Travel, live vaccines, and yellow fever: a clinician summary

1. The core issue

Live-attenuated vaccines carry a risk of vaccine-associated infection in immunosuppressed hosts and are generally contraindicated during significant immunosuppression. For travel, the live vaccines to flag are yellow fever (YF-17D), the oral Ty21a typhoid vaccine, and, less commonly requested, live-attenuated influenza (nasal spray), MMR, varicella and BCG. Most other travel vaccines, including hepatitis A and B, injectable typhoid, rabies, Japanese encephalitis, meningococcal conjugate and the inactivated oral cholera vaccine available in Canada, are non-live and safe to administer. The graded recommendations behind this, and the medicine-specific timing points, are set out on the clinic's vaccinations page.

2. Yellow fever specifics

Yellow fever transmission risk is confined to parts of sub-Saharan Africa and tropical South America. Public health guidance lists immunosuppressive and immunomodulatory therapy, solid organ transplantation, malignancy, primary immunodeficiency and symptomatic HIV among the vaccine's contraindications. A single dose is now taken to confer lifelong immunity for most people, and certificate validity is recorded as the lifetime of the person vaccinated; boosters are no longer routinely required. In Canada the vaccine, and the International Certificate of Vaccination or Prophylaxis, can only be issued at centres designated by the Public Health Agency of Canada.

Two distinct requirement types exist. Some states require proof of vaccination from all arriving travellers; others require it only for travellers arriving from, or having transited, a country with risk of transmission. This is why the full itinerary, including transit points, must be reviewed rather than the final destination alone.

3. The medical exemption pathway

Where the vaccine is contraindicated but a certificate would otherwise be required, a clinician at a designated centre can document a medical contraindication on the certificate. Many states accept a waiver, but acceptance is at the discretion of the destination and is not guaranteed, so it should be confirmed for the specific route, ideally with the relevant embassy or consulate. Counsel patients that the waiver addresses the entry requirement only. For an itinerary that genuinely enters a transmission zone, the unmet protection need is a separate and sometimes decisive consideration, and rethinking the route may be the safer advice.

4. Timing around immunomodulators

Where live vaccination is being contemplated, for example in a patient not yet started on treatment, defined intervals apply before and after immunosuppressive therapy, and the response can be blunted by ongoing treatment. This is specialised travel-medicine territory that interacts with disease control; the practical approach is early referral to a travel medicine or designated yellow fever centre, with the vaccination decision and any hold of therapy coordinated with the treating rheumatologist rather than actioned in isolation.

5. Checking requirements

Direct patients, and check yourself, using current official sources rather than static lists: the Government of Canada destination advice pages (Health tab, pre-travel vaccinations) for each country including transit points; the destination's embassy or consulate for anything unusual; and, for a country-by-country reference, the US CDC Yellow Book requirements by country. Advise a travel-health assessment about six weeks before departure.

6. Designated centres (downtown Toronto)

Designated centres near St. Michael's Hospital are listed below; only designated centres can issue the certificate, including a documented exemption. Confirm current designation directly, as the list changes.

For the complete provincial list, see the Public Health Agency of Canada's Yellow Fever Vaccination Centres in Ontario.

Sources: US Centers for Disease Control and Prevention, yellow fever vaccine information and Yellow Book requirements by country; Canadian Immunization Guide, yellow fever vaccine chapter (Public Health Agency of Canada); Government of Canada travel health guidance (travel.gc.ca), accessed July 2026. Centre list from the Public Health Agency of Canada, Yellow Fever Vaccination Centres in Ontario, updated March 2026. Graded vaccination recommendations for rheumatic disease are on the clinic's vaccinations page (CRA 2026; ACR 2022). Educational summary for clinicians; it does not replace a travel medicine assessment.