Transmission of yellow fever vaccine virus from breast feeding mothers to their infants: reporting of yellow fever virus (YFV) RNA detection in milk specimens

Abstract

Background: Because of yellow fever’s serious impact on health, vaccination is the principal strategy to control the disease. Administration of the yellow fever vaccine to breastfeeding women should be before they complete 9 months post-delivery, in order to prevent transmission of the yellow fever vaccine virus to their infants through breast feeding. This study aimed to confirm whether the excretion of yellow fever vaccine virus is in milk of vaccinated breastfeeding mothers and to confirm the probable transmission to their infants through breast milk. Methods: Samples were taken as follows: one serum specimen was taken 3-14 days after the date of the vaccination, and breast milk specimens were taken at four different time points between 3-4 days apart. Specimens were obtained from eight nursing mothers, who received the YVF vaccine (17DD). Mothers were asymptomatic before and after the vaccine administration but their infants developed symptoms after administration. Maternal serum samples were tested for YFV specific IgM antibodies through immuno-fluorescent assay (IFA). RNA was extracted from serum and breast milk specimens and YFV RNA screened using real-time polymerase chain reaction (RT-PCR). Results: In total, five mothers (62.5%) were positive for YFV and two mothers (25%) had YFV RNA in serum. Among milk specimens, YFV RNA was detected during the four different mentioned collection times as follows (positive milk specimens/total milk specimens): 3/8 (37.5 %), 4/6 (66.6%) and 1/4(25%). RNA was completely undetectable in the last collection time. Conclusions: YFV transmission from mothers to their babies through breast-feeding was highly probable indicated by the temporal relationship to mother’s YF vaccination.

Arthropod-Borne Flaviviruses in Pregnancy

“…An effective live attenuated (17D strain) vaccine is available for YFV and elicits a durable, life-long adaptive immune response [ 159 ]. The vaccine has historically been contraindicated in pregnancy, breastfeeding mothers, and infants under six months of age, as YFV RNA has been detected in breastmilk following vaccination [ 163 ] and there have been several cases of vaccine-associated encephalitis in newborns of recently vaccinated mothers [ 110 , 164 , 165 ]. However, recent studies of pregnant women receiving YFV vaccination have demonstrated no increased risk of fetal adverse events, and thus vaccination should be considered in the setting of severe epidemics or unavoidable travel to high-risk areas given the risk of severe disease in unvaccinated populations [ 166 , 167 , 168 , 169 , 170 , 171 ].…”