BC researchers investigate H1N1 risk factors

14 September 2009

Investigators at the BC Centre for Disease Control (BCCDC) are conducting an innovative study to determine which age groups in BC are at greatest risk of contracting the 2009 pandemic H1N1 influenza virus (pH1N1 or Swine flu) and developing severe symptoms as a result. The Michael Smith Foundation for Health Research and the Provincial Health Services Authority are funding this rapid response research to inform decisions about the pH1N1 immunization campaign in BC, which is scheduled to begin in fall 2009.

The research has two objectives:

  • Estimating what proportion of people has antibodies to pH1N1, by age group. Antibodies protect the individual from being infected with the virus.
  • Assessing the strength of the “cell-mediated immune response”, by age group. This is the process by which immune system cells attack virus-infected cells in the patient.

“The risk of severe illness is what’s most important in driving our interventions and prioritization,” says Dr. Danuta Skowronski, Epidemiologist with the BCCDC and co-principal investigator of the study with Virologist Dr. Martin Petric. “The goal of our immunization program is first and foremost to protect those who are most at risk for severe outcomes, such as hospitalization and death. And for that, we need to know not only who is at risk of becoming infected, but who is at risk of severe outcomes and why. We need to look not only at the antibody response, but at other aspects of effective virus clearance once infected.”

Seasonal influenza typically has the most serious impact on the very young and those over 65. Case reports and studies conducted to date have shown that critical illness resulting from pH1N1 infection has hit young adults unusually hard. This may be because older adults and other age groups have some degree of immunity to pH1N1 based on previous exposure. Viruses similar to the currently circulating pH1N1 virus sole-circulated sometime between 1918 and 1957 so that people born during that period are more likely to have some pre-existing protection.

The BCCDC, a PHSA agency, is conducting the study to develop a more detailed understanding of which populations are at greater risk of infection and serious outcomes. The study results will help inform risk mitigation measures such as vaccine use. The aspect of the study looking at the level of antibodies to pH1N1 follows up on research that the agency began in May, just weeks after the virus emerged as a global public health threat. Examining cell-mediated immune response, however, is a novel approach. It involves examining the immune response of cells to pH1N1, based on the responses of cytokines (proteins that help regulate the immune system reaction), and how that process can be controlled.

“Others have looked at antibody responses, but cell-mediated immunity is not generally being examined realtime in response to emerging disease threats by applied public health researchers,” says Skowronski. “I think there’s increased recognition that it’s a very important component, but it’s so intricate to do.” BCCDC researchers will collaborate with Dr. Janet McElhaney of Providence Health Care and the University of British Columbia on this aspect of the research.

Skowronski says BC public health researchers have built up capacity to conduct this type of complex rapid response research. She notes that the study will provide critical information about pH1N1 risks but also more generally inform the immuno-epidemiologic aspects of novel influenza viruses. The researchers have, therefore, an obligation to carry out the research, says Skowronski. “Public health personnel in Canada are busy with planning and preparedness for programs. Not everybody is able to invest the time, energy, expertise and money in conducting necessary research to inform those program and policy decisions. While others are working on aspects that they are capable of doing, we’re capable of doing this, so we should do it.”

She credits MSFHR and PHSA for helping to get the research off the ground so quickly. After pH1N1 emerged in 2009, MSFHR convened a working group – including researchers, the PHSA and the Ministries of Health Services and Healthy Living and Sport – to explore options on how the health research community could respond. The working group identified rapid response pH1N1 research as a priority for BC and MSFHR solicited a proposal from BCCDC to carry it out. The merit of BCCDC’s proposal was confirmed in an expedited peer review process, and received ethical approval.

The study was launched in July, with an initial focus on recruiting volunteers, who have been asked to provide a blood sample. Laboratory analysis began in September. “Our goal is to have results from the study in October so that there can be time for synthesis and understanding of their importance and influence on decision-making,” says Skowronski, a clinical assistant professor at the University of BC School of Population and Public Health.

Other co-investigators on this immuno-epidemiology study are Drs. Janet McElhaney, Dale Purych, Travis Hottes, Naveed Janjua, Mel Krajden, David Patrick, and Robert Brunham.  Also contributing to other aspects of rapid response research at the BCCDC and as part of a multi-disciplinary team to address pH1N1 knowledge gaps are Drs. Jennifer Gardy and Patrick Tang (virus evolution and genomics), Monika Naus (behavioural studies), MSFHR Senior Scholar Babak Pourbohloul (mathematical modeling) and Fawziah Marra (pharmacist’s role).

The BCCDC is recruiting volunteers for the pH1N1 immuno-epidemiology study from five specific age categories: 80-90, 60-64, 49-51, 39-40 and 20-31 years. These age categories were chosen for their likely first childhood exposures to different influenza subtypes. Researchers aim to recruit 50 healthy volunteers in each category. Individuals interested in participating can call TASC Research Services at 604-584-8889 or e-mail tasc@tascresearch.com.