-of-influenza-transmission/.
7. Ksienski DS. Mandatory seasonal influenza vaccination or masking of British Columbia health care workers: Year 1. Can J Pub Health 2014; 105: E312-e316.
8. Talbot T, Schaffner W. Commentary: On being the first. Infect Control Hosp Epidemiol 2010; 31: 889-892. doi: 10.1086/656211 PMID: 20653446
9. Babcock M, Gemeinhart N, Jones M, Dunagan W, Woeltje K. Mandatory influenza vaccination of health care workers: Translating policy to practice. Clin Infect Dis 2010; 50: 459-464. doi: 10.1086/650752 PMID: 20064039
10. Immunization Action Coalition. Honor roll for patient safety. Available: Http://www.immunize.org/laws/influenzahcw.asp.
11. Potter J, Stott DJ, Roberts MA, Elder AG, O'Donnel B, Knight PV, et al. Influenza vaccination of health care workers in long-term-care hospitals reduces the mortality of elderly patients. J Infect Dis 1997; 175: 1-6. PMID: 8985189
12. Carman WF, Elder AG, Wallace LA, McAulay K, Walker A, Murray GD, et al. Effects of influenza vaccination of health-care workers on mortality of elderly people in long-term care: A randomised controlled trial. Lancet 2000; 355: 93-97. doi: 10.1016/S0140-6736(99)05190-9 PMID: 10675165
13. Hayward AC, Harling R, Wetten S, Johnson AM, Munro S, Smedley J, et al. Effectiveness of an influenza vaccine program for care home staff to prevent death, morbidity, and health service use among residents: Cluster randomised controlled trial. Brit Med J 2006; 333: 1241. doi: 10.1136/bmj.39010. 581354.55 PMID: 17142257
14. Lemaitre M, Meret T, Rothan-Tondeur M, Belmin J, Lejonc JL, Luquel L, et al. Effect of influenza vaccination of nursing home staff on mortality of residents: A cluster-randomized trial. J Am Geriat Soc 2009; 57: 1580-1586. doi: 10.1111/j.1532-5415.2009.02402.x PMID: 19682118
15. Ahmed F, Lindley MC, Alred N, Weinbaum CM, Grohskopf L. Effect of influenza vaccination of healthcare personnel on morbidity and mortality among patients: Systematic review and grading of evidence. Clin Infect Dis 2014; 58: 50-57. doi: 10.1093/cid/cit580 PMID: 24046301
16. Thomas RE, Jefferson T, Lasserson TJ. Influenza vaccination for healthcare workers who work with the elderly. Cochrane Database Sys Rev. 2010 CD005187.
17. Thomas RE, Jefferson T, Lasserson TJ. Influenza vaccination for healthcare workers who care for people aged 60 or older living in long-term care institutions. Cochrane Database Sys Rev. 2013 CD005187.
18. Thomas RE, Jefferson T, Lasserson TJ. Influenza vaccination for healthcare workers who care for people aged 60 or older living in long-term care institutions. Cochrane Database Sys Rev. 2016 CD005187.
19. GRADE working group, Grading of Recommendations, Assessment, Development and Evaluation (GRADE). Available: , http://www.gradeworkinggroup.org.
