Vaccines are among the greatest medical achievements in human history. They are responsible for eradicating smallpox and eliminating several diseases, including polio, diphtheria and measles, from large regions of the world. Despite impressive effect against many infectious diseases, including measles, vaccines remain controversial. Reports of vaccine-related side effects often receive considerable attention in the media and cause many adults to refrain from vaccinating themselves or their children. Unvaccinated individuals can help diseases spread, a contributing factor to the large outbreak of measles in Disneyland, 2015.
During the outbreak, 45% of 110 Californian patients were unvaccinated and another 43% had undocumented vaccination status. In order to maintain the herd immunity which reduces disease transmission and protects vulnerable individuals in the society, vaccination against highly-infectious diseases must be mandatory.
Vaccination provides a strong protection against disease. They are made to trigger a specialized immune response by imitating infection caused by specific disease-causing organisms, such as various virus and bacteria. Once the immune system produces antibodies against the vaccine components, it can respond rapidly to subsequent infections by the "real organism" and the individual becomes immunized. Immunized individuals are protected against disease caused by infection and immunization may even prevent infection itself. This protection only applies to the person who receives the vaccine and has an effective immune response.
However, vaccines can also prevent disease through a mechanism known as ‘herd immunity’ (Fine, Eames & Heymann, 2011). Herd immunity is obtained once a high proportion of the population is immunized against a disease; the protective proportion is known as the herd immunity threshold (Fine, Eames & Heymann, 2011). When a population reaches the threshold, diseases can no longer spread effectively within communities.
The herd immunity is crucial for effective vaccination, as it provides indirect protection against diseases for people who may be too young or too sick to receive the vaccine. For example, twelve of the 110 Californian patients of the measles outbreak in Disneyland were children too young to be vaccinated (Zipprich et al., 2015). Many of these children could have been protected from the disease through herd immunity if the number of vaccinated individuals was higher during the outbreak.
Misinformation surrounds vaccines and makes attempts to enforce vaccination difficult. Andrew Wakefield, a British gastroenterologist, published a famous article in 1998 where he associated the MMR vaccine (mumps, measles and rubella) with autism development in children. Many parents felt they had been deceived by the scientist community and vaccination rates declined. 22 independent research papers from around the world since reviewed the research and disproved Wakefield’s claims. It is clear that misinformation can cause public distrust and consequently loss of herd immunity.
However, side effects caused by vaccines are no myth. The MMR vaccine, although no longer associated with autism, has reports of bleeding disorder in 1 out of 30,000 doses and seizures in 1 out of 3,000 doses (“Vaccine Information Statement”, 2012). Many members of anti-vaccine movements argue that mandatory vaccination is unethical as long as there is a risk of serious side effects. In the context of vaccination it is, however, important to consider the risk associated with the diseases they can prevent. Not only in terms of physical, short-term risk, but also economical, social and long-term consequences of certain infections.
Measles, one of the three diseases preventable through MMR vaccination, has a case-fatality rate of 3 out of 1000 reported cases even in developed countries. Highly infectious diseases have a much higher impact on the society than any disease against them.
Additionally, side effects are more likely to occur in individuals that are predisposed by age or chronic disease. These individuals can be protected from disease through the herd immunity if all otherwise healthy individuals are vaccinated. It is equally, if not more unethical to allow preventable diseases to endanger the most vulnerable individuals in our society.
Vaccination is not only a matter of individual health, but of greater public health. In a time of global travel and immigration, diseases can reappear unexpectedly and government health programs must ensure that the population is protected. Mandatory vaccination against highly infectious diseases secures herd immunity, while few exceptions are reserved to vulnerable individuals who cannot receive vaccines due to health concerns. With strong herd immunity, outbreaks that cause unnecessary mortality and large economic costs can be avoided. If misinformation continues to persuade a minority of the people to refuse vaccination, mandatory vaccination might be the only option to prevent future outbreaks.