Influenza (the Flu)

Flu symptoms vary from person-to-person. Some people may only get mildly ill, while others very sick. Flu symptoms appear 1 to 4 days after exposure to the virus.

Classic flu symptoms include the sudden onset of:

• fever
• cough
• muscle aches and pains

Other common symptoms include:

• headache
• chills
• loss of appetite
• fatigue (tiredness)
• sore throat
• runny or stuffy nose

Children may also experience:

• nausea and vomiting
• diarrhea

Additional symptoms to watch for in children include:

• not drinking or eating as much as usual
• not waking up or interacting with others
• not wanting to play or be held (irritable)

Most people recover from the flu in 7 to 10 days with just supportive management.

Everyone is at risk of catching the flu.

Possible complications of the flu include:

• pneumonia and respiratory failure
• secondary bacterial infections
• worsening of chronic health conditions

Other severe outcomes of the flu:

• hospitalization
• death

The people at greatest risk of flu-related complications are:

• adults and children with the following chronic health conditions:
  • heart disease (e.g., congenital heart disease)
  • lung disorders (e.g., asthma, emphysema)
  • diabetes and other metabolic diseases
  • cancer or conditions resulting in a weakened immune system (due to the disease, therapy, or both)
  • kidney disease
  • anemia or blood disorders
  • nervous system disorders or neurodevelopmental conditions
  • morbid obesity
  • children 6 months to 18 years of age undergoing treatment for long periods with acetylsalicylic acid (because of the potential increase of Reye’s syndrome associated with the flu)
• people of any age who are residents of nursing homes and other chronic care facilities
• adults 65 years of age and older
• all children 6 to 59 months of age
• all individuals who are pregnant or up to 2 weeks following delivery
• Indigenous peoples

If you are a person at high risk of flu-related complications and develop symptoms, contact a health care provider. If you need immediate medical attention, call 911 and tell them your symptoms.

The flu and common cold often present very similar, but the former can be more serious, and lead to complications like pneumonia (serious infection of the lungs). Visit the Ministry of Health’s Flu vs. common cold chart (external link) to help determine if you have a cold or the flu.

The flu and COVID-19 are caused by different viruses. They are both very contagious and have similar symptoms. This can make it hard to tell the difference between the flu and COVID-19 (external link) when symptoms appear. You can only confirm if you have the flu or COVID-19 with a test (e.g., a swab).

If you have symptoms of the flu and have not received a negative COVID-19 test, follow COVID-19 prevention measures (external link) to help keep others safe.

The flu is usually diagnosed by your health care provider through one or more of:

• symptoms
• laboratory tests (nasopharyngeal swab)

Most flu symptoms can be managed with:

• rest
• fluids, like water
• over the counter medications to reduce any fever or muscle aches

Speak to your family doctor, nurse practitioner or pharmacist about over-the-counter medications.

In some cases, a health care provider may prescribe specific antiviral medications, especially if you are:

• at high risk of flu-related complications
• very sick with severe symptoms

Contact your family doctor if flu symptoms persist or worsen, or call Health Connect Ontario (formerly TeleHealth) by calling 811 to speak with a nurse.

The flu shot is a vaccine designed to protect against strains of the flu virus that are expected to be circulating during the upcoming flu season. The vaccine stimulates your body’s immune system to fight off infection if you come into contact with the flu virus.

The flu shot is your best defense against the flu. The flu shot is recommended for almost everyone who is 6 months of age or older.

The flu shot protects you if you later get exposed to the virus by helping to:

• prevent you from getting very sick from flu-related complications;
• protect people close to you because, once vaccinated, you are less likely to spread the virus to others;
• reduce the overall burden on the health care system during respiratory virus season; and
• reduce your chances of being infected with the flu and other respiratory viruses at the same time, including COVID-19, which could lead to serious complications.

The flu shot will not protect you against other infections, such as COVID-19 or RSV, so it is also important to be up to date with recommended COVID-19 and RSV immunizations.

A new flu vaccine is produced every year to protect you, your family, and your loved ones during the upcoming flu season. It is important that you get a new flu shot every year because:

• Flu viruses can change over time; the annual shot includes the strains expected to circulate in the upcoming season based on close monitoring of viruses.
• The effectiveness of the flu shot can decrease over time, so receiving a flu vaccine each year helps to keep you protected.

Children from 6 months to less than 9 years of age who have never had a flu shot before should receive 2 doses. It is recommended that the interval between doses be at least 4 weeks apart during the current flu season.

The flu season typically runs from late fall to early spring. The flu shot takes approximately 2 weeks to take full effect. Get your flu shot as soon as the vaccine is available for you.

Talk to your health care provider or pharmacy to learn more.

Getting your flu shot is the most effective way to protect yourself and your loved ones against the flu and flu-related complications. If you get the flu, the flu shot may reduce the severity of the illness and the chances of developing flu-related complications.

The effectiveness of the vaccine can vary and may depend on:

• the health and age of the person getting the flu shot; and
• how well the vaccine matches with the circulating flu strains in that season

 The strains circulating in the population can sometimes change during the time it takes to produce a vaccine. When this happens, the flu shot may not work as well as expected.

 The flu shot protects against 3 or 4 different strains of the flu virus each season. The flu shot can still provide protection even when there is a less-than-ideal match between the vaccine and a circulating strain. This can result in lower effectiveness against one strain of the virus, but will still protect you.

