Vaccines are considered the greatest public health achievement of the 20th century by the Centers for Disease Control and Prevention [4]. Even so, they have recently come under scrutiny by the media and a vocal minority of concerned parents. A large number of parents are wary of combination vaccines because of negative publicity focusing on possible side effects, including autism. Although many of these reports lack scientific evidence or describe rare occurrences, they are nonetheless influential in parents’ decision-making processes. A common charge is that combination vaccines overload the young child's immune system, leaving him or her more susceptible to other infections [31]. Some parents see this as a case for single-antigen vaccines. However, parents also worry about the pain their children experience when receiving multiple injections at a single office visit. This can lead them to delay or refuse vaccinations, leaving their children and other children who are medically unable to receive vaccines unprotected. With new vaccines continually being developed, it is important to understand and attempt to allay parents’ fears so that their children can be protected from potentially deadly diseases. Although many other factors influence parental attitudes toward vaccines, this literature review synthesizes research on these two specific fears to determine how parents choose between combination and single antigen vaccines.
As more parents refuse or delay immunizations for their children, the herd immunity protecting vaccine non-responders and the unimmunized, including those who are immunocompromised or too young to be vaccinated, decreases. Besides the risk to the children, the decision not to vaccinate also places stress upon pediatric practices. They must balance the liability of an unvaccinated child – the possibility of infecting others in the waiting room or other setting, injury resulting from vaccine-preventable disease, or allegations of failure to adequately educate caregivers about the risks of vaccine-preventable disease – with the similarly undesirable option of dismissing the family from the practice [28].
Many parents today have never experienced deadly vaccine-preventable diseases and may underestimate the diseases’ severity [9]. The United States has seen several recent outbreaks of diseases that were once under control in this country, like pertussis and measles [1] and [18], and the increase in global travel places everyone at risk.
An increase in the number of vaccines on the CDC immunization schedule over recent years has resulted in five or more separate injections being given during a single office visit [5]. In an attempt to simplify the schedule, a diphtheria–tetanus–whole-cell pertussis vaccine came into use in the 1940s and now more than 20 combination vaccines are in use or under development [16]. While combination vaccines have numerous benefits, in a 1998 article the MMR (measles–mumps–rubella) vaccine was reported to have been linked to autism and inflammatory bowel disorders [35]. Although the study was later found to be fraudulent and the author's medical license was revoked due to multiple breaches of ethical principles [12], people continue to fear the side effects of combination vaccines.