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. 2021 Jun 3;10(6):693.
doi: 10.3390/pathogens10060693.

The Usefulness of a Duplex RT-qPCR during the Recent Yellow Fever Brazilian Epidemic: Surveillance of Vaccine Adverse Events, Epizootics and Vectors

Alice L N Queiroz  1 , Rafael S Barros  1 , Sandro P Silva  1 , Daniela S G Rodrigues  1 , Ana C R Cruz  1 , Flávia B Dos Santos  2 , Pedro F C Vasconcelos  1 , Robert B Tesh  3 , Bruno T D Nunes  1 , Daniele B A Medeiros  1
Affiliations

The Usefulness of a Duplex RT-qPCR during the Recent Yellow Fever Brazilian Epidemic: Surveillance of Vaccine Adverse Events, Epizootics and Vectors

Alice L N Queiroz et al. Pathogens. .

Abstract

From 2016 to 2018, Brazil faced the biggest yellow fever (YF) outbreak in the last 80 years, representing a risk of YF reurbanization, especially in megacities. Along with this challenge, the mass administration of the fractionated YF vaccine dose in a naïve population brought another concern: the possibility to increase YF adverse events associated with viscerotropic (YEL-AVD) or neurological disease (YEL-AND). For this reason, we developed a quantitative real time RT-PCR (RT-qPCR) assay based on a duplex TaqMan protocol to distinguish broad-spectrum infections caused by wild-type yellow fever virus (YFV) strain from adverse events following immunization (AEFI) by 17DD strain during the vaccination campaign used to contain this outbreak. A rapid and more accurate RT-qPCR assay to diagnose YFV was established, being able to detect even different YFV genotypes and geographic strains that circulate in Central and South America. Moreover, after testing around 1400 samples from human cases, non-human primates and mosquitoes, we detected just two YEL-AVD cases, confirmed by sequencing, during the massive vaccination in Brazilian Southeast region, showing lower incidence than AEFI as expected.

Keywords: Brazil; duplex RT-qPCR; vaccine adverse effects; yellow fever.

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Conflict of interest statement

The authors did not have any conflict of interest.

Figures

Figure 1
Figure 1
Comparison of primer performance in singleplex and duplex RT-qPCR formats.
Figure 2
Figure 2
Evaluation of the Duplex RT-qPCR in YFV isolates (n = 28) and YF suspected cases (n = 53) in comparison to methods routinely used for diagnosis (isolation and RT-PCR).
Figure 3
Figure 3
Distribution of confirmed yellow fever human cases (n = 70/319) and NHP (n = 94/512) investigated during the 2016–2017 epidemic in Brazil. Monthly distribution of human (A) and NHP cases (B). Distribution of human cases as well as NHP cases and mosquitoes positive for YFV per state (C).
Figure 4
Figure 4
Distribution of the Ct values of the positive samples used in the article. (A) human samples (B) samples of NHP and mosquitoes and the red circle shows the mean Ct.
Figure 5
Figure 5
Study flowchart to evaluate the usefulness of a Duplex RT-qPCR for the surveillance of vaccine adverse events, epizootics and vectors during the 2016–2017 yellow fever Brazilian epidemic.
See this image and copyright information in PMC

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