Why Independent Scientists Are Re-Examining Tdap Vaccine Safety in Pregnancy—And What They're Looking For

An independent scientific review of the tetanus, diphtheria, and pertussis (Tdap) vaccine in pregnancy is launching to address growing vaccine skepticism and provide updated evidence on safety and effectiveness. The Vaccine Integrity Project (VIP) at the University of Minnesota's Center for Infectious Disease Research and Policy (CIDRAP) announced it will systematically examine decades of data on how this vaccine protects pregnant women and their newborns, with findings expected this spring.

What Exactly Is the Tdap Vaccine Reviewing?

The Tdap vaccine protects against three serious bacterial infections: tetanus, diphtheria, and pertussis (whooping cough). When given during pregnancy, the vaccine helps protect newborns during their most vulnerable months—before they're old enough to receive their own vaccinations. The VIP review will examine a comprehensive range of safety outcomes and effectiveness data that has accumulated over recent years.

The independent review will assess possible safety concerns including miscarriage, stillbirth, preterm birth, pregnancy-related high blood pressure disorders, congenital anomalies such as spina bifida, and newborn developmental outcomes. Researchers will also evaluate reported data on how effectively the vaccine prevents tetanus, diphtheria, and pertussis in both pregnant adults and newborns.

Why Launch This Review Now?

The timing of this review reflects a broader shift in the vaccine policy landscape. The most recent comprehensive federal review of Tdap vaccine evidence was published in January 2020, and the federal Advisory Committee on Immunization Practices (ACIP) last formally reviewed and voted on recommendations for Tdap during pregnancy in 2012. Meanwhile, recent appointees to ACIP have questioned—without scientific evidence—the safety of vaccines given during pregnancy, including the four vaccines recommended to protect pregnant women and their babies: Tdap, influenza, respiratory syncytial virus (RSV), and COVID-19.

"An evidence-based review will help the public not only understand how vaccination reduces neonatal pertussis infections and hospitalizations but also how changes in vaccine uptake could affect these outcomes," said Dr. Brenna L. Hughes, chair of the Society for Maternal-Fetal Medicine's Committee on Infectious Diseases and Emerging Threats.

What Do Experts Expect to Find?

Medical professionals who have reviewed the accumulating evidence are optimistic about what the independent analysis will reveal. Dr. Kevin Ault of the American College of Obstetricians and Gynecology's Expert Work Group on Immunization, Infectious Disease, and Public Health Preparedness expressed confidence in the vaccine's track record: "I think if you get all these studies in one place, you're going to see 80% or 90% effectiveness in the first few months of life. Pertussis, of course, can be deadly in the first few months of life, and we've seen some unvaccinated children, unfortunately, die in the past year or two in the United States of that".

Dr. Ault also noted that substantial new evidence has emerged in recent years supporting both the safety and effectiveness of the vaccine. "We have the new adult acellular vaccine, and the data look great. Every time I see one of those studies, I'm like, 'wow, this is really an intervention that works against a horrible disease,'" he explained.

How Will the Review Be Conducted?

The Evidence Foundation, a nonprofit organization focused on improving health outcomes through evidence-based research, is conducting the Tdap review in collaboration with CIDRAP. The assessment will follow established standards for systematic evidence review to ensure scientific rigor and transparency.

• Methodology: The review will use a pre-specified protocol, structured evaluation of bias, and transparent reporting of findings to maintain scientific integrity.
• Public Registration: The protocol will be publicly registered to foster methodological transparency and allow independent scrutiny of the review process.
• Timeline: VIP expects to release the Tdap findings this spring, with the final report and supporting materials made publicly available to support clinicians and medical professional societies.

What Happens After the Review Is Complete?

Michael Osterholm, PhD, MPH, director of CIDRAP, explained the broader purpose of this work: "Our intent is to provide support of the vaccine's safety and efficacy, giving clinicians and moms the peace of mind that an independent review has found that vaccines routinely administered during pregnancy are safe and effective". The review represents an effort to fill gaps left by federal agencies during a period of policy uncertainty and vaccine skepticism.

The Tdap review is part of a larger VIP initiative examining vaccines recommended during pregnancy. The project recently announced it will update its 2025 evidence review of influenza, COVID-19, and respiratory syncytial virus (RSV) vaccines, which concluded that the 2025-26 vaccines were safe and effective. The updated analysis will be completed before the start of the 2026-27 respiratory virus season and will incorporate newly published data.

VIP is also reviewing the safety and effectiveness of the human papillomavirus (HPV) vaccine and previously completed an independent assessment of the hepatitis B birth dose. These evaluations aim to ensure that vaccination policy discussions stay grounded in rigorous scientific analysis and transparent evaluation of the risks and benefits.