Yellow fever Flashcards
What is the case fatality of yellow fever in travellers?
About a quarter will develop the toxic stage of disease and of these about half will die
What is the rate of disease in Africa and South America?
50/100 000 travellers for a 2 week stay during the high risk season in an endemic area in Africa.
5/100 000 travellers for a 2 week stay in South America, but the rate varies on season and location.
What is the risk of YEL-AVD and YEL-AND?
YEL-AVD: 0.3/100 000, x 4 (1.2/100 000) if over 60 and x 13 (4/100 000) if over 70.
YEL-AND: 0.8/100 000 and x 3 (2.2/100 000) if over 60
When is the high risk season in Africa?
End of rainy season and beginning of dry season (usually July to October) in rural West Africa, however may be episodically transmitted even in dry season in both rural and densely populated urban areas - large population of mosquitoes.
When is the high risk season in South America?
Rainy season, January to May, with highest risk Feb-March. However due to the large population of A. aegypti mosquitos in both rural and urban areas, remains at risk for large scale urban epidemics.
Which area of Africa has the highest risk?
West Africa more than Central or East Africa
Why is the risk lower in South America than in Africa? (when urban outbreaks are not occurring)
Because the mosquitoes that transmit the virus in the sylvanic cycle between monkeys do not often come into contact with humans. As well, there is a higher vaccine coverage in the population which increases local immunity
How do you give the vaccine?
0.5mL reconstituted (given within 1 hour of this) for both adults and children, IM or SC
What is the one vaccine that you should try not to give together with yellow fever if possible?
If time allows, give MMR and yellow fever 4 weeks apart (one randomised control study stating that giving on the same day reduces seroconversion to yellow fever, mumps and rubella, but further studies are needed)
What other test can the yellow fever vaccine affect?
Mantoux testing - may be unreliable for at least 4 weeks. Best to do it before (all live vaccines cause this)
What are the four contraindications to yellow fever vaccine?
- Anaphylaxis to eggs or any of the vaccine components, or previous hypersensitivity/anaphylaxis to the vaccine
- Immunocompromised state (including primary or acquired immunodeficiency, malignant neoplasms, transplant, drugs)
- Thymus disorders including thymoma, thymectomy, myaesthenia gravis, DiGeorge syndrome, damage to the thymus from chemotherapy or graft-versus-host disease
- Age less than 9 months
What are the three precautions?
- Pregnancy/breastfeeding
- Age over 60
- HIV
Describe the issue of giving yellow fever vaccine in pregnancy
Counsel women - has been reported to be associated with higher rates of spontaneous abortions, but no trial done to show statistically significant. However, a considerable number of doses to pregnant women have been given without adverse effect. Risk in early pregnancy thought to be very low.
Advise not to travel to yellow fever area.
- if low risk areas of a country (and only for country requirements) - give a waiver
- if risk thought to be high (due to place, activities, season) then WHO says risk of disease outweighs risk of vaccine, so should vaccinate. Note may need to be given another dose later if they continue to be at risk of exposure.
Advise women of childbearing age not to fall pregnant within 28 days.
Describe the issue of giving yellow fever vaccine in breastfeeding
Although rare, there has been case reports of transmission of the virus to exclusively breastfed infants less than 9 months of age via breast milk, resulting in encephalitis (all recovered normally). Better to wait until stops breastfeeding, or until infant is 9 months (then give to mother and infant). Do not give to women breastfeeding infants less than 9 months of age unless high risk of exposure that cannot be avoided - expert advice should be consulted
Describe the issues to consider in giving the vaccine to people over 60
Documented discussion between provider and patient.
Consider age, vaccine status, medical conditions and treatment, itinerary (location, season, duration, activities). If travel is unavoidable and decision is made to vaccinate, inform of risk of adverse events; if decision made not to vaccinate then give waiver and discuss mosquito precautions.
