Is the yellow fever live attenuated vaccine shed in semen or saliva?

Yellow Fever Live Attenuated Vaccine Shedding in Semen and Saliva

The yellow fever live attenuated vaccine is not known to be shed in semen or saliva, and there is no documented risk of transmission through casual contact or intimate relations. 1, 2

Vaccine Characteristics and Viral Shedding

The yellow fever vaccine is a live attenuated virus preparation made from the 17D yellow fever virus strain, considered one of the safest and most effective live virus vaccines ever developed 1. Key points about viral shedding:

• The vaccine typically causes a low-level viremia in recipients 4-7 days post-vaccination as anti-yellow virus IgM antibodies develop 2
• This viremia typically resolves within a week as the immune response develops 2
• Unlike some other live vaccines, yellow fever vaccine has not been documented to be transmitted from person to person through casual contact, sexual contact, or other means 1, 2

Safety for Close Contacts

The 2024 ASCO guidelines specifically address the safety of yellow fever vaccine for household contacts:

• "Live vaccines for household contact travelers: The use of MMR and yellow fever vaccines is safe." 1
• There are no special precautions needed for close contacts of someone who has received the yellow fever vaccine 2
• This contrasts with other live vaccines that do require precautions:
  • Oral poliovirus vaccine (contraindicated for household contacts of immunocompromised persons) 1
  • Smallpox vaccine (contraindicated due to risk of transmission) 1
  • Rotavirus vaccine (requires handwashing after diaper changes) 1
  • Varicella vaccine (requires avoiding contact with rash) 1

Considerations for Special Populations

While the vaccine itself is not shed in a way that poses risk to contacts, certain populations should avoid receiving the vaccine directly:

• Immunocompromised individuals 1
• Pregnant women (precaution) 1
• Infants under 9 months of age 1
• Adults over 60 years receiving their first dose (precaution) 1
• Persons with autoimmune diseases 2

Clinical Implications

The lack of documented shedding in semen or saliva has important practical implications:

• No special precautions are needed for sexual partners of vaccinated individuals 2
• Household members and close contacts can safely interact with recently vaccinated individuals 1, 2
• Healthcare workers who receive the vaccine do not need to avoid contact with patients 1

Comparison with Other Live Vaccines

This safety profile distinguishes yellow fever vaccine from certain other live vaccines:

Vaccine	Shedding Risk	Precautions Needed
Yellow fever	No documented person-to-person transmission	None [1,2]
Oral polio	Shed in stool	Contraindicated for household contacts of immunocompromised persons [1]
Smallpox	Risk of transmission (~5.4 events per 100,000 vaccinations)	Should not be given to household members of immunocompromised patients [1]
Rotavirus	Shed in stool	Handwashing after diaper changes [1]
Varicella	Potential transmission through rash	Avoid contact if rash develops [1]

The evidence consistently shows that yellow fever vaccine, despite being a live attenuated vaccine, does not pose a transmission risk through semen, saliva, or other routes of casual or intimate contact.