August is National Immunization Awareness Month, and it’s purpose is to spread awareness and highlight the importance of immunizations throughout an individual’s life to protect not only oneself, but the health of the entire population. Certain immunizations are required as an individual grows up, and some are optional (like the yearly flu shot).
Vaccines have become controversial, but the data supporting it is not. Let’s break down three important terms to help understand how vaccines work.
Chain of disease:
Today, you can travel anywhere and bring a myriad of diseases with you; someone in Africa traveling to the U.S. can (and did) bring Ebola here. Measles, while eradicated in the U.S. in 2000, is still prevalent in other countries, which is why it is important to keep up with vaccinations in the U.S. Because of our interconnectedness, outbreaks can be more difficult to contain. In essence, our world population is one incredible, linked human “herd” that can easily spread diseases.
When most of a population is vaccinated, they break the “chain of disease.” The more vaccinated people there are, the more roadblocks are thrown up to stop the disease’s ability to pass from person to person — and this not only allows infants and people with weakened immune systems more protection, but also adds even more protection for those who are vaccinated or have contracted the disease before. Herd immunity allows the strength and protection of the whole community to slow or stop the spread of disease from person to person; however, herd immunity depends on each disease’s threshold.
Threshold is the minimum percentage of immune people that a community needs to prevent an outbreak. The microbes that cause diseases have different infectious features (such as ease of transmission, and severity) and the risks can shift as a person ages. Infants have a much higher risk of dying from whooping cough than adults, for example.
Creating a threshold is complex and depends on factors like these:
- Basic reproductive rate (“R0”) is a number that represents how many people in an unprotected population that can contract the disease from one infected person. For example, measles has a Ro of 12-18, while mumps has a R0 of 4-7.
- How effective the vaccine is for a given disease.
- How long the immunity lasts, from both vaccination and infection.
- Which populations form critical links in transmission of the disease.
Outbreaks have been on the rise in recent years because of a fear that vaccinations cause other conditions, like autism. As with all medications, they do run the risk of mild side effects, but very rarely have severe side effects. If someone has a weakened immune system or a disease like cancer, they should not get the vaccine — but that makes it that much more important for healthy people to get vaccines, so they can offer that herd immunity.
Watch this video to learn more about vaccines. (And go here to learn more about the studies disproving the most commonly cited myth about vaccines.)