|Occupational Health and Safety
Hazardous Substances: Influenza
What is Influenza?
Influenza is a viral infection of the respiratory system. Symptoms of influenza include fever, cough, sore throat, muscle ache,
extreme fatigue and headache. Unlike the common cold and most other respiratory viruses commonly called "the flu", influenza virus
infection can result in severe illness, pneumonia and even death. There are two main types of influenza, influenza A and influenza B.
Influenza is more common in the winter months. Up to 25% of health care workers are infected with influenza during the winter
What is the Incubation Period?
An incubation period is the time between the initial contact with an infectious agent and the first appearance of symptoms
associated with the infection. The incubation period of influenza is 1-3 days.
How is Influenza Transmitted?
Influenza is spread from person to person by inhalation of tiny droplets produced when a person infected with influenza coughs,
sneezes, laughs or sings. It can also be spread by contact with infected respiratory secretions through articles such as bedrails,
facial tissue or utensils. The virus can persist in dried mucus for hours. People with influenza are infectious even before they become
sick and many people with influenza do not know they are infected. The duration of virus shedding is usually not more than 5 days
after the onset of symptoms.
What is an Influenza Outbreak?
An influenza outbreak is a cluster of cases occurring within a short period of time in a defined area or group of people. An influenza
outbreak in a facility is suspected when there are two or more cases of influenza-like illness among residents is a seven-day period.
A suspected outbreak should be reported to the local health unit within one working day or sooner.
What is Influenza Vaccine?
Influenza vaccine is prepared from killed influenza virus. It stimulates the formation of immunity (antibodies) against three strains of
influenza virus likely to be circulating that season.
How Effective is the Vaccine?
Among healthy adults, the vaccine is 70-90% effective. Thus, some vaccinated people will still get influenza. The vaccine protects
only against the 3 included strains of influenza virus. Many other viruses circulate during the winter months that may cause flu-like
symptoms (although generally milder than true influenza) and the vaccine will not protect against these viruses. Rarely, a strain of
influenza not contained in the vaccine will circulate and protection from the vaccine will be less effective. After vaccination, the
vaccine takes 10-14 days to develop protective antibodies. Vaccine is less effective among the frail and the elderly.
Certain diseases such as tetanus and the "childhood diseases" eradicate exceptionally well with vaccination. However, a constantly
mutating virus such as influenza does not. Would influenza be out of control if yearly vaccinations had not been implemented? Have
drug companies, hungry for ever-higher profits, driven the influenza vaccination agenda? Would people's natural immune systems
be better able to fight influenza infections if there were not widespread annual vaccination? These are important questions that are
part of the debate around the need for vaccinations for influenza. Consider them and make an informed choice.
When Should Vaccination Take Place?
Influenza vaccine is given in October or November before the influenza season starts. They can continue right through until April,
though they are preferred in the early months. Because the types of circulating influenza viruses change each year, it is necessary
to get the flu shot every year. Protection from the vaccine declines in 4 months or less, for frail, elderly patients.
What Are the Benefits of Vaccination?
Influenza vaccination is effective in reducing the incidence of infection by influenza A and B in 70-90% of healthy adults and children.
It reduces the severity of the illness if infection occurs. In addition, a recent study has shown that immunizing more than 60% of
health care workers against influenza reduces the risk of death among residents by more than 40%.
The vaccination can be given to anyone over 6 months of age. It is recommended for all pregnant women in high risk groups (all
stages) and it is safe for breast feeding mothers and infants.
Who Should Not Take Influenza Vaccine?
Influenza vaccine should not be given to persons who had an anaphylactic or shock-like reaction to a previous dose of influenza
vaccine or with known anaphylactic or shock-like reaction to eggs or any component of the vaccine. Anaphylactic reaction consists of
rapid onset of hives, swelling of the mouth and throat, difficulty breathing and shock. It is life-threatening but rare following
influenza immunization. People with mild allergies to eggs should not suffer effects from the vaccine because only a tiny amount of
egg is found in the vaccine.
