Professor Emeritus, Faculty of Health Sciences, Universidade de Brasilia, 70919-970 Brasilia, DF, Brazil.
Environ Res. 2017 Jan;152:280-293. doi: 10.1016/j.envres.2016.10.028. Epub 2016 Nov 3.
Vaccines are prophylactics used as the first line of intervention to prevent, control and eradicate infectious diseases. Young children (before the age of six months) are the demographic group most exposed to recommended/mandatory vaccines preserved with Thimerosal and its metabolite ethylmercury (EtHg). Particularly in the less-developed countries, newborns, neonates, and young children are exposed to EtHg because it is still in several of their pediatric vaccines and mothers are often immunized with Thimerosal-containing vaccines (TCVs) during pregnancy. While the immunogenic component of the product has undergone more rigorous testing, Thimerosal, known to have neurotoxic effects even at low doses, has not been scrutinized for the limit of tolerance alone or in combination with adjuvant-Al during immaturity or developmental periods (pregnant women, newborns, infants, and young children). Scientific evidence has shown the potential hazards of Thimerosal in experiments that modeled vaccine-EtHg concentrations. Observational population studies have revealed uncertainties related to neurological effects. However, consistently, they showed a link of EtHg with risk of certain neurodevelopment disorders, such as tic disorder, while clearly revealing the benefits of removing Thimerosal from children's vaccines (associated with immunological reactions) in developed countries. So far, only rich countries have benefited from withdrawing the risk of exposing young children to EtHg. Regarding Thimerosal administered to the very young, we have sufficient studies that characterize a state of uncertainty: the collective evidence strongly suggests that Thimerosal exposure is associated with adverse neurodevelopmental outcomes. It is claimed that the continued use of Thimerosal in the less-developed countries is due to the cost to change to another preservative, such as 2-phenoxyethanol. However, the estimated cost increase per child in the first year of life is lower than estimated lifetime cost of caring for a child with a neurodevelopmental disorder, such tic disorder. The evidence indicates that Thimerosal-free vaccine options should be made available in developing countries.
疫苗是预防、控制和消灭传染病的第一道防线。幼儿（六个月以下）是接触推荐/强制疫苗（含硫柳汞及其代谢物乙基汞（EtHg））最多的人群。特别是在欠发达国家，新生儿、婴儿和幼儿仍会接触到 EtHg，因为它仍存在于他们的几种儿科疫苗中，而母亲在怀孕期间经常接种含硫柳汞的疫苗（TCVs）。虽然产品的免疫原性成分经过了更严格的测试，但硫柳汞即使在低剂量下也具有神经毒性作用，其单独或与佐剂-Al 在不成熟或发育期间（孕妇、新生儿、婴儿和幼儿）的耐受限度都没有受到严格审查。科学证据表明，实验中疫苗-EtHg 浓度模型表明了硫柳汞的潜在危害。观察性人群研究揭示了与神经影响相关的不确定性。然而，一致的是，它们表明 EtHg 与某些神经发育障碍（如抽动障碍）的风险有关，同时明确显示了在发达国家从儿童疫苗中去除硫柳汞（与免疫反应相关）的好处。到目前为止，只有富裕国家受益于使幼儿免受 EtHg 的暴露。关于给非常年幼的儿童接种硫柳汞，我们有足够的研究来描述一种不确定的状态：集体证据强烈表明，硫柳汞暴露与不良神经发育结果有关。据称，在欠发达国家继续使用硫柳汞是因为改用另一种防腐剂（如 2-苯氧乙醇）的成本。然而，在生命的第一年，每个孩子的估计成本增加低于照顾患有神经发育障碍（如抽动障碍）的孩子的终身成本。有证据表明，应在发展中国家提供不含硫柳汞的疫苗选择。
