The messages come from a trove that Sen. Rand Paul (R-Ky.) and Sen. Ron Johnson (R-Wis.) released, containing more than 34,000 texts and 522 voicemails the Senate Homeland Security Committee pulled from Fauci's government-issued phone. Among the trove is a January 2021 text chain between Fauci, Dr. Vivek Murthy and Dr. Rochelle Walensky, who went on to serve as the Biden administration's surgeon general and CDC director, in which the three officials worked through how the vaccine's risks might interact with pregnancy.

On Jan. 25, Murthy opened the thread with a question. "For pregnant women considering getting the vaccine, are you aware of any data or theoretical reason why vaccinating early vs late in pregnancy would be preferred? And any sense of when there will be more robust data on vaccine risk in pregnant women?"

Walensky noted that more than 15,000 pregnant women had already enrolled in the CDC's V-safe vaccine safety monitoring system. Fauci wrote there "are no data or theoretical reason to believe that vaccinating early versus later in pregnancy would be preferred." He also flagged a caveat that would later look prescient. "Yet, some people (even female health care professionals) feel concerned about injecting a 'genetic' vaccine very early in pregnancy," he wrote.