Mercury Levels in Premature and Low Birth Weight Newborn Infants after Receipt of Thimerosal-Containing Vaccines
Received 13 August 2008; received in revised form 9 February 2009; accepted 8 April 2009. published online 29 June 2009.
Objective
We conducted a population-based pharmacokinetic study to assess blood levels and elimination of mercury after vaccination of premature infants born at ≥32 and <37 weeks of gestation and with birth weight ≥2000 but <3000 g.
Study design
Blood, stool, and urine samples were obtained before vaccination and 12 hours to 30 days after vaccination from 72 premature newborn infants. Total mercury levels were measured by atomic absorption.
Results
The mean ± standard deviation (SD) birth weight was 2.4 ± 0.3 kg for the study population. Maximal mean ± SD blood mercury level was 3.6 ± 2.1 ng/mL, occurring at 1 day after vaccination; maximal mean ± SD stool mercury level was 35.4 ± 38.0 ng/g, occurring on day 5 after vaccination; and urine mercury levels were mostly nondetectable. The blood mercury half-life was calculated to be 6.3 (95% CI, 3.85 to 8.77) days, and mercury levels returned to prevaccination levels by day 30.
Conclusions
The blood half-life of intramuscular ethyl mercury from thimerosal in vaccines given to premature infants is substantially shorter than that of oral methyl mercury in adults. Because of the differing pharmacokinetics, exposure guidelines based on oral methyl mercury in adults may not be accurate for children who receive thimerosal-containing vaccines.
ABSTRACT