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The Centers for Disease Control and Prevention walked back a statement its director made on Friday about the agency’s recommendation surrounding the COVID-19 vaccine during pregnancy, clarifying that the agency’s recommendation for pregnant people considering the vaccine has not changed.

Speaking at a White House COVID-19 briefing on Friday, CDC head Dr. Rochelle Walensky  said that the “CDC recommends that pregnant people receive the COVID-19 vaccine,” citing a new study that found no evidence to suggest that the Pfizer and Moderna COVID-19 vaccines pose risk during pregnancy.

On Tuesday, the agency walked back that recommendation. In an email to CBS News, a CDC spokesperson said the CDC’s guidance for pregnant people had not changed from its March recommendation, which is that “pregnant people are eligible and can receive a COVID-19 vaccine” and clarified that the guidance “has always been and remains CDC’s recommendation.”

“If facing decisions about whether to receive a COVID-19 vaccine while pregnant, people should consider risk of exposure to COVID-19, the increased risk of severe infection while pregnant,  the known benefits of vaccination, and the limited but growing evidence about the safety of COVID-19 vaccine during pregnancy,” a CDC spokesperson said in an emailed statement.

Walensky’s comments on Friday followed the publication of a peer-reviewed paper in The New England Journal of Medicine. In the report, researchers from the CDC used self-reported data from more than 35,691 people who were either pregnant or soon to become pregnant. After getting the shot, they reported typical vaccine side effects — pain at the injection site, fatigue, headaches and muscle aches — but researchers say the data “did not show obvious safety signals.”

The results were an extension of a study presented by the CDC’s Advisory Committee on Immunization Practices last month, which also found no safety concerns during pregnancy.

Walensky’s comments differed from the guidelines posted on the CDC’s website. The agency’s website says that “based on how these vaccines work in the body, experts believe they are unlikely to pose a specific risk for people who are pregnant,” while acknowledging that limited data existed on the safety of the COVID-19 vaccine among pregnant people.

The results of the study published Wednesday add to mounting evidence that suggests the vaccine is as safe for pregnant patients as it is for non-pregnant individuals. The American College of Obstetrics and Gynecologists, a leading professional medical organization, recommends that COVID-19 vaccines not be withheld from pregnant or breastfeeding patients.

Pregnant people are particularly vulnerable to more severe illness from COVID-19. According to data published by the CDC, those who contract the virus during pregnancy are more likely to be hospitalized and face a higher risk of death.

Wednesday’s paper used data collected through three methods: V-safe, a CDC-sponsored program that collects vaccine side effect data using smartphones; the v-safe pregnancy registry; and Vaccine Adverse Event Reporting System (VAERS), a longstanding joint surveillance effort between the CDC and the Food and Drug Administration that collects adverse vaccine reports. All of the data used in the research was self-reported.

According to the study’s results, pregnant patients reported pain at the vaccine’s injection site at a slightly higher rate than their non-pregnant peers, but were less likely to say they experienced headache, muscle pain, chills, and fever. Among the 827 study participants who completed their pregnancy, the rate of miscarriage was consistent with pregnancy outcomes prior to the pandemic, according to the researchers.

However, no data yet exists on pregnancy outcomes for patients given the vaccine in their first trimester.

Researchers acknowledged that “more longitudinal follow-up, including follow-up of large numbers of women vaccinated earlier in pregnancy, is necessary to inform maternal, pregnancy, and infant outcomes.”