Influenza is caused by influenza A and B virus and outbreaks occur every year in Canada, usually during the late autumn and winter months.
Persons at greater risk of serious disease are those with underlying medical conditions(especially heart and lung disease), those with deficiencies in their immune system, and the elderly. Like most countries, Canada has been affected by major pandemics and epidemics of influenza. The unusual occurrence of outbreaks of confirmed and suspected influenza in August and early September in the United States this year, has raised the need for awareness about influenza and the need to maximize opportunities to immunize those who are vaccine-eligible.
The influenza virus vaccine available in Canada is an inactivated vaccine, which is available as a whole-virus or split-virus preparation. The split-virus preparation refers to a vaccine preparation which has been chemically disrupted to reduce the potential for side effects in children. Both whole-cell and split-virus vaccines are similar with respect to their protective effect.
With a good match between the vaccine strain and circulating influenza strain, influenza vaccination has an efficacy of 70% in children and adults. The single most important measure for reducing the impact of influenza is vaccination of people at high risk including the following:
Adults and children with chronic heart or lung disorders.
Residents of nursing homes and chronic care facilities.
Persons 65 years of age and over.
Adults and children with chronic conditions such as diabetes, cancer and immunodeficiency.
Children and adolescents on long term salicylate.
Persons who are capable of transmitting influenza to those at risk should also receive annual vaccination including:
Health care personnel.
Household contacts of people at high risk.
Physicians, nurses and other health care personnel are urged to provide opportunities to vaccinate outpatients and inpatients who are at high risk and who are being discharged from hospital in the fall. Health care personnel should also received this vaccine themselves. Adverse events are uncommon.
References:
Canadian Consensus Conference on Influenza. CCDR 1993; 19: 136-146.
National Advisory Committee on Immunization(NACI). Statement on influenza vaccination for the 1993-94 season. CCDR 1993; 19: 65-72.
Bolette C., Louviere H., Foret T., et al. Influenza A outbreaks. Louisiana. August 1993. MMWR 1993; 42: 689-92
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