Does Seasonal Influenza Vaccination Affect the Incidence of pH1N1 Influenza?

2014-08-27 03:18:27 | BioPortfolio


Since the onset of the 2009 pandemic, several observational public health investigations in Canada have identified evidence that suggests that adults, particularly younger adults, who have previously received seasonal influenza vaccine are at increased risk of infection with pH1N1. Investigations in Australia, the United States and the United Kingdom have not identified this effect. While it is not possible to have an answer to whether this effect is real prior to the second wave of the 2009 pandemic, it remains vital to future influenza vaccination programs that the hypothesis that, in 2009, seasonal vaccine increases or decreases the risk of pH1N1 infection be confirmed or refuted.

The objective of this study is to determine whether Ontario adults aged 18-60 years who receive the 2009 seasonal influenza vaccine will be at a 2 fold or greater increased risk of infection with influenza pH1N1 during the second or third wave of the 2009 pandemic.


This study will be an observer -blind randomized controlled trial.

This study will primarily recruit patients from an existing cohort of adult healthcare and other workers in Toronto, as of September 15, 2009, almost 1000 adults are participating in this cohort; with approximately 75 new cohort members being recruited weekly (target is 1300). Recruitment will be supplemented by enrolment at Hamilton Health Sciences Centre (N~3920 employees plus physicians, & midwives), and Queen Elizabeth II Health Centre in Halifax (N~6000 employees plus physicians, & midwives).

Healthcare workers in the Toronto cohort to date have been recruited at the Mount Sinai Hospital, Toronto East General Hospital, and North York General Hospital. Recruitment is just beginning at St. Michael's Hospital, Sunnybrook Health Sciences Centre, and the University Health Network.

Non-healthcare workers are being recruited from several large Toronto employers of primarily office workers. These include the Ontario Agency for Health Protection and Promotion, MaRS and its incubator companies, the head offices of the Ontario Power Generation Corporation, the Art Gallery of Ontario, and the head offices of Scotia Bank. Non-healthcare workers may also be recruited in Hamilton and Halifax if they can be easily identified: they should meet inclusion criteria, and should not work primarily with children, or from a home office.

Participants in the study are completing web-based diaries weekly, and, whenever they develop symptoms possibly compatible with influenza, are submitting nasal swabs, and completing symptom diaries daily while ill. Nasal swabs are tested by PCR on a same day/next day basis, and antivirals are prescribed to staff who develop influenza.

Study Design

Allocation: Randomized, Control: Placebo Control, Endpoint Classification: Efficacy Study, Intervention Model: Single Group Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor), Primary Purpose: Health Services Res




Fluviral influenza vaccine, 2009-2010, Normal saline


North York General Hospital
North York
M2K 1E1


Active, not recruiting


Mount Sinai Hospital, Canada

Results (where available)

View Results


Published on BioPortfolio: 2014-08-27T03:18:27-0400

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Medical and Biotech [MESH] Definitions

Species of the genus INFLUENZAVIRUS B that cause HUMAN INFLUENZA and other diseases primarily in humans. Antigenic variation is less extensive than in type A viruses (INFLUENZA A VIRUS) and consequently there is no basis for distinct subtypes or variants. Epidemics are less likely than with INFLUENZA A VIRUS and there have been no pandemics. Previously only found in humans, Influenza B virus has been isolated from seals which may constitute the animal reservoir from which humans are exposed.

Membrane glycoproteins from influenza viruses which are involved in hemagglutination, virus attachment, and envelope fusion. Fourteen distinct subtypes of HA glycoproteins and nine of NA glycoproteins have been identified from INFLUENZA A VIRUS; no subtypes have been identified for Influenza B or Influenza C viruses.

Infection of domestic and wild fowl and other BIRDS with INFLUENZA A VIRUS. Avian influenza usually does not sicken birds, but can be highly pathogenic and fatal in domestic POULTRY.

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A genus of the family ORTHOMYXOVIRIDAE comprising viruses similar to types A and B but less common, more stable, more homogeneous, and lacking the neuraminidase protein. They have not been associated with epidemics but may cause mild influenza. Influenza C virus is the type species.

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