Can Breastfeeding Transmit Yellow Fever?

A five-week old infant most likely contracted a vaccine strain of yellow fever virus through breastfeeding, according to a case report published in Canadian Medical Association Journal.

“Until recently, avoidance of vaccination of breastfeeding women with yellow fever vaccine had been based on theoretical grounds only,” writes Dr. Susan Kuhn. “We report the probable transmission of vaccine strain of yellow fever virus from a mother to her infant through breastfeeding, ”which supports current recommendations for breastfeeding mothers to avoid the vaccine.
The yellow fever vaccine is a live-virus vaccine that has been used since the 1940s.
When the infant was 10 days old the mother received pre-travel advice and travel vaccinations,including one for yellow fever. Subsequently,they travelled to Venezuela for one week and breastfeeding was continued. The infant did not receive vaccinations.
The previously healthy five-week old infant male presented to the hospital with a two-day history of fever and irritability. The day before his admission, he had been noted to have focal seizures on alternating sides. Testing of the spinal fluid revealed evidence of recent infection with the yellow fever virus. Given that the travellers elected to stay in urban Venezuela where yellow fever is not known to be a risk, the authors concluded that the likely explanation was transmission of the yellow fever vaccine strain through breastfeeding.
The baby showed no sign of insect bites, had not been in contact with sick people,was not exposed to animals in Canada or elsewhere, had no history of herpes infections in family members and had not had any vaccinations prior to his symptoms.
This probable case of yellow fever virus further supports the current recommendations for avoidance of yellow fever vaccination in lactating mothers of infants under nine months of age. While there may be situations in which the mother will have unavoidable and significant risk of yellow fever exposure, the risk to the infant due to maternal vaccination must be weighed against the risk of wild-type virus infection.
The authors conclude that travelling women should adjust their plans to reduce or limit their risk of exposure or postpone their trip entirely until their infant is no longer breastfeeding or is old enough to be vaccinated.

Kim Barnhardt
Canadian Medical Association Journal 

So what is Yellow Fever? 
Yellow fever is a serious viral disease that's usually spread by a type of mosquito known as the Aedes aegypti mosquito. 
Yellow fever can be fatal. About 7 or 8 people out of 100 who get yellow fever die from it.
Typical First Stage symptoms of yellow fever include:
  • headache
  • high temperature
  • nausea and vomiting
  • backache
Second Stage Symptoms
  • a recurrent high temperature
  • abdominal pain
  • a yellow tinge to the skin and whites of the eyes that's caused by liver damage (jaundice)
  • kidney failure
  • bleeding from the mouth, nose, eyes or stomach – you may have blood in your vomit or in your stools (faeces)
Yellow fever is a type of virus known as a flavivirus. It is transmitted through mosquito bites. It can be spread from one host to another, usually between monkeys, or from monkeys to humans, or from person to person. The mosquitoes live and breed in jungle and urban areas.

Yellow Fever Risk Areas
More about that vaccination

The yellow fever vaccination is recommended for:
  • laboratory workers who handle infected material
  • anyone travelling to, or living in, an area or country where yellow fever is a problem 
  • anyone travelling to a country that requires an International Certificate of Vaccination or Prophylaxis (ICVP) against yellow fever for entry 
People who shouldn't have the yellow fever vaccination include:
  • babies under nine months old – babies who are six to nine months old should only be vaccinated if the risk of yellow fever during travel is unavoidable
  • pregnant women – unless the risk of yellow fever is unavoidable
  • women who are breastfeeding – unless the risk of yellow fever is unavoidable
  • people whose immune systems are lowered (immunosuppressed), such as those with HIV and people receiving chemotherapy or radiotherapy
  • people who are allergic to eggs (the vaccine contains small amounts of egg)
  • people who've had a severe allergic reaction to a previous dose of the yellow fever vaccine
  • people who are allergic to any of the ingredients in the vaccine
  • people who have a condition affecting the thymus gland
  • people who are currently severely unwell (e.g. with a high fever) – this is to avoid confusing the diagnosis of your current illness with any side effects from the vaccine
  • yellow fever naive travellers (those who haven't been previously exposed to the vaccine) who are 60 years old or over (unless the risk of yellow fever is unavoidable)

Side effects of the vaccine

After having the yellow fever vaccine, 10-30% of people will have mild side effects, such as:
  • headache
  • muscle pain
  • soreness at the injection site
  • mild fever
Reactions at the injection site usually occur one to five days after being vaccinated, although other side effects may last for up to two weeks.
An allergic reaction to the vaccine occurs in one case out of every 130,000 doses of the vaccine that are given. 

In the UK, Stamaril is the only licensed yellow fever vaccination. A single dose of the yellow fever vaccine will protect you against yellow fever for at least 10 years. It's recommended that you have a booster dose every 10 years if you're still at risk of infection.

The yellow fever vaccination can only be given at designated and registered centres. For a centre to become a designated yellow fever vaccination centre, it must register with the appropriate authority, which in the UK is either:
  • the National Travel Health Network and Centre (NaTHNac)
  • Health Protection Scotland (HPS)

Certificate of proof

Under regulations set out by the World Health Organization (WHO), anyone travelling to a country or area where the Aedes aegypti mosquito is found must have a Certificate of Vaccination or Prophylaxis (ICVP).
If you've been travelling in an ‘at risk’ area during the past month, it might be a good idea to carry your certificate with you. This will help to avoid potential problems with immigration. It's possible for travellers without a valid yellow fever vaccination certificate to be vaccinated and held in isolation for up to 10 days. An ICVP isn't required for entry into the UK.
If you lose your certificate, you may be able to get another one re-issued as long as you have details of the vaccination batch number and the date that you had the vaccination.

Seeking medical advice

Always consult staff at a designated vaccination centre if you're planning to travel to an area where there's a risk of getting yellow fever. If you tell them where you're travelling to, they will be able to advise you about whether you need to be vaccinated against yellow fever and whether you need an ICVP.


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