20. Thomas RE. Is influenza-like illness a useful concept and an appropriate test of influenza vaccine effectiveness? Vaccine 2014; 32: 2143-49. doi: 10.1016/j.vaccine.2014.02.059 PMID: 24582634
21. Osterholm MT, Kelley NS, Sommer A, Belongia EA. Efficacy and effectiveness of influenza vaccines: A systematic review and meta-analysis. Lancet Infect. Dis 2012; 12: 36-44. doi: 10.1016/S1473-3099 (11)70295-X PMID: 22032844
22. Van Buynder PG, Konrad S, Van Buynder JL, Brodkin E, Krajden M, Ramler G, et al. The comparative effectiveness of adjuvanted and unadjuvanted trivalent inactivated influenza vaccine (TIV) in the elderly. Vaccine 2013; 31: 6122-6128. doi: 10.1016/j.vaccine.2013.07.059 PMID: 23933368
23. Simonsen L, Taylor RJ, Viboud C, Miller MA, Jackson LA. Mortality benefits of influenza vaccination in elderly people: An ongoing controversy. Lancet Infect Dis. 2007; 7: 658-666. doi: 10.1016/S1473-3099 (07)70236-0 PMID: 17897608
24. Jhung MA, D'Mello T, Pérez A, Aragon D, Bennett NM, Cooper T, et al. Hospital-onset influenza hospitalizations United States, 2010-2011. Am J Infect Control 2014; 42: 7-11. doi: 10.1016/j.ajic.2013. 06.018 PMID: 24183534
25. Taylor G, Mitchell R, McGeer A, Frenette C, Suh KN, Wong A, et al. Healthcare-associated influenza in Canadian hospitals from 2006 to 2012. Infect Control Hosp Epidemiol 2014; 35: 169-175. doi: 10.1086/674858 PMID: 24442080
26. Régis C, Escuret V, Barret B, Luxemburger C, Pires-Cronenberger S, Gorain C et al. Influenza like illness syndromes in an acute care geriatric unit in Edouard Herriot Hospital, Lyon, France during 5 seasons. 20th European Congress of Clinical Microbiology and Infectious Diseases, Vienna, Austria, 10-13 April 2010. Abstract P1221. Available: Http://www.blackwellpublishing.com/eccmid20/abstract.asp? id=84320
27. Régis C, Gorain C, Pires-Cronenberger S, Crozet MN, Moalla M, Najioullah F et al. La grippe nosocomiale chez les adultes à l'hoa pital Edouard Herriot, Lyon (France), hivers 2004-2005, 2005-2006 et 2006-2007/Nosocomial influenza at Edouard Herriot University Hospital, Lyons (France) winters 2004-2005, 2005-2006 and 2006-2007. Bull Epidémiol Hebd 2008; 34: 308-311. Available: Http://www.invs.sante.fr/beh/2008/34/#5.
28. Cheng VC, Tai JW, Wong LM, Chan JF, Li IW, To KK, et al. Prevention of nosocomial transmission of swine-origin pandemic influenza virus A/H1N1 by infection control bundle. J Hosp Infect 2010; 74: 271-277. doi: 10.1016/j.jhin.2009.09.009 PMID: 20061056
29. Health Protection Agency. HPA national influenza season summary. 2005/2006 season. March 2006. Available: Http://webarchive.nationalarchives.gov.uk/20060323120000/http://www.hpa.org.uk/infections/topics-az/influenza/seasonal/activity0506/flureport.htm
30. Health Protection Agency. HPA national influenza season summary. 2004/2005 season. May 2005. Available: Http://webarchive.nationalarchives.gov.uk/20140714084352/http://www.hpa.org.uk/infections/topics-az/influenza/seasonal/activity0405/text/summary.pdf
31. Elliot AJ, Fleming DM. Surveillance of influenza-like illness in England and Wales during 1966-2006. Euro Surveill. 2006; 11(10): Pii = 651. Available: Http://www.eurosurveillance.org/ViewArticle.aspx? ArticleId=651
32. Paget WJ, Meerhoff TJ, Meijer A; EISS. Epidemiological and virological assessment of influenza activity in Europe during the 2003-2004 season. Euro Surveill 2005; 10: 107-11. PMID: 15879646
33. American Health Care association. The state long-term health care sector: Characteristics, utilization and government funding: 2011 update, 6 September 2011; http://www.ahcancal.org/research-data/trends-statistics/Documents/ST-rpt-STStats2011-20110906-FINAL-web.pdf
