Giuseppe
Emeritus
Selection bias explains seasonal vaccine's protection -- Janjua et al. 339: b4972 (BMJ, extracts, edited)
Published 24 November 2009, doi:10.1136/bmj.b4972
Cite this as: BMJ 2009;339:b4972
Letters
Seasonal vaccine and H1N1 - Selection bias explains seasonal vaccine?s protection
The first 150 words of the full text of this article appear below.
Vaccine efficacy is estimated to be around 80% for trivalent inactivated flu vaccine during seasons when the components closely match circulating strains.1 The surface HA/NA proteins included in the 2008-9 vaccine are antigenically very distant from those of the 2009 pandemic A/H1N1 (pH1N1) virus. Few adults given the 2008-9 vaccine developed neutralising antibody against pH1N1,2 but Garcia-Garcia and colleagues report 73% (95% confidence interval 34% to 89%) cross-protection against pH1N1 with it.3 This finding probably stems from a selection bias associated with their second paradoxical finding: participants with chronic conditions were at 80% (55% to 91%) reduced risk of hospitalisation for pH1N1, a result that contradicts known risk factors for severe flu outcomes generally and for pH1N1 specifically.4
In their study, cases and controls emerged from different source populations. Cases more often presented directly requiring hospitalisation (98% v 34%). Controls were more often seen after specialty referral. Hospitalised cases reflect (. . .)
Naveed Z Janjua, epidemiologist
1, Danuta M Skowronski, epidemiologist
1, Travis S Hottes, epidemiologist
1, Gaston De Serres, medical epidemiologist
2, Natasha S Crowcroft, director
3, Laura C Rosella, epidemiologist
1 Influenza and Emerging Respiratory Pathogens, BC Centre for Disease Control, Vancouver, British Columbia, Canada,
2 Institut national de sant? publique du Qu?bec,
3 Surveillance and Epidemiology, Ontario Agency for Health Protection and Promotion Toronto, Ontario, Canada
danuta.skowronski@bccdc.ca
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<cite cite="http://www.bmj.com/cgi/content/extract/339/nov24_3/b4972">Selection bias explains seasonal vaccine's protection -- Janjua et al. 339: b4972 -- BMJ</cite>Cite this as: BMJ 2009;339:b4972
Letters
Seasonal vaccine and H1N1 - Selection bias explains seasonal vaccine?s protection
The first 150 words of the full text of this article appear below.
Vaccine efficacy is estimated to be around 80% for trivalent inactivated flu vaccine during seasons when the components closely match circulating strains.1 The surface HA/NA proteins included in the 2008-9 vaccine are antigenically very distant from those of the 2009 pandemic A/H1N1 (pH1N1) virus. Few adults given the 2008-9 vaccine developed neutralising antibody against pH1N1,2 but Garcia-Garcia and colleagues report 73% (95% confidence interval 34% to 89%) cross-protection against pH1N1 with it.3 This finding probably stems from a selection bias associated with their second paradoxical finding: participants with chronic conditions were at 80% (55% to 91%) reduced risk of hospitalisation for pH1N1, a result that contradicts known risk factors for severe flu outcomes generally and for pH1N1 specifically.4
In their study, cases and controls emerged from different source populations. Cases more often presented directly requiring hospitalisation (98% v 34%). Controls were more often seen after specialty referral. Hospitalised cases reflect (. . .)
Naveed Z Janjua, epidemiologist
1, Danuta M Skowronski, epidemiologist
1, Travis S Hottes, epidemiologist
1, Gaston De Serres, medical epidemiologist
2, Natasha S Crowcroft, director
3, Laura C Rosella, epidemiologist
1 Influenza and Emerging Respiratory Pathogens, BC Centre for Disease Control, Vancouver, British Columbia, Canada,
2 Institut national de sant? publique du Qu?bec,
3 Surveillance and Epidemiology, Ontario Agency for Health Protection and Promotion Toronto, Ontario, Canada
danuta.skowronski@bccdc.ca
-