14 Jun 2016
Infants under 9 months of ageThe risk of yellow fever vaccine-associated encephalitis is higher in infants under nine months of age
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The risk of yellow fever (YF) vaccine-associated encephalitis is higher in infants under nine months of age . The risk is inversely proportional to age (highest risk for the youngest infants) [1-3]. During the 1950’s, when there was no age restriction on the use of the YF vaccine, 15 cases of encephalitis were reported in infants. Of the 15 cases, 13 (87%) occurred in infants under four months of age and all were under seven months of age (age was not documented in the remaining two cases) . The vaccine should therefore never be administered to infants under six months of age [1, 2].
Infants aged six to nine months should only be immunised if the risk of YF during travel is unavoidable; expert opinion should be sought in these situations . For this age group, vaccination is usually only recommended during epidemics / outbreaks when the risk of YF virus transmission may be very high [see TravelHealthPro Country Information Pages].
Individual itineraries should be considered on a case by case basis, and if possible, travel should be delayed until the infant is 9 months of age .
When travel is unavoidable, and YF vaccine is not an option, particular care with insect bite avoidance day and night should be recommended.
Very young children (aged less than 2 years) may have suboptimal sero-conversion rates following a single dose of the vaccine and may, therefore, benefit from a single booster dose 10 years after the original dose [1, 4].
- Public Health England,. Yellow fever Ch 35 Immunisation against infectious disease, April 2014
- Plotkin, S.A. Orenstein, W.A and Offit, P.A Yellow fever vaccine, Ch 38 in Vaccines 6th edition, 2013, Elsevier Saunders, pg 947.
- World Health Organization, Vaccines and vaccination against yellow fever WHO Position Paper – June 2013, weekly epidemiological record, 5 July 2013
- SAGE Working Group, Background Paper on Yellow Fever Vaccine 19 March 2013
Guidelines on clinical procedures
- Record keeping and consent
- Medical letter of exemption
- International Certificate of Vaccination or Prophylaxis (ICVP)