Toxicokinetics of mercury after long-term repeated exposure to thimerosal-containing vaccine – Source: Toxicological Sciences, Jan 20, 2011

The preservative thimerosal contains ethyl mercury (EtHg). Concerns over possible toxicity have reemerged recently, due to its presence in (swine and other) flu vaccines.

We examined the potential accumulation of mercury in adults given repeated injections of a thimerosal-preserved vaccine for many years.

Fifteen female patients were recruited from an outpatient clinic running a clinical trial with repeated injections (1 mL every 3-4 weeks) of a staphylococcus toxoid vaccine containing 0.01% thimerosal, to treat chronic fatigue syndrome. Fifteen untreated female patients with the same diagnoses served as controls. Blood samples were taken before injecting the vaccine, one day later, about two weeks later, and just before the next injection.

In the fifteen controls, samples were taken twice. Blood was analyzed for total mercury and EtHg. The toxicokinetics were assessed for each patient separately, as well as with a population-based pharmacokinetic model. Total mercury in blood increased on day one in all treated patients (median 0.33, range 0.17-1.3 ?g/L), as did EtHg (median 0.14 ?g/L, range 0.06-0.43 ?g/L). After a few weeks levels were back to normal and similar to those in controls.

Levels of methyl mercury (MeHg; from fish consumption) were much higher than those of EtHg.

After exclusion of an outlier, the mean half-life in a population-based model was 5.6 (95% confidence interval 4.8-6.3) days.

The results indicate that mercury from thimerosal is not accumulated in blood in adults. This is in accordance with:

• Short half-lives

• And rapid metabolism of EtHg to inorganic mercury.

Source: Toxicological Sciences, Jan 20, 2011. Barregard L, Rekic D, Horvat M, Elmberg L, Lundh T, Zachrisson O. Department of Occupational and Environmental Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden. [E-mail:;]

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