How The Flu Vaccine Works
Development of the seasonal flu vaccine actually begins many months ahead of flu season. The viruses used in the vaccine are based on extensive research and surveillance into which strains will be most common during the upcoming season.
Seasonal flu vaccines protect against two types of influenza viruses: influenza A and influenza B. They can also be either trivalent or quadrivalent.
The trivalent vaccine protects against three flu viruses: two influenza A viruses and an influenza B virus.
The quadrivalent vaccine protects against the same three viruses as the trivalent vaccine, but it also includes an additional influenza B virus.
Who Should Get An Influenza Vaccine
- Everyone 6 months of age and older should get a yearly influenza vaccination with rare exception.
- Vaccination is especially important for people who are at high risk of serious illness from influenza and those able to transmit or spread influenza to those at high risk.
- Influenza vaccination is free for everyone six months and older in BC for the 2021-2022 influenza season.
- In BC, influenza vaccines are usually available in October. For your best protection, get immunized as soon as possible.
- The influenza vaccine is your best defense against influenza.
- There are two main types of influenza vaccines, the inactivated influenza vaccine, and the live attenuated influenza vaccine.
- Several different types of inactivated influenza vaccines and one type of live attenuated influenza vaccine are available in BC.
- The vaccines protect against either 3 strains of influenza or 4 strains of influenza .
- Your health care provider can tell you which vaccine is recommended for you.
Should My Child Get A Flu Shot
Yes. All children over 6 months old should get a flu shot each year.
Babies and children 6 months to 9 years of age who have never had a flu shot will need 2 doses of the vaccine, given at least 4 weeks apart.
Those who have had one or more doses of the regular seasonal flu shot in the past, or children 9 years of age and older, will only need 1 dose per year.
The vaccine is especially important for children and youth who are at high risk of complications from the flu, including those who:
- are between 6 months and 5 years of age.
- have chronic heart or lung disorders serious enough to need regular medical follow-up.
- have chronic conditions that weaken the immune system, such as immune deficiencies, cancer, HIV or a treatment that causes immune suppression.
- have diabetes or other metabolic diseases.
- have chronic kidney disease.
- have to take acetylsalicylic acid on a daily basis.
- live in a chronic care facility.
- live in First Nation or Inuit communities.
- live with another child or adult who is at risk of complications from the flu.
Children under 5 years old are at higher risk of complications from the flu such as high fever, convulsions and pneumonia. If you have children younger than 5 years old or who have health complications, everyone living in the house should get a flu shot. This is especially important if you have children under 6 months old or if a member of your household is pregnant.
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Treatment And Postexposure Chemoprophylaxis In Pregnant Women
Pregnant women are at high risk of serious complications of influenza infection such as intensive care unit admission, preterm delivery, and maternal death. Patients with flu-like illness should be treated with antiviral medications presumptively regardless of vaccination status. Treatment with oseltamivir is preferred however, if oseltamivir is unavailable, zanamivir may be substituted. Health care providers should not rely on test results to initiate treatment and should treat patients presumptively based on clinical evaluation 38.
Because of the high potential for morbidity, the CDC and ACOG recommend that postexposure antiviral chemoprophylaxis be considered for pregnant women and women who are up to 2 weeks postpartum who have had close contact with someone likely to have been infected with influenza. If oseltamivir is unavailable, zanamivir can be substituted, two inhalations once daily for 10 days. All women who are pregnant or are in the first 2 weeks postpartum should be counseled to call for evaluation immediately if the early signs and symptoms of influenza infection develop 38. For more information about treatment and dosage see ACOG and the Society for MaternalFetal Medicines Seasonal Influenza Assessment and Treatment of Pregnant Women with Influenza-like Illness algorithm at www.acog.org/More-Info/FluVaccine.
Administering Flu Vaccine During The Covid

Curbside and drive-through vaccination clinics may provide the best option for staff and patient safety during the COVID-19 pandemic in communities with high transmission. Read CDCs guidance on drive-through vaccination clinics.
No. Flu vaccination should be deferred for people with suspected or confirmed COVID-19, whether or not they have symptoms, until they have met the criteria to discontinue their isolation. While mild illness is not a contraindication to flu vaccination, vaccination visits for these people should be postponed to avoid exposing healthcare personnel and other patients to the virus that causes COVID-19. When scheduling or confirming appointments for flu vaccination, patients should be instructed to notify the health care professionals office or clinic in advance if they currently have or develop any symptoms of COVID-19.
Flu vaccination should be deferred until a patient is no longer acutely ill. This may be different for patients who are already being cared for in a medical setting than it is for patients who are isolating at home. In a medical setting, the timing for vaccination is a matter of clinical discretion. In general, patients who are isolating at home should wait until they meet criteria for leaving isolation to come to a vaccination setting in order to avoid spreading COVID-19 to others. CDC has guidance for when people can be around others after having COVID-19.
