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Which inactivated vaccines still contain thimerosal as a preservative in 2025?
Executive summary
As of the sources provided through mid‑2025, thimerosal (a mercury‑based preservative) had been largely removed from most U.S. childhood vaccines and was used mainly in some seasonal influenza vaccines — but U.S. advisers moved in June–July 2025 to phase it out of all flu vaccines distributed in the United States (ACIP/HHS action) [1] [2]. Reporting and government documents also note that only a small share of flu doses still contained thimerosal in 2024–25 — estimates in the public record range from about 4% of flu vaccines overall to higher counts of formulations on the market — and that regulators and professional societies continue to say thimerosal is safe based on past studies [3] [4] [5].
1. What vaccines historically did and did not contain thimerosal — the baseline
Government summaries and reviews state that several routine childhood vaccines “never contained thimerosal,” explicitly naming measles‑mumps‑rubella (MMR), varicella (chickenpox), inactivated polio vaccine (IPV), and pneumococcal conjugate vaccine as never having included it [6] [7] [8]. The FDA and CDC also document that thimerosal was widely used in the past in multi‑dose vials of some vaccines but was largely removed from the childhood schedule beginning around 1999–2001 as manufacturers moved to single‑dose presentations [5] [8].
2. In 2024–25, where thimerosal still showed up — mainly influenza vaccines
Multiple contemporary reports say that by the 2024–25 influenza season most flu vaccines did not contain thimerosal but a minority did: one CDC document cited in fact‑checks and reporting put thimerosal‑containing flu vaccines at roughly 4% of doses for 2024–25, and other reporting counted multiple flu formulations licensed for the season [3] [4] [9]. CDC/ACIP slide material and the 2025–26 influenza recommendations confirm 94% (in a slide deck) or similar majorities of influenza vaccines were thimerosal‑free, leaving only a small portion in multi‑dose vials that used the preservative [7] [3].
3. Policy change in mid‑2025: advisers and HHS moved to remove thimerosal from all U.S. flu vaccines
In June 2025 the CDC’s Advisory Committee on Immunization Practices recommended using only single‑dose influenza vaccines free of thimerosal for children, pregnant women and adults; HHS later adopted an ACIP recommendation to remove thimerosal from all influenza vaccines distributed in the U.S. in July 2025 [1] [2]. Reporting frames this as a policy decision to prefer thimerosal‑free single‑dose formulations even though thimerosal had been rare for years [10] [11].
4. Safety consensus vs. political controversy — two competing narratives
Longstanding scientific reviews and public health agencies conclude available evidence does not show harm from thimerosal in vaccines and that its removal from childhood vaccines was precautionary; professional societies such as the American Academy of Pediatrics have said research supports safety [8] [12]. At the same time, the mid‑2025 move to remove thimerosal from flu vaccines was driven partly by political pressure and advisory votes and drew criticism that the action could feed vaccine skepticism — reporting notes activists and some advisers framed the step as necessary while some experts warned it was not evidence‑driven [13] [10] [12].
5. Practical answer to the user question: which inactivated vaccines still contained thimerosal in 2025?
Available sources say that by the 2024–25 season the main category of inactivated vaccines that still contained thimerosal was seasonal influenza vaccines presented in multi‑dose vials; other commonly used inactivated vaccines such as inactivated polio vaccine have never contained thimerosal [7] [8]. CDC/press reporting indicates only a small fraction of flu doses still used thimerosal in 2024–25, and ACIP/HHS actions in June–July 2025 aimed to remove thimerosal from all U.S. influenza vaccines going forward [3] [1] [2].
6. Limitations and what reporting does not say
The sources provided do not give an exhaustive manufacturer‑by‑manufacturer list of every vaccine lot or every country’s products in 2025; they focus on U.S. policy and the U.S. vaccine market [5] [2]. If you need a vaccine‑level, current list (manufacturer, product name, formulation and whether a given lot contains thimerosal), that level of detail is not contained in these sources and would require checking FDA product labels or manufacturer factsheets for each vaccine (not found in current reporting) [5].
7. Bottom line for readers and clinicians
As reported in mid‑2025, thimerosal was largely absent from the U.S. childhood immunization schedule and remained only in a small share of seasonal influenza multi‑dose vials — but U.S. advisers and HHS moved to eliminate thimerosal from all flu vaccines distributed in the United States, shifting policy toward exclusively thimerosal‑free flu shots [7] [1] [2]. The scientific literature and major health agencies cited in these sources continue to say studies do not support harm from thimerosal, even as the policy change reflects political and advisory priorities [8] [12].