The current prevalence of vaccine refusals associated with parental safety concerns necessitates the exploration of the connection between vaccines or its ingredients and autism spectrum disorder (ASD). A study conducted by Freed, Clark, Butchart, Singer and Davis (2010) revealed that more than half of 2521 survey respondents believed that there is a strong association between vaccines and autism. Moreover, approximately twelve percent of the survey participants reported that they had not followed recommendations about vaccines and refused administration at least once (Freed et al., 2010). Furthermore, the findings of the study suggest that parental concern about vaccines was significantly higher among parents of Hispanic origin (Freed et al., 2010). Taking into consideration the fact that etiology of ASD in not particularly clear and is still under debate, it is necessary to examine the current literature pertaining to the assessment of the link between vaccine administration and ASD (Freed et al., 2010).
An article written by Price et al. presents the results of a study examining the connection between prenatal and infant ethylmercury exposure associated with the use of ethylmercury in vaccines and immunoglobulin preparations and autistic disorder (AD), ASD, and ASD with regression (2010). The study was conducted on a sample size of 256 children diagnosed with ASD using the control group of 752 subjects of the same age and gender (Price et al., 2010). Children’s exposure (prenatal and postnatal) to thimerosal was verified with the help of immunization records. A conditional logistic regression model was applied in order to determine the degree of association between ASD, AD, and ASD with regression and exposure to thimerosal during different periods of child development.
Results of the study suggested that there is no association between ethylmercury exposure and increased risk of ASDs (Price et al., 2010). A case-control study conducted by DeStefano, Price and Weintraub (2013) confirms Price et al.’s findings and suggests that there is no relationship between increasing exposure to organomercury compounds and risk of developing some form of ASDs. However, the authors suggest that there is a chance that immunologic stimulation caused by vaccines containing antigens could be accountable for the development of ASD during the first years of life (DeStefano, 2013). Therefore, this possibility should be further investigated.
Another study aimed at the exploration of the link between exposure to thimerosal-containing vaccine and the increased risk of different ASDs was conducted by Geier, Hooker, Kern, King and Geier in 2013. The study examined whether there is a link between the toxic effects of exposure to thimerosal-containing vaccines and the risk of developing ASD. The study revealed that administration of a thimerosal-containing Diphtheria-Tetanus-acellular-Pertussis (DTaP) vaccine is associated with a higher risk of subsequent ASD diagnosis than administration of thimerosal-free DTaP vaccine due to exposure to organic-Hg (Geier et al., 2013).
Moreover, there is evidence suggesting that the second and the third administrations of thimerosal-containing vaccines do not increase the probability of developing some form of ASDs. The findings of the study reveal that the risk of being diagnosed with ASD after exposure to organic-Hg from two doses of thimerosal-containing vaccine is approximately equal to that of a single dose (Geier et al., 2013). However, the study was significantly limited by the lack of information on “the precise timing and cumulative doses of organic-Hg from all thimerosal-containing childhood vaccines” (Geier et al., 2013, p. 10) that could be potentially connected with adverse health outcomes. Therefore, it is necessary to examine the timing of Hg exposure and its effects in future studies.
An article written by Mrozek-Budzyn, Kieltyka and Majewsk (2010) presents the results of a study examining the connection between measles-mumps-rubella (MMR) vaccination and the increased risk of autism in children. The study was also aimed at exploring whether there is a difference in terms of the risk of being diagnosed with ASD between using MMR and a single measles vaccine (Mrozek-Budzyn et al., 2010). The subjects were observed before diagnosis and prior to the onset of first symptoms of the disease. The results of the study suggest that the risk of developing ASD for the group that was administered MMR vaccinations was significantly lower than for the nonvaccinated group (Mrozek-Budzyn et al., 2010).
The similar connection existed between nonvaccinated children and those that were administered a single measles vaccine. The study revealed that the chances of being diagnosed with ASD after receiving a vaccination regardless of its type versus not being administered a vaccination is 0.28 (Mrozek-Budzyn et al., 2010). The findings of the study conducted by Mrozek-Budzyn et al. are confirmed by a report on the “association of the pharmaceutical preservative thimerosal and other mercury exposures” with the increased risk of developing ASD (Schultz, 2010, p187). The report suggests that the link between any form of mercury exposure and autistic disorder is tenuous. However, taking into consideration that timing of Hg exposure was not considered in the study conducted by Geier et al. and the fact that there is a chance that immunologic stimulation caused by vaccines containing antigens could be accountable for the development of ASD during the first years of life, it is necessary to conduct more research on the issue (DeStefano, 2013).
References
DeStefano, F., Price, C., & Weintraub, E. (2013). Increasing exposure to antibody-stimulating proteins and polysaccharides in vaccines is not associated with risk of autism. The Journal of Pediatrics, 163(2), 561-567.
Freed, G., Clark, S., Butchart, A., Singer, D., & Davis, M. (2010). Parental vaccine safety concerns in 2009. Pediatrics, 125(4), 654-659.
Geier, D., Hooker, B., Kern, J., King, P., & Geier, M. (2013). A two-phase study evaluating the relationship between thimerosal-containing vaccine administration and the risk for an autism spectrum disorder diagnosis in the United States. Neurodegener, 2(1), 2-12.
Mrozek-Budzyn, D., Kieltyka, A., & Majewsk, R. (2010). Lack of association between measles-mumps-rubella vaccination and autism in children: a case-control study. The Pediatric Infectious Disease Journal, 29(4), 397-400.
Price, C., Thompson, W., Goodson, B., Weintraub, E., Croen, L.,…Hinrichsen, V. (2010). Prenatal and infant exposure to thimerosal from vaccines and immunoglobulins and risk of autism. Pediatrics, 126(4), 656-664.
Schultz, S. (2010). Does thimerosal or other mercury exposure increase the risk for autism? Acta Neurobial Experimentalis, 70(1): 187-195.