Vaccine Safety: risk communication

Introduction

This article evaluates four different risk factors, collectively labelled a "complex of risk", that are associated with vaccine-preventable diseases and the vaccines designed to prevent them. The author reviews the available data and case examples pertaining to disease and immunisation risk and places them in a framework for assessment with the goal of providing insight into improving risk communications, and preventing damage to current and future immunisation programmes. The author concludes by arguing that more research into the actual risks of vaccination must be matched with robust communication strategies that take into account the factors she has identified.

Key Findings

The author identifies a "complex of risk", a set of factors that must be evaluated when attempting to assess the level of vaccine risk. The first component of the complex is the risk of vaccine-preventable diseases and risk reduction through immunisation. In 1998, infectious diseases were the number two cause of death globally - behind cardiovascular diseases - and accounted for 25% of global deaths. They are also the world's biggest killer of children and young adults. The benefits of immunisation programmes have become widely recognised since the initiation of the World Health Organization (WHO's) Expanded Programme on Immunisation (EPI) in 1974, which has prevented the deaths of some 3-4 million children. Furthermore, adverse reaction risks from vaccines such as those for measles have been shown to be far lower than the risk for complications. The risk of refusing or interrupting immunisation programmes is also obvious and the author provides examples of outbreaks of pertussis (Japan, UK), polio (Netherlands, Albania), and diphtheria (Newly Independent States) following immunisation interruption.

The second factor in the complex of risk is the true, perceived, and unknown risks connected with immunisation. The author notes that adverse events, both those that are causally related and those that are merely temporal, become more visible than natural disease. Vaccines have helped to make many of these diseases invisible while bringing attention to their own shortcomings (side effects). The data pertaining to adverse reactions however, is as yet incomplete, despite a growing focus on safety. The author proceeds to provide a summary of the current knowledge of complications that have been associated with specific vaccines. There is also the continuing issue of programmatic errors, a potentially substantial problem given the 5-10 billion injections that are administered each year. Cases of HIV and Hepatitis B infection from inadequate sterilisation and bio-safety protocols have become a major area of focus for the WHO.

The author then provides a catalogue of the perceived adverse events of immunisation that have fueled anti-vaccination campaigns and have led to difficulties with achieving higher coverage rates in some poor countries. Some of the most prominent associations include the measles/MMR vaccine and its suspected relationship to Crohn's disease (CD) and autism, the hypothesis suggesting that oral polio vaccine (OPV) was the cause of AIDS, and suspected links between various vaccines and Sudden Infant Death Syndrome (SIDS). Another component is the unknown risks - where evidence is inadequate to accept or reject a causal relation. Knowledge about vaccine risks is incomplete, as is the research capability to make definitive assessments. The author notes that the USA's Institute of Medicine (IOM) was unable to conclude for or against vaccine causality in nearly two-thirds of the cases they investigated in the early 1990s. A full understanding is hampered by limitations such as an inadequate understanding of biologic mechanisms, insufficient information from case reports, inadequate size/length of follow-up of epidemiological studies, limitations of existing surveillance systems, and few experimental studies.

The author identifies two other factors composing the "complex of risk"; the first is the avoidance of risks through requirements for good manufacturing practices, and quality control of vaccines along with appropriate licensure surveillance. The author notes that a substantial part of modern biologic safety policy emerged as the result of accidents. Most countries do not have sufficient post-licensing surveillance systems, even if they have the policy on the books, to ensure the safety of actively circulating vaccine stocks, and instead rely on passive detection. Finally the author notes that the medical and vaccination community, including insurers, manufacturers, and governments, must accept the existence of immunisation risks through the establishment of appropriate compensation schemes. This is considered to be an important sign by health authorities that they are aware of the risks and prepared to accept these outcomes, yet remain confident that the vaccination programme is in the best interest of the general populace.

The author concludes with discussion on how, given this complex of risk, damage can be avoided to current and future immunisation programmes. She suggests that there is a critical need for more complete data and that the public is aware that there is sufficient funding for continuing vaccine safety and research. Responses to adverse events must be rapid; this includes re-evaluations if the linkage is found to be correct and credible counter-messaging if health authorities believe that the connection is spurious. Some specific recommendations for ways to improve vaccine risk communications include: (1) tailoring communications to specific situations, differentiating between the general public and medical community and their interests; (2) improving the format and structure of printed materials; (3) presenting the various risks/benefits in a balanced manner - including disease risk, adverse event risk, both real and perceived; and (4) adding references and sources to allow interested parties to have full access to materials.

The author contends that these concrete suggestions - combined with the thorough and transparent presentation of the "complex of risk" model - will improve public confidence in immunisation strategies and protect vaccination programmes and the public health gains they have generated.