Home›Drug Pipeline› Yellow fever booster in Gambian children yields strong antibody rise
Yellow fever booster in Gambian children yields strong antibody riseBooster dose increases yellow fever protection in young children
The Lancet. Infectious diseasesPublished October 12, 2026Study authors: Pley Caitlin, Jeffries David J, Kanteh Ebrima, Strandmark Julia, Baldeh Aru Kumba, Leigh Mam Nabou, …PubMed ↗NCT05332197 ↗DOI ↗Editorial oversight: Dr. Julia Lee, PhD · Oncology, Genomics & Drug Development
AI-generated summary of the cited source, checked by automated accuracy review.
How we work
Share
Key Takeaway
A 17D booster in Gambian children gave 99% seropositivity and antibody rises up to 7.7-fold, with no vaccine-related serious events.
A phase 3, non-randomised trial in The Gambia assessed a yellow fever 17D booster dose in 610 healthy children aged 1-9 years who had received primary vaccination at 9-12 months. The study was conducted at a single health centre.
After 28 days, 581 of 589 children tested were seropositive, giving 99% seropositivity (97-99% CI). Neutralising antibody responses rose across all age groups, with the largest increase in the oldest children.
On plaque reduction neutralisation testing, the 6-9 year cohort showed a 7.72-fold rise (95% CI 6.27-9.16, p=0.0001). The 4-5 year cohort showed a 6.13-fold rise (95% CI 5.08-7.19, p=0.044), and the 1-3 year cohort a 4.62-fold rise (95% CI 3.89-5.35).
Two severe adverse events occurred, but neither was related to the study vaccine. Other adverse events, discontinuations, and tolerability were not reported. The single-site design limits generalisability.
Funded by the Wellcome Trust, the findings could help policy makers decide whether and when to give yellow fever booster doses to children in endemic areas.
How this fits prior evidence
How this fits prior evidence: This study addresses a gap in clinical data regarding booster efficacy in pediatric populations. While previous coverage noted that environmental and social factors influence arbovirus proliferation and that yellow fever virus has a 30.7% molecular prevalence in non-human primates, this trial provides specific clinical evidence on the 17D vaccine booster's ability to induce neutralising antibodies in children.
Protecting children from yellow fever is a major priority in areas where the virus is common. A study in The Gambia looked at how a booster dose of the 17D vaccine affects children between the ages of 1 and 9. These children had already received their first vaccine as infants.
The results showed that the booster was highly effective. Out of 589 children who received the booster, 581 were seropositive, meaning they developed the necessary antibodies to fight the virus. The study also found that the boost in antibodies was significant across all age groups, though the increase was highest in the oldest children (6 to 9 years old) and lowest in the youngest group (1 to 3 years old).
While the results are promising for health policy, it is important to note that this was a single-site study. While two serious health events occurred during the study, they were not related to the vaccine. These findings can help officials decide on the best timing for booster shots to keep children safe in regions where yellow fever is a threat.
What this means for you:
A booster dose significantly increased protective antibodies against yellow fever in children aged 1 to 9.
Common questions
How effective was the booster dose for children?
The booster was very effective. Out of 589 children who received the booster, 581 were seropositive. This means the vast majority of children developed the necessary antibodies to help fight the yellow fever virus after receiving the extra dose.
Did the booster work differently for different ages?
Yes, the increase in antibodies varied by age. Children aged 6 to 9 saw a 7.72 fold increase, children aged 4 to 5 saw a 6.13 fold increase, and the youngest children aged 1 to 3 saw a 4.62 fold increase in antibodies.
Was the booster dose safe for the children?
The study reported two serious adverse events, but neither was related to the vaccine. Because this was a single-site study, more data may be needed to fully understand the long-term safety and impact for all children.
BACKGROUND: Yellow fever is a vaccine-preventable viral haemorrhagic fever. Vaccine-induced neutralising antibody in children can wane faster than previously thought. This clinical trial investigated the safety and immunogenicity of a yellow fever booster in children of different ages.
METHODS: This open-label, non-randomised, single-site, phase 3 vaccine trial conducted at a health centre in The Gambia enrolled healthy children into three cohorts defined by age. The oldest cohort was aged 6-9 years, the middle cohort was aged 4-5 years, and the youngest cohort was aged 1-3 years. Children were eligible if they had received a primary yellow fever vaccine at age 9-12 months and had no history of a serious adverse event to the yellow fever vaccine or immunodeficiency. All children received a yellow fever 17D booster dose. The primary outcome of neutralising antibody responses to the booster was analysed after 28 days using a linear mixed model in children with complete immunology data and who received their primary vaccine in the 9-12-month period. Safety was a coprimary outcome in all participants. There were no missing data. This trial was registered with ClinicalTrials.gov (NCT05332197) and it is complete and closed to new participants.
FINDINGS: The trial enrolled 610 children (175 in the oldest cohort, 198 in the middle cohort, and 237 in the youngest cohort) between Sept 6, 2022, and Sept 20, 2023. Median age at booster vaccination was 7·2 years (IQR 6·4-9·7) for the oldest cohort, 4·0 years (3·9-5·2) for the middle cohort, and 2·3 years (1·9-3·4) for the youngest cohort. There was a roughly equal sex split in all three cohorts. Immunology analysis was based on 589 children. Baseline PRNT seropositivity occurred in 106 (65% [95% CI 65-72]) of 164 children in the oldest cohort, 130 (67% [60-73]) of 195 children in the middle cohort, and 189 (82% [77-87]) of 230 children in the youngest cohort. 581 (99% [97-99]) of 589 total children were seropositive post-booster. The oldest and middle cohorts had a greater fold change in neutralising antibody on PRNT (7·72 [95% CI 6·27-9·16], p=0·0001 for the oldest cohort; and 6·13 [5·08-7·19], p=0·044 for the middle cohort) compared with the youngest cohort (4·62 [3·89-5·35]). There were two severe adverse events; neither were related to the study vaccine.
INTERPRETATION: Yellow fever booster vaccination was safe and immunogenic in healthy Gambian children. Protective neutralising antibody waned following primary vaccination and boosting had a more pronounced effect in the oldest and middle cohorts (aged 4-9 years) than in the youngest cohort (aged 1-3 years). These data could be of value to policy makers to inform need and optimal timing of yellow fever booster vaccination in children in endemic areas.
FUNDING: Wellcome Trust.
