Did any 2025 inactivated hepatitis A or B vaccines include thimerosal in multi-dose vials or single-dose formulations?
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Executive summary
Available sources show that thimerosal — a mercury-containing preservative used historically in multi-dose vaccine vials — was largely phased out of hepatitis B vaccine formulations in the United States beginning around 1999 and has been largely absent from single‑dose hepatitis B products since then [1] [2]. Recent federal slide decks and reviews (2024–2025) treat thimerosal as primarily an issue for multi‑dose vials (not single‑dose hepatitis B vaccines) and note limited remaining use of thimerosal in some vaccines (notably certain influenza presentations), but they do not identify newly introduced thimerosal‑containing hepatitis A or B single‑dose products in 2025 [3] [4] [5].
1. Historical phase‑out: why thimerosal disappeared from hepatitis B vials
Public‑health agencies and manufacturers began removing thimerosal from many childhood vaccines as a precautionary step in the late 1990s; CDC notices from that era describe the availability and expansion of thimerosal‑free hepatitis B vaccines and indicate industry moves to stop using thimerosal in hepatitis B formulations beginning in 1999 [1] [6]. Contemporary reporting and reviews reiterate that thimerosal‑containing hepatitis B vaccines were removed from the U.S. market starting in 1999 [2].
2. How regulators describe thimerosal’s current role in vaccines
FDA and CDC materials explain that thimerosal’s primary use today is as a preservative in multi‑dose vials to prevent microbial contamination when a vial is accessed multiple times; they emphasize that many vaccines have never contained thimerosal and that its remaining role is limited to certain multi‑dose formulations such as some influenza vaccines [4] [5] [3]. CDC slide packages in 2024–2025 discuss thimerosal‑containing vaccines in the context of influenza supply and safety reviews rather than new hepatitis A/B formulations [3].
3. What 2025 reporting says specifically about hepatitis A and B products
The searchable 2025 reviews and guidance cited here focus on hepatitis B safety (including historical studies comparing thimerosal‑containing and thimerosal‑free hepatitis B vaccines) and on ACIP discussions about thimerosal broadly; none of the provided documents report introduction in 2025 of thimerosal‑containing hepatitis A or hepatitis B single‑dose vaccines or return of thimerosal to standard hepatitis B single‑dose products [7] [3] [5]. A December 2025 clinical review notes that thimerosal‑containing hepatitis B vaccines were removed from the market beginning in 1999, reinforcing the long‑standing absence of such formulations from routine single‑dose hepatitis B options [2].
4. Where thimerosal still appears in the modern vaccine supply
Multiple sources state that thimerosal is still used in certain multi‑dose vials for some vaccines because it prevents bacterial or fungal growth when a vial is punctured repeatedly; the FDA and CDC explicitly note its continued use in some multi‑dose influenza and other presentations, not in routine single‑dose hepatitis B products referenced in available reporting [4] [5] [3].
5. Evidence and safety debates remain part of the record
There is a substantive literature — and ongoing debate in some quarters — about thimerosal and health outcomes, including historical epidemiologic analyses using Vaccine Safety Datalink records and other observational studies; federal slide decks and peer‑reviewed work reviewed in 2024–2025 address safety outcomes after exposure to thimerosal‑containing hepatitis B vaccines in earlier decades [7] [8] [9]. Public commentary and news coverage also record disagreement among experts and advocacy figures over policy decisions that have involved thimerosal [10] [11].
6. Limitations and what the sources do not say
Available sources do not list any specific 2025‑marketed hepatitis A or hepatitis B vaccine that reintroduced thimerosal into single‑dose or multi‑dose hepatitis vials; they do not provide explicit manufacturer product‑by‑product labeling for every lot distributed in 2025, so they cannot rule out isolated or legacy multi‑dose supplies still on hand at local levels [3] [5]. Manufacturer lot labels and FDA product inserts would be the definitive source to confirm whether any specific 2025 vial contained thimerosal; those documents are not included in the provided material (not found in current reporting).
Bottom line: federal public‑health documents and reporting through 2025 describe thimerosal as largely removed from hepatitis B vaccines since 1999 and as primarily a preservative used today in certain multi‑dose vials (not single‑dose hepatitis B products). The materials supplied here contain no explicit evidence that any newly marketed 2025 inactivated hepatitis A or B single‑dose vaccines included thimerosal; they instead frame remaining thimerosal use as tied to multi‑dose presentations and to older product histories [1] [4] [3] [2].