Making sense of epidemiological studies of young children exposed to thimerosal in vaccines.
OBJECTIVE
To compare epidemiological studies dealing with neurological issues (compatible with Hg toxicity) linked to exposing newborns and infants to intramuscular doses of preservative-Hg resulting from vaccination with thimerosal-containing vaccines (TCV).


METHODS
Major databases were searched for studies that addressed neurodevelopment outcomes other than autism. Eight studies were identified and compared.


RESULTS
Information extracted from the studies done in the USA, the UK, and Italy is important in understanding the complex interplay of variables but insufficient to establish non-toxicity for infants and young children still receiving TCV: a) there is ambiguity in some studies reporting neurodevelopment outcomes that seem to depend on confounding variables; b) the risk of neurotoxicity due to low doses of thimerosal is plausible at least for susceptible infants; c) there is a need to address these issues in less developed countries still using TCV in pregnant mothers, newborns, and young children.


CONCLUSIONS
Since the use of TCV is still inevitable in many countries, this increases the need to protect vulnerable infants and promote actions that strengthen neurodevelopment. Developing countries should intensify campaigns that include breastfeeding among efforts to help prime the central nervous system to tolerate exposure to neurotoxic substances, especially thimerosal-Hg.
Dórea
José G
JG
C.P. 04322, Universidade de Brasilia, 70919-970 Brasilia, DF, Brazil. dorea@rudah.com.br
D002658:Developmental Disabilities / Q000453:epidemiology / Q000209:etiology; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D020258:Neurotoxicity Syndromes / Q000453:epidemiology / Q000209:etiology*; D011247:Pregnancy; D011310:Preservatives, Pharmaceutical / Q000009:adverse effects; D013849:Thimerosal / Q000009:adverse effects*; D014612:Vaccines / Q000009:adverse effects* / Q000737:chemistry
D011310:Preservatives, Pharmaceutical; D014612:Vaccines; D013849:Thimerosal