No Observed Risk of Pregnancy and Maternal-Fetal Transmission of Zika Virus Following Blood Transfusion

BACKGROUND: Zika virus (ZIKV) is primarily mosquito-borne, but can also be transfusion- and sexually transmitted. Maternal-fetal transmission may result in fetal loss or severe congenital defects. METHODS: We surveyed blood recipients enrolled in a donor-recipient-linked study of transfusion-transmitted infections to assess potential risk of ZIKV maternal-fetal transmission following transfusion. Participants were tested for antibodies to ZIKV, dengue and chikungunya viruses. Positive serology from post- and pre-transfusion samples and from linked donors were tested using real-time PCR. RESULTS: The mean age of female recipients was 65 years (36-80). Only one was < 50 years. None reported having sexual intercourse within the first month and none became pregnant within six months following transfusion. Male recipients were a mean 62 years of age (31-81). Twenty percent of males had sexual intercourse with a female partner within three months of transfusion; no pregnancies resulted. Females and males most commonly reported that they were no longer sexually active or felt too ill after transfusion. All of the respondents were IgM and RT-PCR negative. CONCLUSIONS: Our survey of blood recipients, combined with derived data and the literature, suggest that most transfused women are beyond the age of likely pregnancy and most transfused women and men are too infirm from the underlying condition to engage in sex. However, 20% of male recipients did report having sexual intercourse during the ZIKV infectious period.

within the first month and none became pregnant within six months following transfusion. Male recipients were a mean 62 years of age (31-81). Twenty percent of males had sexual intercourse with a female partner within three months of transfusion; no pregnancies resulted. Females and males most commonly reported that they were no longer sexually active or felt too ill after transfusion. All of the respondents were IgM and RT-PCR negative. CONCLUSIONS: Our survey of blood recipients, combined with derived data and the literature, suggest that most transfused women are beyond the age of likely pregnancy and most transfused women and men are too infirm from the underlying condition to engage in sex.
However, 20% of male recipients did report having sexual intercourse during the ZIKV infectious period.

Background
Zika virus (ZIKV) is primarily mosquito-borne, but can also be transfusionand sexually transmitted. [1][2][3] Maternal-fetal transmission may result in fetal loss or 4 severe congenital defects. [4][5][6] Transfusion-transmission of ZIKV to a pregnant blood recipient with subsequent vertical transmission and birth defects are the most feared consequences of transfusion-related ZIKV. Following transfusiontransmission of ZIKV, infected men could potentially transmit ZIKV sexually to their pregnant partners. [2][3] The U.S. Food and Drug Administration (FDA) issued guidance in 2016 that required individual donor nucleic acid testing (ID-NAT) of all U.S. blood donors for ZIKV. 7 An FDA revision was issued in 2018 that allows donor nucleic acid testing in mini-pools (MP-NAT) with conversion to ID-NAT if pre-defined thresholds are met (e.g. local or regional ZIKV-positive donor). 8 Both strategies, ID-NAT and MP-NAT, come with considerable cost. [9][10][11][12] We surveyed blood recipients enrolled in a donor-recipient-linked prospective study of transfusion-transmitted infections, performed ZIKV, DENV and CHIKV serologic and RT-PCR testing and collected demographic and clinical laboratory data from the time of transfusion. The main aims of the study were to assess the likelihood of pregnancy or sexual transmission to a pregnant woman following transfusion, and by extension, the likelihood that transfusion-transmitted ZIKV could result in vertical transmission.

Methods
Zika virus exposure and pregnancy risk surveys Blood transfusion recipients were surveyed who enrolled in the donorrecipient-linked prospective study, Transfusion-Related Infections Prospectively Studied (TRIPS; NCT00023023) from the beginning of the ZIKV epidemic period (November 2015) until routine blood donor screening for ZIKV RNA was implemented in the U.S. (December 2016). Surveys were administered by telephone to assess the likelihood of pregnancy among participants transfused during the ZIKV epidemic period and to assess by extension, the risk of ZIKV transmission to a fetus following a ZIKV transfusion-transmitted infection. Recipients were called at least three times, at different times of the day and on separate days over a 4-week period.
Recipients whose phone numbers had changed, or who didn't return our calls were sent a letter requesting they contact us. When all efforts to contact them failed during a 4-week period, they were considered lost to follow-up. All blood recipients who completed the survey provided verbal informed consent after an IRB-approved 5 script was read to them. weeks of enrollment might still be in an incubation period at enrollment and confound the analysis of a subsequent (within study) viremia or antibody seroconversion.
All study participants provided informed consent prior to sample collection.
The study was approved and is reviewed annually by NIH and Johns Hopkins institutional review boards (IRB).

Laboratory Testing
Detailed descriptions of all laboratory testing methodology can be found in

Discussion
The risk of exposure to blood products during pregnancy, and therefore the risk of ZIKV transfusion-transmission to a pregnant woman, appears to be very low.
Murphy et. al. analyzed over forty-five thousand pregnancies in a large tertiary care center and found that only 0.124% of expectant mothers received a transfusion at some point in their pregnancy. 18 A less recent study using U.S. hospital discharge data reported a range of 0.24 to 0.46%. 19 ZIKV is thought to be most efficiently transmitted during the first trimester, and in Murphy's study only 0.04% received a transfusion during this period. 6,18 The results of our blood recipient survey suggest that if a female blood recipient was infected with ZIKV, the likelihood of pregnancy following transfusion, and by extension transmission to a fetus, is very low. The average age of our female blood recipients was 65 years, which is similar to a large study of U.S. blood recipient demographics. 20,21 None of our female respondents had sexual intercourse within 4 weeks of transfusion; ZIKV is typically no longer detectable in blood 14 days after infection. 22 About half had not been sexually active for many years and the other half felt too ill to have sex, or were still in the hospital 4 weeks after transfusion.
Our results also suggest that if a male blood recipient was infected with ZIKV within 3 months of transfusion, the probability of sexual transmission to a female pregnant partner, or sexual intercourse that results in pregnancy is likely low. However it is possible: twenty percent of male recipients reported having sexual intercourse within the Zika virus infectious period; Taken together, the risk of maternal-fetal transmission of ZIKV related to transfusion is likely low and the cost of universal blood donor testing is substantial. In

Conclusion
Although this study is too small to draw broad inferences, the derived data and the literature suggest that many, and probably most, woman who are transfused are beyond the age of likely pregnancy and by extension, of maternalfetal ZIKV transmission and associated birth defects. Further, most transfused women and men are too infirm from the underlying condition that necessitated transfusion to engage in sex during the interval when the ZIKV virus circulates in the blood stream or is most likely to be present in semen. Twenty percent of male recipients did report having sexual intercourse during the ZIKV infectious period.
Though these circumstances make it unlikely that a blood transfusion would secondarily result in a ZIKV-related birth defect, they do not exclude the possibility.

Ethics approval
All study participants provided informed consent prior to sample collection. The study was approved and is reviewed annually by the National Heart Lung and Blood Institute of the National Institutes of Health and the Johns Hopkins Medicine institutional review boards.

Availability of data and materials
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Funding
This research was supported by the National Institutes of Health (NIH) Clinical Center, part of the NIH Intramural Research Program.