Dataset Information

A Meta-Analysis of Serological Response Associated with Yellow Fever Vaccination.

ABSTRACT: Despite previous evidence of high level of efficacy, no synthetic metric of yellow fever (YF) vaccine efficacy is currently available. Based on the studies identified in a recent systematic review, we conducted a random-effects meta-analysis of the serological response associated with YF vaccination. Eleven studies conducted between 1965 and 2011 representing 4,868 individual observations were included in the meta-analysis. The pooled estimate of serological response was 97.5% (95% confidence interval [CI] = 82.9-99.7%). There was evidence of between-study heterogeneity (I² = 89.1%), but this heterogeneity did not appear to be related to study size, study design, or seroconversion measurement or definition. Pooled estimates were significantly higher (P < 0.0001) among studies conducted in nonendemic settings (98.9%, 95% CI = 98.2-99.4%) than among those conducted in endemic settings (94.2%, 95% CI = 83.8-98.1%). These results provide background information against which to evaluate the efficacy of fractional doses of YF vaccine that may be used in outbreak situations.

SUBMITTER: Jean K

PROVIDER: S-EPMC5154464 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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A Meta-Analysis of Serological Response Associated with Yellow Fever Vaccination.

Jean Kévin K Donnelly Christl A CA Ferguson Neil M NM Garske Tini T

The American journal of tropical medicine and hygiene 20161010 6

Despite previous evidence of high level of efficacy, no synthetic metric of yellow fever (YF) vaccine efficacy is currently available. Based on the studies identified in a recent systematic review, we conducted a random-effects meta-analysis of the serological response associated with YF vaccination. Eleven studies conducted between 1965 and 2011 representing 4,868 individual observations were included in the meta-analysis. The pooled estimate of serological response was 97.5% (95% confidence in ...[more]

PMID: 27928091

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Project description:BackgroundYellow fever is a vector-borne disease affecting humans and non-human primates in tropical areas of Africa and South America. While eradication is not feasible due to the wildlife reservoir, large scale vaccination activities in Africa during the 1940s to 1960s reduced yellow fever incidence for several decades. However, after a period of low vaccination coverage, yellow fever has resurged in the continent. Since 2006 there has been substantial funding for large preventive mass vaccination campaigns in the most affected countries in Africa to curb the rising burden of disease and control future outbreaks. Contemporary estimates of the yellow fever disease burden are lacking, and the present study aimed to update the previous estimates on the basis of more recent yellow fever occurrence data and improved estimation methods.Methods and findingsGeneralised linear regression models were fitted to a dataset of the locations of yellow fever outbreaks within the last 25 years to estimate the probability of outbreak reports across the endemic zone. Environmental variables and indicators for the surveillance quality in the affected countries were used as covariates. By comparing probabilities of outbreak reports estimated in the regression with the force of infection estimated for a limited set of locations for which serological surveys were available, the detection probability per case and the force of infection were estimated across the endemic zone. The yellow fever burden in Africa was estimated for the year 2013 as 130,000 (95% CI 51,000-380,000) cases with fever and jaundice or haemorrhage including 78,000 (95% CI 19,000-180,000) deaths, taking into account the current level of vaccination coverage. The impact of the recent mass vaccination campaigns was assessed by evaluating the difference between the estimates obtained for the current vaccination coverage and for a hypothetical scenario excluding these vaccination campaigns. Vaccination campaigns were estimated to have reduced the number of cases and deaths by 27% (95% CI 22%-31%) across the region, achieving up to an 82% reduction in countries targeted by these campaigns. A limitation of our study is the high level of uncertainty in our estimates arising from the sparseness of data available from both surveillance and serological surveys.ConclusionsWith the estimation method presented here, spatial estimates of transmission intensity can be combined with vaccination coverage levels to evaluate the impact of past or proposed vaccination campaigns, thereby helping to allocate resources efficiently for yellow fever control. This method has been used by the Global Alliance for Vaccines and Immunization (GAVI Alliance) to estimate the potential impact of future vaccination campaigns.

Project description:IntroductionPrompted by recent amendments of Yellow Fever (YF) vaccination guidelines from boost to single vaccination strategy and the paucity of clinical data to support this adjustment, we used the profile of the YF-specific CD8+ T-cell subset profiles after primary vaccination and neutralizing antibodies as a proxy for potentially longer lasting immunity.Methods and findingsPBMCs and serum were collected in six individuals on days 0, 3, 5, 12, 28 and 180, and in 99 individuals >10 years after YF-vaccination. Phenotypic characteristics of YF- tetramer+ CD8+ T-cells were determined using class I tetramers. Antibody responses were measured using a standardized plaque reduction neutralization test (PRNT). Also, characteristics of YF-tetramer positive CD8+ T-cells were compared between individuals who had received a primary- and a booster vaccination. YF-tetramer+ CD8+ T-cells were detectable on day 12 (median tetramer+ cells as percentage of CD8+ T-cells 0.2%, range 0.07-3.1%). On day 180, these cells were still present (median 0.06%, range 0.02-0.78%). The phenotype of YF-tetramer positive CD8+ T-cells shifted from acute phase effector cells on day 12, to late differentiated or effector memory phenotype (CD45RA-/+CD27-) on day 28. Two subsets of YF-tetramer positive T-cells (CD45RA+CD27- and CD45RA+CD27+) persisted until day 180. Within all phenotypic subsets, the T-bet: Eomes ratio tended to be high on day 28 after vaccination and shifted towards predominant Eomes expression on day 180 (median 6.0 (day 28) vs. 2.2 (day 180) p = 0.0625), suggestive of imprinting compatible with long-lived memory properties. YF-tetramer positive CD8+ T-cells were detectable up to 18 years post vaccination, YF-specific antibodies were detectable up to 40 years after single vaccination. Booster vaccination did not increase titers of YF-specific antibodies (mean 12.5 vs. 13.1, p = 0.583), nor induce frequencies or alter phenotypes of YF-tetramer+ CD8+ T-cells.ConclusionThe presence of a functionally competent YF-specific memory T-cell pool 18 years and sufficient titers of neutralizing antibodies 35-40 years after first vaccination suggest that single vaccination may be sufficient to provide long-term immunity.

Dataset Information

A Meta-Analysis of Serological Response Associated with Yellow Fever Vaccination.

Publications

A Meta-Analysis of Serological Response Associated with Yellow Fever Vaccination.

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