What You Need to Know: Thimerosal, Flu Shots, and Access for Pregnant People & Kids

Imagine going in for your baby’s or your own flu shot, only to find that it’s now officially guaranteed to be entirely preservative-free. That’s the new reality: as of mid-2025, all flu shots given to children, pregnant people, and adults throughout the U.S. will be single-dose, thimerosal-free. For many, this is a long-awaited change; for others, it sparks questions about what’s real, what’s risky—and what this means for availability and coverage.

The Change That Just Went Live

In July 2025, the Department of Health and Human Services approved a recommendation from the CDC’s Advisory Committee on Immunization Practices to remove the mercury-based preservative thimerosal from all influenza vaccine doses in single-dose formulations for every age group—children, pregnant people, and adults. The key vote was 5-1 at the June ACIP meeting, with only one member dissenting. The decision caps off decades of public health efforts to reduce mercury exposure, even though most flu vaccines already avoid the ingredient. Before this mandate, about 96% of flu vaccinations in the U.S. came from thimerosal-free sources; only roughly 4% involved multi-dose vials that contain the preservative. These ranged mostly across adult vaccines and multi-dose supply buffers. (Children’s vaccines were already effectively thimerosal-free since 2001.)

Safety, Scientists, and Skepticism

One of the strongest realities backing this policy is that no credible scientific study has ever shown harm from the low doses of thimerosal used in vaccines. Regulatory agencies—including the FDA and CDC—continue to affirm that ethyl-mercury in thimerosal is processed differently (and far more safely) than the methyl-mercury found in certain fish. Studies over decades show zero link between thimerosal exposure via vaccination and developmental disorders like autism. The decision to remove it was more about public confidence and precaution than new evidence of harm.

What This Means for Flu Coverage & Access

Here’s where the picture gets more complex. In recent flu seasons, coverage has been less than stellar—particularly among pregnant women and children. In the 2023-24 flu season, only 47.4% of pregnant persons reported they got the flu shot before or during pregnancy. That rate dropped sharply during early pregnancy, with about 35% having received their flu vaccine by mid-season according to some health-record data. Among children, coverage has also slid: roughly half of all kids under 18 were vaccinated in 2024-25—well under ideal levels.

Experts worry that removing even the small number of multi-dose vials could squeeze access in rural or low-resource areas where cost, storage, and transport make single-dose vials harder to scale. Some clinics serve remote populations and rely on multi-dose supplies to stretch budgets. With single-dose formulations now the norm, costs per dose, waste, and logistical burdens may increase unless federal support keeps up.

Free Flu Shots Near You: Where They Are and How to Find One

• Many public health departments offer complimentary annual flu clinics; large cities often roll out multiple free-shot sites in neighborhoods.
• Community hospitals, faith-based organizations, and free clinics are still key access points—especially for uninsured or underinsured people.
• Pharmacies—including big chains—often provide flu vaccines at no out-of-pocket cost for those with insurance thanks to preventive care mandates; ask if you’re unsure of coverage.
• Programs like Vaccines for Children ensure that kids under 19 can get free flu shots even without insurance, if their providers participate.
• It’s a smart move to call ahead or use state or local health-department websites: supply of single-dose, thimerosal-free flu vaccine may vary by site and location.

Real-World Case: Philadelphia & Southern California

In Philadelphia, city health centers have offered walk-in free flu and COVID-19 vaccinations to people aged 6 months and older with no appointment—making flu shots as easy as going to your neighborhood clinic. In Pasadena and nearby communities, hospitals and public-health partners have held free clinics throughout the fall offering flu immunizations with no insurance needed. These programs demonstrate what’s possible when availability, convenience, and cost barriers are eliminated.

Why This Still Matters

Pregnancy is high risk when it comes to influenza. People who are pregnant are more likely to be hospitalized from the flu, and infection can also harm fetal health. Yet, in the 2023-24 season, fewer than half of pregnant persons received their flu vaccine. That’s despite ACIP’s long-standing recommendation: everyone aged 6 months and older should be vaccinated. Flu vaccine effectiveness typically ranges between 30-60% depending on strain match—but even a modest protection early in pregnancy can mean fewer hospital visits, reduced risk of complications, and less strain on the health system.

Waning trust is a real concern. Controversies about vaccine policy, especially around thimerosal, can fuel hesitancy. Health authorities will need to help people understand why this change happened—why, even though most shots were already thimerosal-free, this matters—and why choosing to vaccinate remains one of the safest actions for at-risk groups.

This shift isn’t just about removing a preservative—it’s about showing that public health policy responds to public concerns. But removing thimerosal won’t, by itself, fix flu-shot gaps. It’s the follow-through—ensuring vaccine availability, educating people, making clinics accessible—that counts.