What Are the Side Effects of Influenza Vaccination?
Most people will have no side effects from influenza vaccination. Local symptoms such as arm redness and soreness for 1-2 days
after the shot occur in 1/3 of people, but the symptoms are generally mild and short-lasting. Taking plain acetaminophen at the time
of immunization and every 4 hours for a total of 4 doses significantly reduces arm redness and soreness. Vaccine used in the year
2000 found 2% of recipients reporting redness of the eyes and wheezing. After 24-48 hours the side effects disappear. About 10%
of people who get this vaccine report symptoms such as fever, headache, or malaise but, ironically, this figure is the same as for a
placebo. Influenza vaccine cannot cause influenza because it does not contain live virus.
What is Anti-viral Medication?
Anti-viral medication (drugs) are capable of preventing or treating viral infection. Amantadine is currently the only drug licensed in
Canada for the specific prevention of influenza. It works against influenza A (70% effective) but not influenza B. There is no anti-
viral medication licensed in Canada for the prevention of influenza B. If there is an outbreak of influenza, amantadine should be
taken. Peak amantadine levels are reached 4 hours after the first dose so people can go back to work even though they may not
have received a vaccination. Giving amantadine to residents in long term care facilities and to unvaccinated health care workers has
been shown to stop influenza outbreaks within 24-48 hours. Amantadine is often given even to vaccinated workers for added
What are the Side Effects of Anti-viral Medication?
Twenty years of experience with amantadine have helped to guide dosage and reduce the risk of side effects. When they occur,
side effects may include nausea, lack of appetite, nervousness, anxiety, difficulty in concentrating and light-headedness. There have
been anecdotal reports of deaths associated with amantadine but studies in the medical literature have not determined such an
Two other anti-viral drugs have been licensed for treatment only (not prevention) of influenza A and B.
What are the Side Effects of the Two New Types of Flu Treatment Medication?
Two new anti-influenza medications which were approved for use in Canada at the end of 1999 are Relenza (or zanamivir) and
Tamiflu (or oseltamivir). Health Canada has received at least 17 reports of suspected "adverse reactions" involving Relenza,
including a 52-year-old heart patient who died two days after taking Relenza. Health Canada has also received at least 9 reports
about Tamiflu. Seven of these reports were classified as "serious" and included the death of a 58-year-old man with a history of
asthma. While the link between these anti-viral influenza drugs and the reported side effects has not yet been proven, Health
Canada agrees that it raises "a suspicion". On the issue of effectiveness, the CBC television program, Marketplace, aired a show on
November 7, 2000 about the lack of effectiveness of Relenza and Tamiflu.
People with pre-existing asthma or chronic lung disease, such as emphysema were more likely to have more breathing problems
after taking Relenza (which is taken through an inhaler). Glaxo Wellcome, the makers of Relenza, issued a "dear doctor" letter in
July 2000 after it began receiving reports of patients who didn't have any known airway diseases developing breathing problems
after using the drug. The warning alerted doctors that the drug hadn't been proven safe and effective in people with respiratory
disease and that the drug should be stopped if any patient develops difficulty breathing.
- Employers must make vaccinations and medication available for workers at no cost.
- Vaccinations and medications must be voluntary.
- The union must be involved in worker education programs for those who come in contact with patients who may suffer from
contagious diseases such as influenza.
- Workers who suffer influenza contracted at work or who suffer side effects from vaccination or medication, must file workers'
- If workers are sent home, it must be on full salary.
- Employers must not use this as pre-screening for health care workers.
- Employers must not harass, pressure or force any worker to take a flu vaccination.
Thanks to health care unions in BC for successfully taking on the important fight to ensure health care workers are not forced to be
vaccinated and for providing much of the information found in this fact sheet.
Source: CAW Health, Safety & Environment Department