34. United States Centers for Disease Control and Prevention. Estimating seasonal influenza-associated deaths in the United States: CDC study confirms variability of flu, 18 March 2015; http://www.cdc.gov/flu/about/disease/us-flu-related-deaths.htm
35. American Hospital Association. AHA Hospital Statistics 2014. Health Forum LLC
36. United States Department of Health and Human Services, The Great Pandemic, the United States in 1918-1919; http://www.flu.gov/pandemic/history/1918/the-pandemic
37. Influenza Vaccination Coverage Among Health-Care PersonnelUnited States, 2010-11 Influenza Season. Morb Mortal Wkly Rep. 2011; 60: 1073-1077
38. Public Health Toronto. Toronto 2015 Influenza Update, November 13, 2015. Available: Http://www. toronto.ca/legdocs/mmis/2015/hl/bgrd/backgroundfile-85948.pdf
39. Influenza coverage for BC health care facilities: Influenza immunization coverage among acute care hospital staff, 2014-15. Available: Http://www.bccdc.ca/resource-gallery/Documents/Statistics%20and %20Research/Statistics%20and%20Reports/Immunization/Coverage/Acute-HCWs-2014-15- influenza-vaccination-coverage.pdf:
40. Ohmit SE, Petrie JG, Malosh RE, Cowling BJ, Thompson MJ, Shay DK et al. Influenza vaccine effectiveness in the community and the household. Clin Infect Dis 2013; 56: 1363-1369. doi: 10.1093/cid/cit060 PMID: 23413420
41. Cowling BJ, Feng S, Finelli L, Steffens A, Fowlkes A. Assessment of influenza vaccine effectiveness in a sentinel surveillance network 2010-13, United States. Vaccine 2016; 34: 61-6. doi: 10.1016/j. vaccine.2015.11.016 PMID: 26611200
42. Skowronski DM, Janjua NZ, De Serres G, Winter Al, Dickson JA, Gardy JL, et al. A sentinel platform to evaluate influenza vaccine effectiveness and new variant circulation, Canada 2010-2011 season. Clin Infect Dis 2012; 55: 332-342. doi: 10.1093/cid/cis431 PMID: 22539661
43. Reed C, Chaves SS, Daily Kirley P, Emerson R, Aragon D, Hancock EB, et al. Estimating influenza disease burden from population-based surveillance data in the United States. PLoS One. 2015; 10: E0118369. doi: 10.1371/journal.pone.0118369 PMID: 25738736
44. Madhi SA, Cutland CL, Kuwanda L, Weinberg A, Hugo A, Jones S et al. Influenza vaccination of pregnant women and protection of their infants. N Engl J Med 2014; 371: 918-931. doi: 10.1056/NEJMoa1401480 PMID: 25184864
45. Madhi SA, Maskew M, Koen A, Kuwanda L, Besselaar TG, Naidoo D et al Trivalent inactivated influenza vaccine in African adults infected with human immunodeficient virus: Double blind, randomized clinical trial of Efficacy, immunogenicity, and safety. Clin Infect Dis 2011; 52: 128-37. doi: 10.1093/cid/ciq004 PMID: 21148531
46. De Villiers PJ, Steele AD, Hiemstra LA, Rappaport R, Dunning AJ, Gruber WC et al. Efficacy and safety of a live attenuated influenza vaccine in adults 60 years of age and older. Vaccine 2009; 28: 228-234. doi: 10.1016/j.vaccine.2009.09.092 PMID: 19796721
47. Jain VK, Rivera L, Zaman K, Espos RA, Sirivichayakul C, Quiambao BP et al. Vaccine for prevention of mild and moderate-to-severe influenza in children. N Engl J Med 2013; 369: 2481-91. doi: 10.1056/NEJMoa1215817 PMID: 24328444
48. van den Dool C, Bonten MJ, Hak E, Wallinga J. Modeling the effects of influenza vaccination of health care workers in hospital departments. Vaccine 2009; 27: 6261-6267. doi: 10.1016/j.vaccine.2009.07. 104 PMID: 19686690
49. van den Dool C, Bonten MJ, Hak E, Heijne JC, Wallinga J. The effects of influenza vaccination of health care workers in nursing homes: Insights from a mathematical model. PLoS Med. 2008; 5: E200. doi: 10. 1371/journal.pmed.0050200 PMID: 18959470
