The vaccination process

In rich countries, few children die of rotavirus diarrheal disease, but it does kill some 500,000 kids living in poor countries annually. Prior to 2006, when vaccines against rotavirus became available, about one in five kids under the age of five in the United States annually came down with it, of which 57,000 were hospitalized. Subsequent to widespread vaccination, hospitalization rates have dropped by 90 percent. Interestingly, rotavirus hospitalizations among older children and young adults who are not immunized have also fallen by around 10,000 annually. Why? Because they are no longer are exposed to the disease in infants who would otherwise have infected them.

Vaccines do not produce immunity in some people, so a percentage of those who took the responsibility to be vaccinated remain vulnerable. This brings us to the important issue of herd immunity. Herd immunity works when most people are immunized against an illness, greatly reducing the chances that an infected person can pass his microbes along to other susceptible people, such as infants who cannot yet be vaccinated, immunocompromised individuals, or folks who have refused the protection of vaccination.

People who refuse vaccination for themselves and their children are free-riding off herd immunity. Anti-vaccination folks are taking advantage of the fact that most people around them have chosen the minimal risk of vaccination, thus acting as a firewall protecting them from disease. But if enough refuse, the firewall comes down and other people get hurt.

Oliver Wendell Holmes articulated a good libertarian principle when he said, "The right to swing my fist ends where the other man's nose begins." Holmes’ observation is particularly salient in the case of whooping cough shots.

Infants cannot be vaccinated against whooping cough, so their protection against this dangerous disease depends upon the fact that most of the rest of us are immunized against it. Unfortunately, whooping cough incidence rates have been increasing along with the number of people refusing immunization for their kids. The annual number of pertussis cases fell to a low of 1,010 in 1976. Last year, the number of reported cases rose to 48,277, the highest number since 1955. Eighteen infants died of the disease in 2012, and half of the infants who got it were hospitalized.

In 2005, an intentionally unvaccinated 17-year-old girl brought measles back with her from a visit to Romania and ended up infecting 34 people. Most of them were also intentionally unvaccinated, but a medical technician who had been vaccinated caught the disease as well and was hospitalized. Despite the medical technician’s bad luck, the good news is that the measles vaccine is thought to protect 99.8 percent of who get the shot. Similarly, in 2008 an intentionally unvaccinated seven-year-old boy sparked an outbreak of measles in San Diego. The boy, who caught the disease in Switzerland, ended up spreading his illness to 11 other children, all of whom were also unvaccinated, putting one infant in the hospital. Forty-eight other kids who were too young to be vaccinated were quarantined.

To borrow Holmes’ metaphor, people who refuse vaccination are asserting that they have a right to “swing” their microbes at other people. There is no principled libertarian case for their free-riding refusal to take responsibility for their own microbes.