# Varicella (chickenpox) Canonical page: https://carecard.ca/knowledge/immunizations-serology/varicella **Status:** Required for all students **Valid for:** Does not expire once you have two documented doses or laboratory evidence of immunity. This page explains why proof of varicella immunity is required and how the vaccine 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] Placement sites require proof that you are immune to the vaccine-preventable diseases you could encounter — or pass on — during patient care, and varicella (chickenpox) is one of them. * **Protects you.** Chickenpox is far more serious in adults than in children, and clinical settings are exactly where a susceptible student can be exposed — immunity protects you from severe disease. * **Protects your patients.** The virus is highly contagious and dangerous to newborns, pregnant patients and immunocompromised patients. Documented immunity lowers the risk that you pass it on or become part of an outbreak. * **It is usually already covered.** Most people are immune from childhood chickenpox or routine vaccination, so many students only need to locate their records or confirm immunity with a blood test. Health Canada recommends that **all health care workers be immunized with two doses of varicella vaccine when there is any uncertainty about their immunity.** For someone newly entering the Canadian health care system, a self-reported history of chickenpox is **not** accepted on its own — documented doses or laboratory evidence of immunity is expected, which is why programs often ask for a varicella titre. ## About varicella (chickenpox) [#about-varicella-chickenpox] Varicella is caused by the varicella-zoster virus (VZV) and is highly infectious, with attack rates of **65% to 87%** among susceptible household contacts. It spreads by the **airborne route** and by direct contact with fluid from the skin lesions, and a person is contagious from 1–2 days before the rash appears until every lesion has crusted over. * **Symptoms** include a low-grade fever, mild general symptoms and a generalised, itchy rash with lesions at different stages. * **Complications** can include secondary bacterial skin infections, bacteremia, pneumonia, and encephalitis; chickenpox is much more severe in **adolescents, adults and people with weakened immune systems**, in whom rates of pneumonia, encephalitis and death are higher. * **In pregnancy**, infection can cause congenital varicella syndrome, and maternal chickenpox around the time of birth can cause severe illness in the newborn. * **Later in life**, the virus can reactivate as **herpes zoster (shingles)**. ## How the vaccine works [#how-the-vaccine-works] The varicella vaccine is a **live attenuated vaccine** — it uses a weakened form of the virus to teach your immune system to recognise it without causing disease. It comes as a **univalent** varicella vaccine or combined with measles, mumps and rubella as **MMRV**. Because it is a live vaccine, it is **not given during pregnancy**. ## How well it works [#how-well-it-works] * A single dose is about **94%** effective in children, rising to about **98%** after a second dose. * Ten years after two doses, effectiveness is estimated at **over 98% against any chickenpox** and **100% against severe disease** — which is why two doses are the standard requirement. ## Safety and side effects [#safety-and-side-effects] Reactions are usually **mild**: * Pain, swelling or redness at the injection site (about 10–20%) * A low-grade fever * A mild varicella-like rash in a small number of people, less common after the second dose Serious adverse events are rare, and anaphylaxis is very rare. ## Staying protected [#staying-protected] Two documented doses (or laboratory evidence of immunity) give **long-lasting protection** that does not need routine boosters. If a titre shows you are not immune, your program may ask for one or two varicella doses given a few weeks apart. Because it is a live vaccine, it should not be given during pregnancy, and pregnancy should be avoided for a short period after vaccination — confirm timing with a health care provider. ## What to submit [#what-to-submit] * A record showing **two doses** of a varicella-containing vaccine (varicella or MMRV), **or** * A lab report (titre) showing immunity to varicella * Your full legal name and date of birth on every document ## Accepted proof [#accepted-proof] * Childhood immunization record (e.g. the yellow immunization card) * Provincial or public health immunization record * Lab report of a varicella serology/titre with the result clearly stated * International immunization card with an English translation ## Good to know [#good-to-know] * A self-reported history of chickenpox is often **not enough** for a newly hired health care worker or student — most programs want two documented doses or a titre. * If a titre comes back non-immune, you may need one or two doses; leave time for this before your placement start date. * Varicella is frequently confirmed by blood test rather than records, so check what your site accepts before booking anything. ## Validity [#validity] Does not expire once you have two documented doses or laboratory evidence of immunity. ## 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) * [Varicella (chickenpox) vaccines: Canadian Immunization Guide](https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-24-varicella-chickenpox-vaccine.html) * [Varicella (chickenpox)](https://www.canada.ca/en/public-health/services/immunization/vaccine-preventable-diseases/varicella-chickenpox.html) * [Varicella proof of immunity — 2015 update](https://www.canada.ca/en/public-health/services/publications/healthy-living/varicella-proof-immunity-2015-update.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)