The influenza vaccine is safe. It is much safer to get the vaccine than influenza. Many people who receive the flu shot have no side effects. For those that do, side effects are usually mild and last a few days.

Common local vaccine side effects may include:

• redness
• swelling
• soreness

More general symptoms can include:

• chills
• fatigue
• joint pain
• headache
• mild fever
• muscle aches

Children may also be more fussy than usual after vaccination. Talk to a health care provider about how to help manage common side effects.

When should I seek medical attention?

There is a small chance of a serious allergic reaction to a vaccine called anaphylaxis. It usually happens shortly after a person receives the vaccine and is treatable.

Your health care provider will ask you to stay at the clinic for at least 15 minutes after vaccination. This is so they can watch for abnormal or very rare reactions and treat them promptly. Vaccination sites should have a supply of epinephrine to use in case you have an allergic reaction.

Signs and symptoms of anaphylaxis may include:

• itchy rash
• swelling of the:
  • lips
  • face
  • airway
  • tongue
• increased heart rate
• loss of consciousness
• sudden low blood pressure
• abdominal pain, nausea, vomiting and diarrhea
• sneezing, coughing and difficulty breathing

If you experience any of these symptoms at the vaccination site, report it to your health care provider.

Call emergency services right away if you have left the vaccination site and develop any serious symptoms that could be an allergic reaction.

The National Advisory Committee on Immunization (NACI) (external link) recommends that flu vaccine should be offered annually to anyone 6 months of age and older who does not have a contraindication to the vaccine. It is especially recommended for the following groups:

People at high risk of flu-related complications or hospitalization

• people 6 months of age and older with the following chronic health conditions:
  • heart disease (e.g., congenital heart disease)
  • lung disorders (e.g., asthma, emphysema)
  • diabetes and other metabolic diseases
  • cancer or conditions resulting in a weakened immune system (due to the disease, therapy, or both)
  • kidney disease
  • anemia or blood disorders
  • nervous system disorders or neurodevelopmental conditions
  • morbid obesity
  • children 6 months to 18 years of age undergoing treatment for long periods with acetylsalicylic acid (because of the potential increase of Reye’s syndrome associated with the flu)
• people of any age who are residents of nursing homes and other chronic care facilities
• adults 65 years of age and older
• all children 6 months to 4 years of age
• all individuals who are pregnant
• people in or from First Nations, Métis or Inuit communities
• people of racialized and other equity deserving communities

People capable of transmitting the flu to those at high risk

• care providers in the community
• household contacts (adult and children) of people at high risk of flu-related complications
• people who provide care to children 4 years of age and under
• members of a household expecting a newborn during the flu season
• those who provide services within closed or relatively closed settings to people at high risk (e.g., crew on a cruise ship)

People who provide essential community services

Includes all those working or volunteering in these roles. 

Health care workers and first responders

• first responders
• primary care
• hospital and long-term care home staff

People with significant exposure to birds or mammals

People who are likely to have significant exposure to influenza A (H1N1):

• poultry, livestock, slaughterhouse and processing plant workers
• wildlife officers/researchers
• veterinarians

• Anyone who has had a serious allergic reaction (anaphylaxis) to a previous dose of influenza vaccine and/or to any ingredient in the vaccine, except for egg, should not be vaccinated. People with egg-allergies can safely receive any age-appropriate flu shot.
• Anyone who has developed Guillain-Barré Syndrome (GBS) within six weeks of a previous influenza vaccination should generally not be vaccinated, however this should be weighed against the risks of not being vaccinated against influenza.
• Anyone with a severe acute illness at the time of immunization should wait until the symptoms subside before being immunized. Immunization should not be delayed because of minor acute illness, with or without fever.
• Anyone less than 6 months of age.

Consult with your Health Care Provider to determine if the flu vaccine is right for you.

To get your free flu shot:

• visit a doctor or nurse practitioner
• visit a participating pharmacy*

*Children between the ages of 6 months and 2 years of age must visit a doctor or nurse practitioner. Looking for a family doctor? Visit our Halton Physicians Accepting New Patients webpage.

Find the closest participating pharmacy in:

• Burlington (external link)
• Halton Hills (external link)
• Milton (external link)
• Oakville (external link)

Keep a record of your flu vaccination

• After you get your immunization, you will be given a written record. Add this information to your immunization record.
• If you received the vaccine at a pharmacy, share this information with your regular health care provider. 
• If you develop respiratory symptoms over the next few months, this information will be an important part of your care plan.

People 6 months of age or older can get their flu shot at the same time, or at any time before or after other vaccines, including the COVID-19 and respiratory syncytial virus (RSV) vaccines or RSV monoclonal antibody products. Speak to your health care provider if you have any questions.

For the 2024-2025 season, if you are 65 and older, 3 different flu shots are available:

• The standard-dose vaccine that protects against 4 strains of flu virus.
• The adjuvanted vaccine that protects against 3 strains of flu virus and contains an adjuvant (a substance added to a vaccine that helps the recipient develop an improved immune response).
• The high-dose vaccine, that protects against 4 strains of flu virus, but in higher doses.

All 3 flu vaccine types are safe, effective and offer strong protection to seniors. Talk to your doctor, nurse practitioner or pharmacist about which option is best for you. Do not delay vaccination to wait for a particular product.

FluMist® Quadrivalent (a nasal spray influenza vaccine) is not available through the publicly funded flu program but may be available for purchase. Please contact your health care provider to determine if this vaccine product is appropriate for you or your family.