The public health official’s private texts show that he wrestled with many doubts that he later characterized as misinformation when they were uttered aloud by critics.
On Monday, Republican senators Rand Paul of Kentucky and Ron Johnson of Wisconsin—both fierce critics of Anthony Fauci—released a number of pandemic-era text messages from the former head of the National Institute of Allergy and Infectious Diseases (NIAID). One exchange in particular has raised the ire of his many critics.
In January 2021, Fauci exchanged a series of texts with then–Surgeon General Vivek Murthy and Rochelle Walensky, the head of the Centers for Disease Control and Prevention (CDC) during the Biden administration, about whether it was safe for pregnant women to take the Covid vaccine. After the first messages, Fauci wrote another one two hours later.
“I asked around a bit more and another issue came up that you need to be aware of. Since many people have significant cytokines storm and fever after the 2nd dose, this theoretically could be associated with miscarriage in the 1st trimester,” he wrote. Cytokines include inflammatory molecules that catalyze attacks inside the body.
A few days later, Fauci noted that pregnant women had to evaluate “the potential risks versus the benefits” of taking the vaccine. But then, in a public discussion with Howard Bauchner, the editor in chief of The Journal of the American Medical Association, Fauci said flatly that the CDC had found “no red flags” in a Covid vaccine study that included 10,000 pregnant women. His public confidence, of course, was at odds with the private hypotheses he had discussed with Murthy and Walensky.
I was a professor of epidemiology at the University of California, San Francisco during Covid, and a critic of much of the government’s response to the pandemic. At an absolute minimum, the disclosed text messages reveal concerning facts about our Covid vaccine response. There was more uncertainty than officials were willing to let on to the public. And as the public has learned that officials were not being straight with them, their faith in public-health efforts has been badly damaged.
During the Covid-19 pandemic pregnant women were at higher risk of bad outcomes, such as death or intensive care unit admission, than women who were not pregnant. Estimates vary but three to seven times higher risks from being pregnant are broadly accepted. To put this in perspective, age was also a risk factor: An 80-year-old had at least 1,000 times the risk of an 8-year-old. Pregnancy was a risk factor, but not nearly as severe as age.
Vaccines during pregnancy had a rationale—to protect the mother, and if administered late enough, antibodies could also pass to the baby, theoretically helping in the first few months after birth. But as to whether vaccines were “safe” for pregnant women, or whether they increased miscarriages or birth defects—the answer is we still don’t know. And we are unlikely ever to know.
Many commenters will say something like: Covid vaccines have been given to hundreds of thousands of pregnant women and we haven’t seen any concerning signals. The statement is true. But it’s also misleading. When vaccines are given to pregnant women, they are preferentially given to those with access to healthcare, who are health-conscious, and who desire and are willing to receive those vaccines. These women are a very different cohort from women who do not choose to get vaccinated. If a vaccine increased the rate of miscarriage twentyfold, you would see it, and we know it doesn’t do that—but if there were a subtle increase like a five or even a 10 percent increase in miscarriage, there is no observational system capable of detecting it.
There was more uncertainty than officials were willing to let on to the public.
Put another way, the kind of women who are likely to choose vaccination may have been destined to have fewer miscarriages and birth defects in the first place. Maybe a vaccine could worsen outcomes for this group, but that safety signal is hidden by comparing them to women who don’t get a vaccine who were, at baseline, a slightly higher risk. On a technical note: Even case control studies suffer from bias and are inadequate to exclude modest risks.
Instead, since it’s well accepted that pregnant women who choose to get vaccinated and those who do not are not comparable, scientists favor randomized trials to determine what effect the vaccine has on pregnant women. To test a vaccine, one group of pregnant women would be immunized, and the other group would not.
In fact, there was one such trial that was conducted and produced some preliminary results during the Covid-19 pandemic. It is currently on the vaccine label for the Pfizer mRNA vaccine called Comirnaty. This trial enrolled women who were predominantly 24 weeks or beyond in pregnancy. It showed a numerical increase in major and minor birth defects, but it did not reach statistical significance. The trial was halted when only 300 women out of a planned 4,000 were randomized. Instead of seeing it through, the American College of Obstetricians and Gynecologists unilaterally recommended vaccines to all pregnant women, sabotaging the trial’s purpose. Let me be clear: This was an error.
What about getting a Covid shot early in a pregnancy, before week 24, as many experts endorse? We altogether lack good evidence about vaccines early in pregnancy. It is possible Covid-19 vaccines increase miscarriage when administered early. A good scientist cannot say whether this is true or not. Again, we don’t know. Companies should have been compelled to study this issue with a similar trial.
In 2026, of course, the lethality and severity of Covid-19 in pregnant women is completely diminished. Covid is not the devastating force it once was. Whether vaccinating a mother close to delivery protects the baby is still a hypothesis in need of study, but the risk to a pregnant woman is not a salient concern.
Some argue that we cannot ethically do these studies in pregnant women. This is a misguided argument—and the reason why medical science around pregnancy is lacking. In fact, it is unethical not to do these studies. In the absence of these studies, Fauci and others gave false reassurance. Just because the CDC did not flag a safety issue with 20,000 women, as Fauci’s texts suggest, doesn’t mean it doesn’t exist. In fact, there are lots of reasons for it to be hidden.
I recognized the poor evidence base for Covid vaccines broadly when I served as the head vaccine regulator of the FDA. My 2025 Covid-19 framework in The New England Journal of Medicine preserved Covid vaccines as an option for pregnant women, but was by no means a recommendation. Like many doctors, my personal recommendation is not to receive one during pregnancy until the sponsor conducts the appropriate randomized trial and shows an unequivocal benefit. I am not holding my breath.
These products have produced tremendous revenues for companies that have little incentive to run studies that can only reduce their market share. The moment the ob-gyn association gave vaccine makers carte blanche to vaccinate pregnant women, the trial was dead.
Fauci’s private texts show that he wrestled with many doubts that he later characterized as misinformation when they were uttered aloud by critics. Ultimately, officials like Fauci were too keen on pushing vaccines to everyone—young children, pregnant women, and people who already had Covid—and not eager enough to run the appropriate studies needed to settle the doubts. For a man who declared himself as science, it’s a pity he didn’t champion more of it.