infectious diseases
Overview of Immunization
Vaccine Safety
In the United States, the safety of vaccines is ensured through two surveillance systems: the CDC's and the U.S. Food and Drug Administration's (FDA) Vaccine Adverse Event Reporting System (VAERS) and the Vaccine Safety Datalink (VSD). VAERS is a safety program cosponsored by the FDA and the CDC; VAERS collects reports from individual patients who believe that they had an adverse event after a recent vaccination. Health care professionals are also required to report certain events after vaccination and may report events even if they are unsure the events are vaccine-related. VAERS reports originate all across the United States and provide a rapid assessment of potential safety issues. However, VAERS reports can show only temporal associations between vaccination and the suspected adverse event; they do not prove causation. Thus, VAERS reports must be further evaluated using other methods. One such method uses the VSD, which uses data from 11 large health care organizations. The data include vaccine administration (noted in the medical record as part of routine care), as well as subsequent medical history, including adverse events. Unlike VAERS, the VSD includes data from patients who have not received a given vaccine as well as those who have. As a result, the VSD can help distinguish actual adverse events from symptoms and disorders that occurred coincidentally after vaccination and thus determine the actual incidence of adverse events. Nonetheless, many parents remain concerned about the Childhood Vaccination and their possible adverse effects (particularly autism). These concerns have led some parents to not allow their children to be given some or all of the recommended vaccines (see One of the main parental concerns is that vaccines may increase the risk of Autism Spectrum Disorders . Reasons cited include A possible connection between the combination measles-mumps-rubella vaccine and autism (see Measles-Mumps-Rubella (MMR) Vaccine ) The possibility that thimerosal might cause autism (thimerosal is a mercury-based preservative used in some vaccines—see Thimerosal and Autism ) Use of Use of Multiple, Simultaneous Vaccines , given as recommended retracted the report because it contained serious scientific flaws; many subsequent, large studies have found no evidence to support an association between use of vaccines and risk of autism ( Vaccine safety references ). The US Institute of Medicine Immunization Safety Review Committee reviewed epidemiologic studies (published and unpublished) to determine whether the measles-mumps-rubella vaccine and vaccines containing thimerosal cause autism and to identify possible biologic mechanisms for such an effect; based on the evidence, this group rejected a causal relationship between these vaccines and autism ( Some of the concerns regarding autism and childhood vaccines were regarding vaccine constituents. Thimerosal, a preservative, was the focus of some of these concerns, although the MMR vaccine never contained thimerosal. Currently, virtually every vaccine given to children in the United States is thimerosal-free. Small amounts of thimerosal continue to be used in multidose vials of influenza vaccine and in several vaccines intended for use in adults. For information about vaccines that contain low levels of thimerosal, see the Food and Drug Administration's web site (Thimerosal and Vaccines). Thimerosal is also in many vaccines used in resource-poor countries. As with any treatment, clinicians should talk to their patients about the relative risks and benefits of recommended vaccines ( Vaccine safety references ). In particular, clinicians must make sure that the parents of their patients are aware of the possible serious effects (including death) of vaccine-preventable childhood diseases such as measles, Hib infection, and pertussis, and clinicians should discuss any concerns parents may have about vaccinating their children. Resources for these discussions include the CDC's 1.Gerber JS, Offit PA: Vaccines and autism: A tale of shifting hypotheses.Clin Infect Dis48(4):456-461, 2009. doi: 10.1086/596476 2.Institute of Medicine Immunization Safety Review Committee: Immunization safety review: Vaccines and autism. Washington DC, National Academies Press, 2004. 3.Spencer JP, Trondsen Pawlowski RH, Thomas S: Vaccine adverse events: Separating myth from reality.Am Fam Physician95(12):786–794, 2017. PMID: 28671426 