A comparative pharmacokinetic estimate of mercury in U.S. Infants following yearly exposures to inactivated influenza vaccines containing thimerosal.
Level 5 - mechanism / opinion, no new human data
Pharmacokinetic simulation and risk modeling based on non-human primate kinetic data, without primary human clinical trial data.
PubMed 24117921 · doi:10.1111/risa.12124
What was done
Researchers modeled and compared the infant body burden of mercury resulting from scheduled yearly exposures to thimerosal in multidose inactivated influenza vaccines versus daily dietary methylmercury exposure at the U.S. Environmental Protection Agency (EPA) reference dose. Pharmacokinetic parameters were derived from prior empirical experiments in infant monkeys receiving identical episodic doses of thimerosal or methylmercury. Cumulative exposure (area under the curve) and peak body burdens were estimated over the first 4.5 years of life, including scenarios for low-birth-weight infants.
What was found
The modeled cumulative mercury body burden (AUC) in infants over the first 4.5 years of life from annual thimerosal-containing influenza vaccines was two orders of magnitude lower than the lowest regulatory safety threshold for methylmercury over the same timeframe. Specific numerical values were not reported in the abstract. Under worst-case modeling assumptions, peak episodic mercury burdens never exceeded the established safe body burden reference level for methylmercury at any point, including in low-birth-weight infants.
Why it matters
The findings provide quantitative pharmacokinetic support for the safety margins of residual thimerosal preservative use in multidose pediatric influenza vaccines relative to federal safety thresholds.
Limits
The study is a theoretical pharmacokinetic simulation rather than a clinical measurement in human infants. Key kinetic parameters were extrapolated from infant monkey data. The abstract reports relative comparisons rather than exact absolute concentrations, half-lives, or confidence intervals.
Cited by
- supports Around the year 2000, thimerosal was removed from most childhood vaccines in the United States, remaining primarily in multi-dose influenza vaccines and select others.