50. Elder AG, O'Donnell B, McCruden EAB, Symington IS, Carman WF. Incidence and recall of influenza in a cohort of Glasgow healthcare workers during the 1993-4 epidemic: Results of serum testing and questionnaire. Brit Med J 1996; 313: 1241-1242. PMID: 8939114
51. Vanhems P Voirin N, Roche S Escuret V, Regis C, Gorain C et al. Risk of influenza-like illness in an acute health care setting during community influenza epidemics in 2004-2005, 2005-2006, and 2006- 2007 Arch Intern Med. 2011; 171: 151-157. doi: 10.1001/archinternmed.2010.500 PMID: 21263105
52. Bénet T, Régis C, Voirin N, Robert O, Lina B, Cronenberger S, et al. Influenza vaccination of healthcare workers in acute-care hospitals: A case-control study of its effect on hospital-acquired influenza among patients. BMC Infectious Diseases 2012; 12: 30. Available: Http://www.biomedcentral.com/1471-2334/12/30 doi: 10.1186/1471-2334-12-30 PMID: 22292886
53. Pebody RG, Andrews N, McMenamin J, Durnall H, Ellis J, Thompson CI, et al. 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. Euro Surveill. 2013; 18(5): Pii = 20389. Available: Http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20389
54. McLean HQ, Thompson MG, Sundaram ME, Kieke BA, Gaglani M, Murthy K, et al. Influenza vaccine effectiveness in the United States during 2012-2013: Variable protection by age and virus type. J Infect Dis 2015; 211: 1529-1540. doi: 10.1093/infdis/jiu647 PMID: 25406334
55. Andrews N, McMenamin J, Durnall H, Ellis J, Lackenby A, Robertson C, et al. Effectiveness of trivalent seasonal influenza vaccine in preventing laboratory-confirmed influenza in primary care in the United Kingdom: 2012/13 end of season results. Euro Surveill 2014; 19(27): Pii = 20851. Available: Http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20851
56. Flannery B, Clippard J, Zimmerman RK, Nowalk MP, Jackson ML, Jackson LA, et al. Early estimates of seasonal influenza vaccine effectivenessUnited States, January 2015.Morb Mortal Wkly Rep. 2015; 64: 10-15.
57. Valenciano M, Kissling E, Reuss A, Valenciano M, Reuss A, Larrauri A, et al. Vaccine effectiveness in preventing laboratory-confirmed influenza in primary care patients in a season of co-circulation of influenza A(H1N1)pdm09, B and drifted A(H3N2), I-MOVE Multicentre Case-Control Study, Europe 2014/15. Euro Surveill. 2016; 21(7): Pii = 30139.
58. Pebody R, Warburton F, Ellis J, Andrews N, Thompson C, von Wissmann B, et al. Low effectiveness of seasonal influenza vaccine in preventing laboratory-confirmed influenza in primary care in the United Kingdom: 2014/15 mid-season results. Euro Surveill. 2015; 20(5): Pii: 21025 Available: Http://www. eurosurveillance.org/ViewArticle.aspx?ArticleId=21025
59. Skowronski DM, Chambers C, Sabaiduc S, De Serres G, Winter AL, Dickson JA, et al. A perfect storm: Impact of genomic variation and serial vaccination on low influenza vaccine effectiveness during the 2014-15 season. Clin Infect Dis 2016; 63: 21-32. doi: 10.1093/cid/ciw176 PMID: 27025838
60. Belongia EA, Simpson MD, King JP, Sundaram ME, Kelley NS, Osterholm MT, et al. Variable influenza vaccine effectiveness by type and subtype: Meta-analysis of studies using the test-negative design. a systematic review and meta-analysis of test-negative design studies. Lancet Infect Dis 2016; 16: 942-951. doi: 10.1016/S1473-3099(16)00129-8 PMID: 27061888
61. Thompson WW, Shay DK, Weintraub E, Brammer L, Cox N, Anderson LJ, et al. Mortality associated with influenza and respiratory syncytial virus in the United States. J Am Med Assoc 2003; 289: 179-186.