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Flu Vaccine For People With Long
The flu vaccine is offered free on the NHS to anyone with a serious long-term health condition, including:
- a learning disability
- problems with your spleen, for example, sickle cell disease, or if you have had your spleen removed
- a weakened immune system as the result of conditions such as HIV and AIDS, or taking medicines such as steroid tablets or chemotherapy
Talk to your doctor if you have a long-term condition that is not in one of these groups. They should offer you the flu vaccine if they think you’re at risk of serious problems if you get flu.
Reaction At The Injection Site
The most common side effect of the flu shot is a reaction at the injection site, which is typically on the upper arm. After the shot is given, you may have soreness, redness, warmth, and in some cases, slight swelling. These effects usually last less than two days.
To help reduce discomfort, try taking some ibuprofen before getting your shot.
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Can Severe Problems Occur
Life-threatening allergic reactions to flu shots are very rare. Signs of serious allergic reaction can include breathing problems, hoarseness or wheezing, hives, paleness, weakness, a fast heartbeat, or dizziness. If they do occur, it is usually within a few minutes to a few hours after receiving the shot. These reactions can occur among persons who are allergic to something that is in the vaccine, such as egg protein or other ingredients. While severe reactions are uncommon, you should let your doctor, nurse, clinic, or pharmacist know if you have a history of allergy or severe reaction to influenza vaccine or any part of flu vaccine.
There is a small possibility that flu vaccine could be associated with Guillain-Barré syndrome, generally no more than 1 or 2 cases per million people vaccinated. This is much lower than the risk of severe complications from flu, which can be prevented by flu vaccine.
Are Any Of The Available Flu Vaccines Recommended Over Others
Yes, for some people. For the 2022-2023 flu season, there are three flu vaccines that are preferentially recommended for people 65 years and older. These are Fluzone High-DoseQuadrivalent vaccine, Flublok Quadrivalent recombinantflu vaccine or Fluad Quadrivalent adjuvanted flu vaccine. On June 22, 2022, CDCs Advisory Committee on Immunization Practices voted unanimously to preferentially recommend these vaccines overstandard-dose unadjuvanted flu vaccines. This recommendation was based on a review of available studies which suggests that, in this age group, these vaccines are potentially more effective than standard dose unadjuvanted flu vaccines. There is no preferential recommendation for people younger than 65 years.
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How Safe Is The Flu Vaccine
The influenza vaccine is very safe. It cannot cause the flu. Side effects are usually mild and can include:
- mild soreness where the needle went into the arm for 1 to 2 days.
- a mild fever or aches for the first day or 2 after immunization.
Do not give your child ibuprofen or acetaminophen before or around the time of vaccination as it does not prevent the pain of injection and it could have an impact on how well the vaccine works. These medications can be used to treat fever, pain, or other bothersome side effects if they develop after vaccination.
What Kinds Of Flu Vaccines Are Available
CDC recommends use of any licensed, age-appropriate influenza vaccine during the 2021-2022 influenza season. Available influenza vaccines include quadrivalent inactivated influenza vaccine , recombinant influenza vaccine , or live attenuated influenza vaccine . No preference is expressed for any influenza vaccine over another.
Quadrivalent flu vaccines include:
Are any of the available flu vaccines recommended over others?
Yes, for some people. For the 2022-2023 flu season, there are three flu vaccines that are preferentially recommended for people 65 years and older. These are Fluzone High-DoseQuadrivalent vaccine, Flublok Quadrivalent recombinantflu vaccine or Fluad Quadrivalent adjuvanted flu vaccine. On June 22, 2022, CDCs Advisory Committee on Immunization Practices voted unanimously to preferentially recommend these vaccines overstandard-dose unadjuvanted flu vaccines. This recommendation was based on a review of available studies which suggests that, in this age group, these vaccines are potentially more effective than standard dose unadjuvanted flu vaccines. There is no preferential recommendation for people younger than 65 years.
What if a preferentially recommended flu vaccine is not available?
If one of the three preferentially recommended flu vaccines for people 65 and older is not available at the time of administration, people in this age group should get an age-appropriate standard-dose flu vaccine instead.
Who Should Vaccinate?
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Should I Get My Child Vaccinated
Yes, a flu vaccine offers the best defense against getting the flu and spreading it to others. Children younger than 5 years of age especially those younger than 2 years old are at high risk of serious flu-related symptoms and complications.
Flu vaccination has been found to reduce deaths in children. A study in Pediatrics was the first of its kind to show that influenza vaccination is effective in preventing influenza-associated deaths among children.
Nationally, a total of 199 pediatric deaths had been reported to CDC during the 2019-2020 season.
How Does The Flu Spread

Person to Person
People with flu can spread it to others up to about 6 feet away. Most experts think that flu viruses are spread mainly by droplets made when people with flu cough, sneeze, or talk. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs. Less often, a person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth or nose.
