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Preliminary results show influenza vaccine providing substantial protection against infection during early wave

Interim findings show a substantial reduction in the risk of influenza illness for vaccinated people.
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Preliminary findings show the vaccine has cut the risk of influenza illness by about half during this season’s early and ongoing influenza A epidemic. 

“The earlier-than-usual influenza epidemic this season has enabled us to assess vaccine effectiveness earlier than usual,” said Dr. Danuta Skowronski, physician epidemiologist at the BC Centre for Disease Control (BCCDC) and lead of the Canadian Sentinel Practitioner Surveillance Network (SPSN). “We will update our analyses in the new year, but these interim findings show a substantial reduction in the risk of influenza illness for vaccinated people who seek medical care.” 

The early findings come from the SPSN. Headquartered at the BCCDC, the SPSN includes hundreds of primary care providers within the four largest provinces of Canada: Alberta, British Columbia, Ontario and Quebec. For more than a decade, the SPSN has provided mid-season influenza vaccine effectiveness estimates, typically in January or February, based upon specimens and data collected from patients seeking care for flu-like illness. 

“Vaccine protection is especially important for people at higher risk of severe complications and for a health care system that is managing the circulation of multiple respiratory viruses at the same time as we enter the holiday period.” 
In B.C. and across Canada, the majority of influenza cases this season have been due to the H3N2 subtype of influenza A. The H3N2 subtype is often associated with more severe epidemics and with lower vaccine effectiveness than for other kinds of influenza A or B. The SPSN vaccine effectiveness estimate this season is comparable or higher than measured in previous seasons against the H3N2 subtype.

“Vaccination ahead of the epidemic peak provides the most benefit,” said Skowronski. “Although surveillance data suggest we are currently on the downslope of the epidemic curve, the virus will continue to circulate for several weeks, with the possibility of more spread during the holiday period. A secondary wave due to influenza B also sometimes follows later in the season. If you have not yet been vaccinated against influenza, now is the time.” 

“Vaccines are available for everyone six months and older in B.C. and these preliminary findings show how vaccination remains our best defence against respiratory illnesses. By getting vaccinated against influenza, you can help protect our public health system and the young children and elderly people around you,” said Adrian Dix, B.C. Minister of Health.
Take prevention measures during respiratory season: 

  • Get all recommended vaccines including the annual influenza vaccine and COVID-19 boosters. 
  • Stay at home if you feel unwell and stay away from people at higher risk of serious illness if you have symptoms. 
  • Cough and sneeze into a tissue and dispose of it immediately.  If you don’t have a tissue, cough into your elbow.
  • Wear a mask if you have respiratory symptoms or are recovering from a respiratory illness.
  • Clean your hands frequently with soap and water or with hand sanitizer. 
The BC Centre for Disease Control, a part of the Provincial Health Services Authority, provides public health leadership through surveillance, detection, treatment, prevention and consultation services. The Centre provides diagnostic and treatment services for people with diseases of public health importance, and analytical and policy support to all levels of government and health authorities. The BCCDC also provides health promotion and prevention services to reduce the burden of chronic disease, preventable injury and environmental health risks. For more, visit or follow us on Twitter @CDCofBC.

he Provincial Health Services Authority (PHSA) provides specialized health care services and programs to communities across British Columbia, the territories of many distinct First Nations. We are grateful to all the First Nations who have cared for and nurtured this land for all time, including the xʷməθkwəy̓əm (Musqueam), Sḵwx̱wú7mesh Úxwumixw (Squamish), and səlil̓w̓ətaɬ (Tsleil-Waututh) First Nations on whose unceded and ancestral territory our head office is located. We work in partnership with other B.C. health authorities and the provincial government to deliver province-wide solutions that improve the health of British Columbians. For more information, visit or follow us @PHSAofBC


Media Contact:
Heather Amos
Provincial Health Services Authority
PHSA Media line: 778.867.7472




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