vaccines’ safety
Introduction
There is significant apprehension about vaccines’ safety despite their widespread effects of protecting the public’s health. Some of these concerns are valid since no vaccine is flawlessly safe (Rare cases of paralytic polio have been reported following the administration of the oral polio vaccine, and cases of anaphylaxis have also been reported following the administration of vaccines), or effective. The Immunization Safety Review Committee was founded as an independent and proficient group by the Institute of Medicine (IOM) to analyze probable cause-and-effect linkages between immunizations and certain noxious outcomes. This committee was tasked with evaluating at least three vaccination safety hypotheses nominated by the Interagency Vaccine Group (IAVG) each year during the period 2001-2003 and have since published seven preceding reports on immunization safety matters. Their eighth and final report deals with the hypothesis that the MMR vaccine and Thimerosal-containing vaccines cause autism. An open scientific meeting was held for the assessment of queries regarding vaccines and autism by the committee in February 2004. It is important to note that the committee’s appraisals begin from the point of neutrality (Institute of Medicine (U.S.) Immunization Safety Review Committee.).
Summary of the document being reviewed
The Immunization Safety Review Committee’s eighth report analyzes the theory that some vaccines (MMR and Thimerosal-containing vaccines) are causative links for pervasive developmental disorders (PDDs), including autism. The committee’s findings are based on the examination of potential biological mechanisms and substantial promulgated and un-promulgated research conducted in the U.S., the U.K., Denmark, Finland, Japan, and Sweden. The committee came to a final determination that the available epidemiological literature supports the disapproval of the presence of a cause-and-effect relationship between the MMR vaccine and autism. The committee also determined that the available epidemiological research supports the disapproval of a cause-and-effect link between Thimerosal-containing vaccines and autism. The committee additionally holds that the available literature regarding the potential biological mechanisms for vaccine-induced autism is purely abstract. Following these findings, the committee discourages policy audit and reappraisal regarding the present-day immunization schedule and recommendations for the disbursement of the MMR vaccine or Thimerosal-containing vaccines. The committee advocates for a public health acknowledgment that wholesomely braces a collection of vaccine safety events. Moreover, the committee suggests that available financing for autism research be directed to profoundly beneficial areas (Institute of Medicine (U.S.) Immunization Safety Review Committee.).
Thesis statement: There is no cause-and-effect relationship between the MMR vaccine and Thimerosal-containing vaccines and autism.
The IOM has published two prior reports describing the possible correlation between vaccines and autism. Findings from their first report supported the disapproval of the existence of a causal relationship between the MMR vaccine and autism. However, this conclusion did not rule out that the MMR vaccine could cause autism in a small sub-group of genetically predisposed children. The committee’s second report showed inconclusive evidence to either approve or disprove the existence of a causal relationship between Thimerosal-containing vaccines and neurodevelopmental disorders of autism, attention-deficit/hyperactivity disorder, and speech or language delay (Institute of Medicine (U.S.) Immunization Safety Review Committee.).
Thimerosal is an organic mercury compound that is either utilized as a preservative in some vaccines and other pharmaceutical products or as an inactivating (bacteriostatic) agent during the production of some vaccines. Prenatal exposure to methylmercury, which is closely related to the mercury used in TCVs, has been shown to affect early childhood development adversely. Its extensive utilization in vaccines previously led to infants receiving cumulatively higher doses of mercury than the upper limits (calculated for each body-weight category) recommended by the Environmental Protection Agency (EPA), the Agency for Toxic Substance and Disease Registry (ATSDR), the FDA, and the World Health Organization (WHO). The American Academy of Pediatrics (AAP) and the United States Public Health Service (USPHS) have since recommended the cessation of Thimerosal use as a preservative and made some alterations to the immunization schedule which has resulted to significantly lower cumulative mercury exposure for children (Institute of Medicine (U.S.) Immunization Safety Review Committee.). The MMR vaccine consists of three live-attenuated viruses. The wild-type measles affects the central nervous system, and maternal rubella infection has been shown to cause congenital CNS defects. It has therefore been hypothesized that the MMR vaccine can cause neurologic disorders given that it is essentially live though attenuated viruses (Institute of Medicine (U.S.) Immunization Safety Review Committee.).