To avoid this, people should stay away from sick people and stay home if sick. It is also important to wash hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub if hands are not visibly soiled. Linens, eating utensils, and dishes belonging to those who are sick should not be shared without washing thoroughly first. Eating utensils can be washed either in a dishwasher or by hand with water and soap and do not need to be cleaned separately. Further, frequently touched surfaces should be cleaned and disinfected at home, work and school, especially if someone is ill.
The Flu is Contagious
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Can I Get Seasonal Flu Even Though I Got A Flu Vaccine This Year
Yes. Its possible to get sick with flu even if you have been vaccinated . This is possible for the following reasons:
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You may be exposed to a flu virus shortly before getting vaccinated or during the period that it takes the body to gain protection after getting vaccinated. This exposure may result in you becoming ill with flu before the vaccine begins to protect you.
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You may be exposed to a flu virus that is not included in the seasonal flu vaccine. There are many different flu viruses that circulate every year. A flu vaccine is made to protect against the three or four flu viruses that research suggests will be most common.
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Unfortunately, some people can become infected with a flu virus a flu vaccine is designed to protect against, despite getting vaccinated. The protection provided by the flu vaccination can vary widely, based in part on the health and age factors of the person getting vaccinated. In general, a flu vaccine works best among healthy younger adults and older children. Some older people and people with certain chronic illnesses may develop less immunity after vaccination. Flu vaccination is not a perfect tool, but it is the best way to protect against flu infection.
Who Is Most At Risk
Complications from the flu can include serious conditions, like pneumonia or heart attacks and, in some cases, death. Flu causes about 12,200 hospitalizations and 3,500 deaths in Canada each year.
Some people are more vulnerable to complications and hospitalization from the flu:
- babies under 6 months old are too young to get the flu shot, but they’ll get some protection if their parent got the flu shot while they were pregnant
- children under 5 years of age, because their immune systems are developing, and their airways are small and more easily blocked
- people 65 years old and older, because their immune systems are weaker and they are more likely to have an underlying condition that increases their risk
- pregnant people, because their immune system, heart and lungs change especially later in pregnancy making them more likely to get seriously ill from the flu
- people with underlying health conditions, such as asthma, heart disease or diabetes
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What Side Effects Can Occur After Getting A Flu Vaccine
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While a flu vaccine cannot give you flu illness, there are different side effects that may be associated with getting a flu shot or a nasal spray flu vaccine. These side effects are mild and short-lasting, especially when compared to symptoms of a bad case of flu.
A flu shot: The viruses in a flu shot are killed , so you cannot get flu from a flu shot. Some minor side effects that may occur are:
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Soreness, redness, and/or swelling where the shot was given
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Headache
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Nausea
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Fatigue
The nasal spray: The viruses in the nasal spray vaccine are weakened and do not cause severe symptoms often associated with influenza illness. In children, side effects from the nasal spray may include:
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Runny nose
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In adults, side effects from the nasal spray vaccine may include:
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Runny nose
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Sore throat
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Cough
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If these problems occur, they begin soon after vaccination and usually are mild and short-lived. A flu shot, like other injections, can occasionally cause fainting. Tell your provider if you feel dizzy or have vision changes or ringing in the ears. As with any medicine, there is a very remote chance of a vaccine causing a severe allergic reaction, other serious injuries, or death.
What Is A Flu Vaccine
Influenza vaccines are vaccines that protect against the four influenza viruses that research indicates will be most common during the upcoming season. Most flu vaccines are flu shots given with a needle, usually in the arm, but there also is a nasal spray flu vaccine.
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Why Do I Need To Get Vaccinated Every Year
You need to get the flu vaccine every year because each year the flu vaccine is made to match the different strains of flu virus likely to be in New Zealand. Occasionally the vaccine strains are the same for more than one year, but it is still recommended that you have the vaccine each year, as the protection provided by the vaccine lessens over time. Read more about vaccination against influenza.
Who Should Not Be Vaccinated
There are some people who should not be vaccinated without first consulting a physician. These include:
- People who have a severe allergy to chicken eggs.
- People who have had a severe reaction to an influenza vaccination in the past.
- People who developed Guillain-Barré syndrome within six weeks of getting a previous influenza vaccine.
- Influenza vaccine is not approved for use in children less than 6 months of age.
- People who have a moderate or severe illness with a fever should wait to get vaccinated until their symptoms lessen.
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Are Any Of The Flu Vaccines Recommended Over The Others
No. For the 2021-2022 flu season, CDC and its Advisory Committee on Immunization Practices recommends annual flu vaccination for everyone aged 6 months and older with any licensed age-appropriate flu vaccine including inactivated influenza vaccine , recombinant influenza vaccine , or live-attenuated influenza vaccine , with no preference given for any one vaccine over another.