V-safe Surveillance: Local and Systemic Reactogenicity in Pregnant Persons
Characteristics of Persons Who Identified as Pregnant in the V-safe Surveillance System and Received an mRNA Covid-19 Vaccine. 
Frequency of Local and Systemic Reactions Reported on the Day after mRNA Covid-19 Vaccination in Pregnant Persons.
From December 14, 2020, to February 28, 2021, a total of 35,691 v-safe participants identified as pregnant. Age distributions were similar among the participants who received the Pfizer–BioNTech vaccine and those who received the Moderna vaccine, with the majority of the participants being 25 to 34 years of age (61.9% and 60.6% for each vaccine, respectively) and non-Hispanic White (76.2% and 75.4%, respectively); most participants (85.8% and 87.4%, respectively) reported being pregnant at the time of vaccination (Table 1). Solicited reports of injection-site pain, fatigue, headache, and myalgia were the most frequent local and systemic reactions after either dose for both vaccines (Table 2) and were reported more frequently after dose 2 for both vaccines. Participant-measured temperature at or above 38°C was reported by less than 1% of the participants on day 1 after dose 1 and by 8.0% after dose 2 for both vaccines.
Most Frequent Local and Systemic Reactions Reported in the V-safe Surveillance System on the Day after mRNA Covid-19 Vaccination.
Shown are solicited reactions in pregnant persons and nonpregnant women 16 to 54 years of age who received a messenger RNA (mRNA) coronavirus disease 2019 (Covid-19) vaccine — BNT162b2 (Pfizer–BioNTech) or mRNA-1273 (Moderna) — from December 14, 2020, to February 28, 2021. The percentage of respondents was calculated among those who completed a day 1 survey, with the top events shown of injection-site pain (pain), fatigue or tiredness (fatigue), headache, muscle or body aches (myalgia), chills, and fever or felt feverish (fever).
These patterns of reporting, with respect to both most frequently reported solicited reactions and the higher reporting of reactogenicity after dose 2, were similar to patterns observed among nonpregnant women (Figure 1). Small differences in reporting frequency between pregnant persons and nonpregnant women were observed for specific reactions (injection-site pain was reported more frequently among pregnant persons, and other systemic reactions were reported more frequently among nonpregnant women), but the overall reactogenicity profile was similar. Pregnant persons did not report having severe reactions more frequently than nonpregnant women, except for nausea and vomiting, which were reported slightly more frequently only after dose 2 (Table S3).
V-safe Pregnancy Registry: Pregnancy Outcomes and Neonatal Outcomes
Characteristics of V-safe Pregnancy Registry Participants.
As of March 30, 2021, the v-safe pregnancy registry call center attempted to contact 5230 persons who were vaccinated through February 28, 2021, and who identified during a v-safe survey as pregnant at or shortly after Covid-19 vaccination. Of these, 912 were unreachable, 86 declined to participate, and 274 did not meet inclusion criteria (e.g., were never pregnant, were pregnant but received vaccination more than 30 days before the last menstrual period, or did not provide enough information to determine eligibility). The registry enrolled 3958 participants with vaccination from December 14, 2020, to February 28, 2021, of whom 3719 (94.0%) identified as health care personnel. Among enrolled participants, most were 25 to 44 years of age (98.8%), non-Hispanic White (79.0%), and, at the time of interview, did not report a Covid-19 diagnosis during pregnancy (97.6%) (Table 3). Receipt of a first dose of vaccine meeting registry-eligibility criteria was reported by 92 participants (2.3%) during the periconception period, by 1132 (28.6%) in the first trimester of pregnancy, by 1714 (43.3%) in the second trimester, and by 1019 (25.7%) in the third trimester (1 participant was missing information to determine the timing of vaccination) (Table 3). Among 1040 participants (91.9%) who received a vaccine in the first trimester and 1700 (99.2%) who received a vaccine in the second trimester, initial data had been collected and follow-up scheduled at designated time points approximately 10 to 12 weeks apart; limited follow-up calls had been made at the time of this analysis.
Pregnancy Loss and Neonatal Outcomes in Published Studies and V-safe Pregnancy Registry Participants.
Among 827 participants who had a completed pregnancy, the pregnancy resulted in a live birth in 712 (86.1%), in a spontaneous abortion in 104 (12.6%), in stillbirth in 1 (0.1%), and in other outcomes (induced abortion and ectopic pregnancy) in 10 (1.2%). A total of 96 of 104 spontaneous abortions (92.3%) occurred before 13 weeks of gestation (Table 4), and 700 of 712 pregnancies that resulted in a live birth (98.3%) were among persons who received their first eligible vaccine dose in the third trimester. Adverse outcomes among 724 live-born infants — including 12 sets of multiple gestation — were preterm birth (60 of 636 among those vaccinated before 37 weeks [9.4%]), small size for gestational age (23 of 724 [3.2%]), and major congenital anomalies (16 of 724 [2.2%]); no neonatal deaths were reported at the time of interview. Among the participants with completed pregnancies who reported congenital anomalies, none had received Covid-19 vaccine in the first trimester or periconception period, and no specific pattern of congenital anomalies was observed. Calculated proportions of pregnancy and neonatal outcomes appeared similar to incidences published in the peer-reviewed literature (Table 4).
Adverse-Event Findings on the VAERS
During the analysis period, the VAERS received and processed 221 reports involving Covid-19 vaccination among pregnant persons; 155 (70.1%) involved nonpregnancy-specific adverse events, and 66 (29.9%) involved pregnancy- or neonatal-specific adverse events (Table S4). The most frequently reported pregnancy-related adverse events were spontaneous abortion (46 cases; 37 in the first trimester, 2 in the second trimester, and 7 in which the trimester was unknown or not reported), followed by stillbirth, premature rupture of membranes, and vaginal bleeding, with 3 reports for each. No congenital anomalies were reported to the VAERS, a requirement under the EUAs.
