Measles Vaccine Virus RNA in Children More Than 100 Days after Vaccination

Abstract

Measles vaccines have been in use since the 1960s with excellent safety and effectiveness profiles. Limited data are available on detection of measles vaccine virus (MeVV) RNA in human subjects following vaccination. Available evidence suggests MeVV RNA can be identified up to 14 days after vaccination, with detection beyond this rare. In routine diagnostic testing, we used two real-time reverse transcription-polymerase chain reaction (RT-rPCR) assays targeting M and F genes to identify measles virus (MeV) and MeVV RNA. Confirmatory testing was performed with an N gene RT-rPCR, followed by sequence confirmation of RT-rPCR positives by semi-nested conventional RT-PCR assays targeting portions of the N, H, and L genes. We report detection and confirmation of MeVV RNA from the respiratory tract of 11 children between 100 and 800 days after most recent receipt of measles-containing vaccine. These novel findings emphasize the importance of genotyping all MeV detections and highlight the need for further work to assess whether persistent MeVV RNA represents viable virus and if transmission to close contacts can occur.

Keywords: RNA; RT-PCR; measles; measles vaccine; measles virus; measles-mumps-rubella; persistence; vaccine safety; vaccines.

Figure 1

Schematic representation of the measles virus (MeV) genome highlighting the genes (open boxes), proteins produced (yellow arrows) and the diagnostic sequencing PCR assay targets (red boxes). The assays indicated are described in Table S1. The genome is drawn to scale and is based on MeV Edmonston strain (GenBank accession: AF266288). Higher resolution version is located at https://doi.org/10.6084/m9.figshare.8248082.

Figure 2

Phylogenetic analysis of MeV partial nucleoprotein (N)-gene sequences. The sequenced region is the World Health Organization (WHO)-recommended 450-nt nucleoprotein (N) gene fragment encoding the carboxyl-terminal of the gene. WHO MeV reference strain sequences include GenBank accession numbers and by eight clades designated A–H. Clade A MeVV sequences associated with patients (red) are indicated by case number and associated GenBank accession number. Clade A wildtype MeV (blue) indicated by WHO reference strain and GenBank accession number. Phylogenetic analysis was used the neighbour-joining method. Maximum composite likelihood methods was performed in MEGA7 with a bootstrap analysis of 1000 replicates. The percentage of replicate trees in the bootstrap test (1000 replicates) greater than 85 are shown next to the branches. A higher resolution version is located at https://doi.org/10.6084/m9.figshare.7649063.