TLDR: Most healthy travelers do not require booster doses.
Yellow fever is a viral disease transmitted by mosquitoes, primarily in tropical regions. For decades, travelers have relied on the yellow fever vaccine to protect themselves from this potentially life-threatening illness. Following review of the evidence starting in 2014 there have been significant changes in recommendations from WHO (World Health Organization), CDC (Centre for Disease Control), IHR (International Health Regulations) and Canadian Immunization Guidelines.
Yellow Fever Vaccination History
Yellow fever has long been a concern for travelers, with traditional vaccination protocols requiring booster shots every 10 years. This approach was based on the assumption that immunity wanes over time. According to WHO of 600 million doses of the vaccine given since vaccination programs began in the 1930s, only 12 cases of post-vaccination yellow fever cases have been identified. All of the “vaccine failure” cases occurred within 5 years of vaccination, which suggests that immunity does not wane over time.
Up to Date Recommendations
According to WHO, “The yellow fever ‘booster’ vaccination given ten years after the initial vaccination is not necessary. An article published in WER (WHO’s Weekly Epidemiological Record) reveals that the Organization’s SAGE (Strategic Advisory Group of Experts) on immunization has reviewed the latest evidence and concluded that a single dose of vaccination is sufficient to confer life-long immunity against yellow fever disease.”
Dr Helen Rees, past chair of SAGE had this to say “Looking at really very good evidence, it was quite clear to SAGE that in fact a single dose of yellow fever vaccine is effective. This is extremely important for countries where yellow fever is endemic, because it will allow them to reconsider their vaccine scheduling. It is also important for travelers.”
Booster Recommended
The Committee to Advise on Tropical Medicine and Travel (CATMAT) recommends
One-time booster dose for certain cases where:
1. Response to vaccination may have been diminished
| Pregnant Women | Immunosuppressive Medications |
| Immunocompromising Illness | Stem Cell Transplant |
2. Previous dose might not have provided long-term protection
| Fractional Dosing | Undocumented Dose |
| Non-Accredited Admin |
3. High risk of exposure
| YF Outbreaks | YF epidemics |
| Prolonged travel to country with YF transmission |
Booster recommended every 10 years:
| Laboratory personnel working with YF Virus | HIV + individuals |
CATMAT doesn’t currently provide specific recommendations for a booster dose in children who received the yellow fever vaccine before the age of 1 year. Re-immunization for such children traveling to areas with YF transmission risk is based on clinician assessment of risks and benefits.
FAQs About Lifelong Yellow Fever Immunity
Q: Do individuals who have received the “old vaccine” acquire lifelong immunity?
A: Yes, this is a misconception. The Yellow Fever vaccine has not changed in Canada.
Q: Are there any side effects associated with the “new” lifelong vaccine?
A: It is the same vaccine with no additional side effects, they remain the same.
Q: Will countries still require vaccination certificates?
A: The ICVP (International Certificate of Vaccination or Prophylaxis or “yellow card”) will still be required, but only with a single dose of yellow fever vaccination. In 2016 the IHR were amended to indicate a completed ICVP with a single dose of yellow fever vaccine is valid for a lifetime. Countries can’t require proof of revaccination against yellow fever as a condition of entry, even if the last vaccination was greater than 10 years prior.
Conclusion
Understanding the latest recommendations on Yellow Fever could help avoid the hassle and cost associated with obtaining booster shots.
NB: While yellow fever vaccine provides long-lasting protection, it does not eliminate the need for preventive measures against mosquito bites. Mosquito repellents, long-sleeved clothing, and bed nets remain essential in regions where yellow fever is prevalent.