Duration of Protection After Vaccination Against Yellow Fever: A Systematic Review and Meta-Analysis

Area of Science:

• Immunology
• Vaccinology
• Public Health

Background:

• The duration of immunity following a single yellow fever vaccine dose is debated, impacting public health strategies and revaccination recommendations.
• Understanding long-term seroprotection is crucial for managing yellow fever outbreaks and ensuring sustained population immunity.

Approach:

• A systematic literature review and meta-analysis were conducted to synthesize current evidence on yellow fever vaccine efficacy over time.
• Data from 36 studies across 20 countries, involving over 17,000 participants, were analyzed using random-effects models.
• Studies included assessments of protection after one or more vaccine doses, stratified by time since vaccination.

Key Points:

• Healthy adults and children exhibit high seroprotection rates (~100%) by 3 months post-vaccination, sustained for 5-10 years.
• Children vaccinated before age 2 years showed a significantly lower seroprotection rate (52%) within 5 years.
• Immunodeficient individuals demonstrated notable waning of seroprotection, highlighting the influence of immune status.

Conclusions:

• The duration of yellow fever vaccine protection is not uniform and is influenced by host factors such as age and immune competence at the time of vaccination.
• Specific populations, including young children and the immunocompromised, may require different vaccination strategies or booster doses due to faster waning immunity.
• Further research into long-term immunogenicity in diverse populations is warranted to refine yellow fever vaccination guidelines.