The committee carried out a scientific assessment of causality between TCVs and autism. Analysis of records from the Vaccine Adverse Events Reporting System revealed that they suffered from analytic limitations, which led to their discrediting as informative on the issue of causality. Controlled observational studies in Denmark demonstrated the absence of a causal relationship between TCVs and autism. There was no suggestion of a dose-response relationship between the amount of mercury ingested through Thimerosal. A similar study by the Vaccine Safety Datalink showed no association between TCVs and autism. Ecological studies carried out in Denmark and Sweden did not support the causal relationship between TCVs and autism. Additionally, their ecological nature limited their contributions to causality. An ecological study and studies of passive reporting data carried out in the U.S. were inherently flawed due to the presence of methodological limitations. The committee, therefore, deemed this study uninterpretable and noncontributory to causality. An unpublished Controlled Observational Study carried out in the U.K. showed that exposure to TCVs did not increase the risk of autism. An unpublished ecological study in the U.S., however, had findings consistent with the cause-and-effect nature of mercury exposure and autism. Its ecological nature limited the study’s contribution to causality (positive ecological correspondence amounts to weak evidence of causality). Based on this literature, the committee concluded that there was no cause-and-effect relationship between TCVs and autism (Institute of Medicine (U.S.) Immunization Safety Review Committee.). I agree with this conclusion because the evidence supporting the hypothesis that TCV directly causes autism is weak. The epidemiological studies invariably showed no association between TCVs and autism.
Assessment of causality between MMR vaccine and autism involved the evaluation of sixteen epidemiological studies carried out in the U.S., the U.K., Denmark, Finland, and Sweden. Controlled Observational Studies conducted in the U.S., the U.K., Denmark, and Finland demonstrated the absence of a causal relationship between MMR vaccine and autism with a case-control study in Japan showing a decreased risk of developing autism following the administration of MMR as opposed to the monovalent variants of the vaccines. Ecological studies carried out in the U.S., the U.K., and Sweden also demonstrated the absence of a causal relationship between MMR vaccine and autism. Reviews of Passive Reporting Data carried out in the U.S. and Finland were noncontributory to causality and limited in contribution to causality, respectively. Based on this literature, the committee concluded that there was no cause-and-effect relationship between MMR vaccine and autism (Institute of Medicine (U.S.) Immunization Safety Review Committee.). I agree with this conclusion. The evidence supporting the rejection of this hypothesis is overwhelming and is consistent with the committee’s prior publication on MMR and autism.
The committee also analyzed biological mechanisms that had been hypothesized as links between vaccine components and autism. The hypothesis examined by the committee was that vaccine-induced autism is the outcome of genetic susceptibility to immune dysfunction or impaired mercury metabolism. The committee, however, noted various aspects that hinder the acceptance of this hypothesis: other contexture exposures could have comparable effects, the elaboration of an in vitro outcome cannot readily equate to a physiological argument, and there was no theory explaining why vaccination was the only environmental exposure leading to autism and therefore concluded that the insufficiency of experimental or human evidence that vaccines alter body physiology leading to autism renders this hypothesis purely abstract (Institute of Medicine (U.S.) Immunization Safety Review Committee.). I also agree with this conclusion. This is because the evidence put forward in support of this theory consists of data from laboratory investigations and correspondences between rodent and human behavior, which can, in the very least, be explained as being coexistent disease manifestations rather than causal factors.
Conclusion
Conclusive evidence supporting the existence of a cause-and-effect relationship between the administration of MMR vaccines, TCVs and autism is yet to be published. Immunization is, therefore, considered to be safe and should be encouraged. The benefits of immunization have been widely recorded, and immunization is universally appreciated as a tool for protecting the public’s overall health.
Works Cited
Institute of Medicine (U.S.) Immunization Safety Review Committee. Immunization Safety Review: Vaccines and Autism. Washington, DC: National Academies Press (U.S.), 2004. Website: https://www.ncbi.nlm.nih.gov/books/NBK25349/#_ncbi_dlg_citbx_NBK25349.