# Influenza (flu) Canonical page: https://carecard.ca/knowledge/immunizations-serology/influenza **Status:** Required for all students **Valid for:** One influenza season — a new dose and new proof are required each year. This page explains why the seasonal flu shot is required and how it works, using guidance from Health Canada and the Public Health Agency of Canada. It is educational and does not replace advice from your own health care provider or the specific rules of your program and placement site. See the [Source & references](#source--references) at the bottom. ## Why this is required [#why-this-is-required] As a medical student on placement you are in close contact with patients who are at high risk of severe influenza — older adults, newborns, pregnant patients and people with chronic conditions. Health Canada considers **annual influenza vaccination an essential component of the standard of care for all health care workers**. * **Protects you.** The flu shot lowers your own risk of getting sick during a busy placement. * **Protects your patients.** Vaccinating health care workers reduces the risk of transmitting influenza to patients at high risk of severe outcomes. * **Keeps you working.** Fewer infections means fewer missed placement days and less strain on the clinical team. Health Canada recommends the seasonal flu vaccine annually for **everyone 6 months of age and older** who has no contraindication, so getting it also protects your own household and community. ## About influenza (the flu) [#about-influenza-the-flu] Influenza is a respiratory infection caused by influenza **A and B** viruses, which cause seasonal epidemics each year. It spreads by aerosols and droplets from coughing or sneezing, and through contact with respiratory secretions. The incubation period is usually about 2 days, and adults can spread it from about a day before symptoms start to roughly 5 days after. * **Symptoms** usually come on suddenly: fever, cough and muscle aches, often with headache, chills, loss of appetite, fatigue and sore throat. * **Complications** can include pneumonia, respiratory failure, cardiovascular complications and worsening of underlying chronic conditions; infection is also linked to a higher risk of heart attack and stroke in the first 15 days. * **Global burden:** the World Health Organization estimates 3 to 5 million cases of severe illness and 290,000 to 650,000 deaths from influenza each year. ## How the vaccine works [#how-the-vaccine-works] Most flu vaccines contain **inactivated (killed) influenza viruses** that cannot cause the flu; they teach your immune system to recognise the strains expected to circulate that season. Protective antibodies develop about **two weeks** after vaccination. Health care workers are advised to receive a **non-live (inactivated) vaccine**; a live nasal-spray vaccine (LAIV) also exists but is generally not used for HCWs. In Canada the seasonal vaccine is trivalent — covering an A(H1N1) strain, an A(H3N2) strain and a B strain — and higher-dose or adjuvanted versions are offered to help protect adults 65 and older. ## How well it works [#how-well-it-works] * Effectiveness varies from season to season, depending on how well the vaccine strains match the viruses actually circulating and on your age and health. * Even in a season with a less-than-ideal match, vaccinated people — especially those at high risk of complications — are still more likely to be protected than people who are unvaccinated. * Getting vaccinated in consecutive seasons does not reduce how well the vaccine works. ## Safety and side effects [#safety-and-side-effects] Reactions are usually **mild and short-lived**: * Soreness at the injection site, typically lasting up to two days * Systemic reactions such as muscle aches, headache, fatigue or malaise Serious adverse events are rare. Guillain-Barré syndrome has been estimated at about **1 excess case per million** doses — lower than the risk of Guillain-Barré from influenza illness itself. People with an egg allergy can safely receive any influenza vaccine, at the full dose and without prior skin testing. ## Staying protected [#staying-protected] Because the circulating strains change and immunity fades within a year, a **new dose is needed every influenza season**. Vaccination **before the season starts (in the fall) is strongly preferred**, though the vaccine can still be given later in the season. The flu shot can be given on the **same day as your COVID-19 vaccine** or any other routine vaccine. Confirm the timing that applies to you with your program or a health care provider. ## What to submit [#what-to-submit] * An official record or receipt for **this season's** influenza vaccine * The vaccine product name and the date it was given * Your full legal name and date of birth ## Accepted proof [#accepted-proof] * Pharmacy immunization receipt * Clinic, public health or provincial immunization record * Occupational or student health record of your flu shot * International immunization record with an English translation ## Good to know [#good-to-know] * Last season's flu shot does not count — proof must be for the **current** influenza season. * Get it early in the fall so your record is ready before your placement start date. * If your site runs on-site flu clinics, keep the receipt they give you. * Declination policies differ — some sites require you to wear a mask for the season if you opt out, so check your program's rules. ## Validity [#validity] Valid for one influenza season. You will need a new dose, and new proof, each year. ## Source & references [#source--references] The medical information on this page is adapted from Health Canada and the Public Health Agency of Canada: * [Health Canada](https://www.canada.ca/en/health-canada.html) * [Influenza vaccines: Canadian Immunization Guide](https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-10-influenza-vaccine.html) * [Flu (influenza): For health professionals](https://www.canada.ca/en/public-health/services/diseases/flu-influenza/health-professionals.html) * [Immunization of workers: Canadian Immunization Guide](https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-3-vaccination-specific-populations/page-11-immunization-workers.html) * [Canadian Immunization Guide](https://www.canada.ca/en/public-health/services/canadian-immunization-guide.html)