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Safety Of Some Yellow Fever Vaccine Questioned

Seven severe cases of illness -- including 6 deaths -- after yellow-fever vaccination are described in two articles and one research letter in this week's issue of The Lancet.

Although these reports call into question the safety of yellow-fever vaccination, the overall conclusion to be drawn is that vaccination programs should be continued, with the need for new research to explain how some individuals can become sensitized to yellow-fever vaccine.

Yellow fever is an acute disease caused by a virus transmitted by mosquitoes, and is characterised by high fever, jaundice, kidney failure and low blood pressure.

The virus is common in tropical and subtropical Africa and South America, and vaccination programs have increased over the past 20 years as the disease has spread to urban areas.

Yellow-fever vaccine is regarded as one of the safest virus vaccines, with few side effects or adverse events.

Now, Pedro Vasconcelos and colleagues from WHO Collaborating Centre for Arbovirus Reference and Research, Brazil, report the occurrence of two fatal cases of hemorrhagic fever associated with yellow fever 17DD substrain vaccine in Brazil.

The first case, a 5-year-old white girl, was characterized by sudden onset of fever accompanied by headache, malaise and vomiting 3 days after receiving yellow fever and measles-mumps-rubella vaccines; she later died after a 5-day illness.

The second patient -- a 22-year-old Afro-Caribbean woman -- developed a sore throat and fever, accompanied by headache, myalgia (muscle pain), nausea, and vomiting 4 days after yellow-fever vaccination. She then developed symptoms including jaundice and renal failure, and died after 6 days of illness.

Tissue damage in both patients was typical of wild-type yellow fever. The investigators conclude that although these serious complications of yellow-fever vaccination are extremely rare, the safety of yellow fever 17DD vaccine needs to be reviewed.

In the second report, Michael Martin and colleagues from the U.S. Centers for Disease Control describe the illness and death (in three cases) of four elderly patients shortly after they had been vaccinated against yellow fever.

The clinical presentations were characterized by fever, myalgia, headache, and confusion, followed by severe multisystemic illnesses. The investigators suggest that there may be a possible causal relation between the illnesses and yellow-fever vaccination.

However, they caution that because yellow fever remains an important cause of illness and death in South America and Africa, vaccination should be maintained until the frequency of adverse events to vaccination is quantified.

Raymond Chan and colleagues from the South Western Area Pathology Service, Sydney, Australia, describe in a research letter a man vaccinated with the 17D204 strain of yellow fever virus, who later died of the disease.

Genetic sequencing showed that the virus isolated from the patient was identical to the vaccine strain of the same batch, but differed from wild-type virus. Both viruses contained a mutation, although the association of this mutation with virulence is unknown.

The investigators comment that severe, rapidly progressive and ultimately fatal disease can follow use of the 17D204 vaccine strain, and that there is need for renewed discussion as to the safety of the vaccine and the indications for its use.

In an accompanying Commentary (p 84), Philippe Marianneau and colleagues from Institut Pasteur, Lyons, France, conclude, "...the use of 17D vaccination remains highly advisable for people living in or travelling to endemic and epidemic zones. However, these three reports raise relevant questions about the mechanisms of attenuation of yellow-fever virus that should be urgently investigated."

(Editor's Note: The first issue of a new monthly review journal, The Lancet Infectious Diseases, to be published on August 1, will contain a comprehensive review of yellow fever by Dr. Thomas Monath, a co-author of the paper describing the Brazilian cases. Monath emphasizes that, in the absence of preventive vaccination, yellow fever is a terrifying and untreatable disease that still causes 1,000-fold more illness and death than the feared Ebola virus.)

(Reference: The Lancet, 14th July 2001)

[Contact: Dr. Pedro Vasconcelos, Dr. MS Cetron, Dr. Raymond Chan, Dr. Vincent Deubel, Dr. Thomas P Monath]

13-Jul-2001

 

 

 

 

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