Antibody responses to yellow fever vaccine in 9 to 11-month-old Malian and Ghanaian children

ABSTRACT

Background: The World Health Organization recommends use of a single yellow fever (YF) vaccine dose for life and fractional doses in outbreaks when there are limited vaccine stocks. In endemic regions, this vaccine is given as part of routine infant immunization programs around 9 months of age. There is a need to better understand immune responses when vaccinating infants particularly in contexts where the child may be malnourished.

Methods: Data from 393 Malian and Ghanaian infants who concomitantly received measles and YF vaccines at 9 to 11 months of age were retrospectively analyzed. Response to YF vaccine was examined for association with nutritional status at time of vaccination, sex, age, pre-vaccination titers and season of vaccination.

Results: Neutralizing antibodies following vaccination were unaffected by season of vaccination, sex, pre-vaccination titers or nutritional status, though there was a trend to higher titers in males and children with higher height for age z-scores. Seroconversion rates differed significantly between countries (63.5 in Ghana vs. 91.0% in Mali).

Conclusion: Longitudinal, prospective studies are needed to optimize the use of YF vaccine in infants in endemic settings. There may be a need for booster vaccinations and to compare various vaccine preparations to optimize the use of available vaccines.

KEYWORDS:

• Neutralizing antibody
• yellow fever (YF)
• vaccine
• African
• infant

Acknowledgments

The authors acknowledge the study sites, all participants and their communities. We also acknowledge the Serum Institute of India, Meningitis Vaccine Project (MVP), and Program for Appropriate Technology in Health (PATH) for funding the original trials, access to data for this analysis and review of manuscript drafts.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was funded by a Wellcome Trust Institutional Strategic Support Fund to Dr Olubukola Idoko (PS2874_WMNP) and Medical Research Council funding to Prof Beate Kampmann (MC_UP_A900/1122). The Program for Appropriate Technology in Health (PATH) funded the original trials, gave access to data for this analysis and reviewed manuscript drafts.