62. Rothman K, Lash TL, Greenland S. Precision and statistics in epidemiologic studies. In: Rothman K, Lash TL, Greenland S, editors. Modern Epidemiology, 3rd Edition. Philadelphia: Lippincott Williams & Wilkins; 2008. pp. 148-67.
63. Jackson LA, Jackson ML, Nelson JC, Neuzil KM, Weiss, NS. Evidence of bias in estimates of influenza vaccine effectiveness in seniors. Int J Epidemiol 2006; 35: 337-344. doi: 10.1093/ije/dyi274 PMID: 16368725
64. Riphagen-Dalhuisen J, Burgerhof JG, Frijstein G, van der Geest-Blankert AD, Danhof-Pont MB, de Jager HJ, et al. Hospital-based cluster randomised controlled trial to assess effects of a multi-faceted programme on influenza vaccine coverage among hospital healthcare workers and nosocomial influenza in the Netherlands, 2009 to 2011. Euro Surveill 2013; 18(26): 20512. Available http://www. eurosurveillance.org/ViewArticle.aspx?ArticleId=20512 PMID: 23827527
65. Oshitani H, Saito R, Seki N, Tanabe N, Yamazaki O, Hayashi S, et al. Influenza vaccination levels and influenza-like illness in long-term-care facilities for elderly people in Niigata, Japan, during an influenza A (H3N2) epidemic. Infect Control Hosp Epidemiol 2000; 21: 728-730. doi: 10.1086/501725 PMID: 11089658
66. Enserink R, Meijer A, Dijkstra F, van Benthem B, van der Steen JT, Haenen A, et al. Absence of influenza A(H1N1) during seasonal and pandemic seasons in a sentinel nursing home surveillance network in the Netherlands. J Am Geriatr Soc 2011; 59: 2301-2305. doi: 10.1111/j.1532-5415.2011.03715.x PMID: 22091963
67. Wendelboe AM, Avery C, Andrade B, Baumbach J, Landen MG. Importance of employee vaccination against influenza in preventing cases in long-term care facilities. Infect Control Hosp Epidemiol 2011; 32: 990-997. doi: 10.1086/661916 PMID: 21931249
68. Thompson MG, Naleway A, Fry AM, Ball S, Spencer SM, Reynolds S, et al. Effects of repeated annual inactivated influenza vaccination among healthcare personnel on serum hemagglutination inhibition antibody response to A/Perth/16/2009 (H3N2)-like virus during 2010-11. Vaccine 2016; 34: 981-88. doi: 10.1016/j.vaccine.2015.10.119 PMID: 26813801
69. Ohmit SE, Petrie JG, Malosh RE, Fry AM, Thompson MG, Monto AS. Influenza vaccine effectiveness in households with children during the 2012-13 season: Assessments of prior vaccination and serologic susceptibility. J Infect Dis 2015; 211: 1519-1528. doi: 10.1093/infdis/jiu650 PMID: 25416812
70. Ohmit SE, Thompson MG, Petrie JG, Thaker SN, Jackson ML, Belongia EA, et al. Influenza vaccine effectiveness in the 2011-2012 season: Protection against each circulating virus and the effect of prior vaccination on estimates. Clin Infect Dis 2014; 58: 319-327. doi: 10.1093/cid/cit736 PMID: 24235265
71. McLean HQ, Thompson MG, Sundaram ME, Meece JK, McClure DL, Friedrich TC, et al. Impact of repeated vaccination on vaccine effectiveness against influenza A(H3N2) and B during 8 seasons. Clin. Infect. Dis. 2014; 59: 1375-1385. doi: 10.1093/cid/ciu680 PMID: 25270645
