How fear is making people sick: decreasing herd immunity.
Preventable diseases such as whooping cough and measles are more prevalent now than they have been in many years. Most of these outbreaks occur in places where vaccination levels are low. What does this mean for the global population, both vaccinated and unvaccinated?
How vaccines work
The simple version goes like this: Most vaccines contain part of or a weakened form of a pathogen, which is a disease causing agent. When the pathogen enters your body, the immune system begins mounting an immune response against it. This way, the next time you encounter the same pathogen, your body can fight it faster and more efficiently, so you won’t get sick, or will be less sick. Some immunizations offer lifetime protection, while others require boosters to be effective. Several vaccines have been so successful that diseases have been eliminated in parts of the world; the most well known of these may be the polio vaccine.
Individual immunizations can prevent a person from falling ill; large-scale immunization of populations is required to eradicate a disease. So far, only smallpox has been eradicated worldwide. The last case of smallpox was reported in 1977. Several human diseases have been massively reduced by vaccines, including diphtheria, tetanus, yellow fever, polio, whooping cough, and measles. Polio was eliminated in the Americas in 1994, and in Europe in 2002, although it is still found in Asia and Africa.
Herd immunity is a form of protection in which people who are immunized against a sickness may help indirectly protect those who are not immunized. Vaccination makes individuals less likely to contract and transmit illnesses than those who are unvaccinated. As the percentage of the population that is vaccinated becomes larger, the chance of transmitting contagious illnesses decreases. Herd immunity is compromised when vaccinations are unavailable or refused by a portion of the population.
Why are cases of measles and whooping cough on the rise?
This year in the United States, there has been a 24% increase in the number of cases of whooping cough. In California and Alabama, there have been more cases in the first half of 2014 than were reported in all of 2013. The worst whooping cough outbreak in fifty years occurred in California in 2010. The outbreak was tied back to children whose parents applied for vaccination exemptions, and more instances of whooping cough appeared among non-vaccinated than vaccinated kids. In the first four months of this year, the US reported the most measles cases in eighteen years, with large outbreaks in Ohio and Massachusetts. Some have been tied back to international travelers who were exposed to measles in the Philippines. It’s worth noting that the largest Ohio outbreak occurred among the Amish population, where many children are not immunized. This map shows the global resurgence of vaccine-preventable diseases over the last six years.
Why are people refusing to be vaccinated?
In 1998, Andrew Wakefield published an article in The Lancet linking the measles vaccine to a higher chance of developing autism. The article was later retracted and Wakefield discredited when other scientists could not confirm or replicate his findings. Despite numerous assurances by doctors, the Centers for Disease Control, and most science and health care experts, people remain fearful of routine immunizations. The diagnosis of autism spectrum disorders (ASD) has risen exponentially, with a current incidence of 1 in 68 children in the US. This is a 30% increase over just two years ago. Part of this may be because the definition of ASD has changed over the years, and awareness has also improved, so more children are being diagnosed than were previously.
Although a link between vaccines and autism has been sought repeatedly since Wakefield’s accusation, no one has been able to find one. This begs the question: why are those who are anti-vaccine so sure they’re doing the best thing for their health? Surprisingly, it’s not those who are less educated or less wealthy who are participating in this movement. People with less access to healthcare tend to be undervaccinated (meaning they may not have received all the recommended doses of a vaccine), while unvaccinated children tend to have wealthy, well-educated parents who reject immunizations. It’s not a lack of information that leads to these choices; it’s a plethora of information from multiple sources. Social networks (people, not just media) play an important role in supporting the decision to oppose vaccination.
To the best of my knowledge, there hasn’t been a credible study published looking at rates of autism or other diseases in vaccinated vs. unvaccinated children. What is known is that the rates of preventable diseases are much higher among unvaccinated people. Parents will have to decide for themselves which they would rather risk.
Foxnews, NPR, Healthline, Unicef, Washington Post, CNN (Polio), CNN (autism), Chicago Mag
John TJ, & Samuel R (2000). Herd immunity and herd effect: new insights and definitions. European journal of epidemiology, 16 (7), 601-6 PMID: 11078115