72. Valenciano M, Kissling E, Reuss A, Rizzo C, Gherasim A, Horváth JK, et al. Vaccine effectiveness in preventing laboratory-confirmed influenza in primary care patients in a season of co-circulation of influenza A(H1N1)pdm09, B and drifted A(H3N2), I-MOVE multicentre case-control study, Europe 2014/15. Euro Surveill 2016; 21: Pii: 30139. Available: Http://www.eurosurveillance.org/ViewArticle.aspx? ArticleId=21385
73. Carrat F, Lavenu A, Cauchemez S, Deleger S. Repeated influenza vaccination of healthy children and adults: Borrow now, pay later? Epidemiol Infect 2006; 134: 63-70. doi: 10.1017/S0950268805005479 PMID: 16409652
74. Bodewes R, Kreijtz JHC, Rimmelzwaan GF. Yearly influenza vaccinations: A double-edged sword? Lancet Infect. Dis. 2009; 9: 784-788. doi: 10.1016/S1473-3099(09)70263-4 PMID: 19879807
75. Bodewes R, Fraaij PL, Kreijtz JH, Hillaire ML, Vogelzang-van Trierum SE, Nieuwkoop NJ, et al. Annual influenza vaccination affects the development of heterosubtypic immunity. Vaccine 2012; 30: 7407-7410. doi: 10.1016/j.vaccine.2012.04.086 PMID: 22643217
76. Skowronski DM, De Serres G, Crowcroft NS, Janjua NZ, Boulianne N, Hottes TS, et al. Association between the 2008-09 seasonal influenza vaccine and pandemic H1N1 illness during spring-summer 2009: Four observational studies from Canada. PLoS Medicine 2010; 7: E1000258
77. Skowronski DM, Hamelin ME, De Serres G, Janjua NZ, Li G, Sabaiduc S, et al. Randomized controlled ferret study to assess the direct impact of 2008-09 trivalent inactivated influenza vaccine on A(H1N1) pdm09 disease risk. PLoS ONE 2014; 9: E86555. doi: 10.1371/journal.pone.0086555 PMID: 24475142
78. Kuster SP, Coleman BL, Raboud J, McNeil S, De Serres G, Gubbay J, et al. Risk factors for influenza among health care workers during 2009 pandemic, Toronto, Ontario, Canada. Emerg Infect Dis.2013; 19: 606-615. doi: 10.3201/eid1904.111812 PMID: 23631831
79. Turnberg W, Daniell W, Duchin J. Influenza vaccination and sick leave practices and perceptions reported by health care workers in ambulatory care settings. Am J Infect Control 2010; 38: 486-488. doi: 10.1016/j.ajic.2009.12.006 PMID: 20176412
80. Coleman BL, Boggild AK, Drews SJ, Li Y, Low DE, McGeer AJ. Respiratory illnesses in Canadian health care workers: A pilot study of influenza vaccine and oseltamivir prophylaxis during the 2007/2008 influenza season. Influenza Other Resp Viruses 2011; 5: 404-408.
81. Ridgway JP, Bartlett AH, Garcia-Houchins S, Cariño S, Enriquez A, Marrs R, et al. Influenza among afebrile and vaccinated healthcare workers. Clin Infect Dis. 2015; 60: 1591-1595. doi: 10.1093/cid/civ163 PMID: 25733370
82. De Serres G, Skowronski DM, Patrick DM. Has the emperor got clothes: Scientific evidence and compulsory health care worker influenza immunization. Can Med Assoc J; 2012. Available: Http://www. cmaj.ca/content/early/2012/10/29/cmaj.121679.full/reply#cmaj-el-713530