Vaccines and numbers introduces a new child to the world. One more. Addition. A starting point for maths. We introduced big numbers like the over 7 billion (7*10^9 or 7,000,000,000) people who live on our planet. All of us members of a family that emerged some two hundred thousand (200,000 or 2*10^6) years ago from the Rift Valley in East Africa.
A child born today benefits from life-saving tools. Vaccines, antibiotics, clean water protect children from infection caused by bugs. We now have vaccines against more and more bugs. In New Zealand, children are given vaccines against at least 12 families of bugs. But what are bugs?
The germ theory of disease introduces you to the idea of bugs. These are microscopic (tiny) creatures that are too small to be seen by the naked eye. Some are too small to be seen in normal microscopes. These many kinds of life forms include viruses and bacteria, the two main kins of bugs that vaccines protect against.
Surprising fact: some people do not believe or understand germ theory. Surprisingly many are not even exposed to the idea; their only teaching being religious. Surprising, because the evidence has been so strong since Pasteur developed the theory in the late 19th century (1880s). Today, the evidence is even stronger as we learn about new kinds of bugs, including the Archaea that did not even exist as a separate kingdom of life when I was at school. And we now have anti-cancer vaccines as we have found the viruses responsible for liver, cervical, and other cancers.
For me, the idea for Vaccine Logic came from decades dealing with anti-vaccine arguments, prompted by doing a logic course. A lot of science is needed to understand vaccines. To learn about vaccines requires understanding many disciplines of the science of our human bodies: medicine, physiology, immunology.
Our cells of immunity protect us from bugs. But our relation with bugs is more complex than a simple war, and may be better thought of as an interplay of another level of our existence; in the same way as we can think of the interplay between the
- subatomic quarks and electrons that make up all matter
- molecule machinery of our cells
- different organs and systems that create our existence and consciousness.
- individuals who make up a family
- communities of households and families
- corporations and nations; religions
- Gaia, the planetary entity; an almost closed environmental system that has been brewing life for at least 3.8 of its 4.5 billion year life.
Each level can provide some insight to the level above it or below it. For example, the electron dance from the orbit of one atom to that of another, as they seek to find a new partner. Electrons always want to spin in pairs.
Chemical reactions involve bumping an electron off to break up and then create a new molecule by shifting the bonds, the shared electrons between the atoms. This idea helped me understand chemical reactions – but not how to learn about the specific biochemical reactions. Different domains behave by distinct laws. The social is more plastic.
We do not have the mental machinery to be able to model the quantum world. Why do think we can understand the increasingly complex social one?
Can electron behaviour provide insight into social dynamics? Humans too seem to need to pair; and to be in society. So, while we don’t need to traverse all the sciences to explain vaccines, perhaps the journey will be more satisfying.
From simple atomic processes, the chemistry of life and the shapes of immunology. To the behaviour of human individuals and populations. It does not matter how effective a vaccine is, unless it is taken up by enough of the population to prevent spread in the community. The impact of vaccines demands population coverage.
With the exception of tetanus, vaccines prevent diseases that are spread person-to-person. While the protection from a vaccine is to the individual, the impact depends on community coverage. For some vaccines, when coverage is high enough, the bug will become unable to pass form person-to-person. This is the ‘herd immunity’ threshold.
The concept of herd immunity is another one that seems to challenge people. It can be described as derived from a number, that we call R0 (R zero). The herd immunity threshold is 1 – 1/R0 (one minus the inverse of R zero). R0 is the average number of people an infected person will pass the disease onto. Measles has one of the highest know R0, estimated to be between 12-18 in most settings, so the herd immunity threshold is 92-94% immunity. As no vaccine is 100%, but two doses of measles vaccine give about 99% protection, immunisation coverage needs to be about 95% to prevent spread.
We will then take a diversion to reflect on what is happening with measles in New Zealand as we get close to this level of immunity, before starting to address the various anti-vax arguments, and from this to learn about the different types of logical flaws. Here we need to be very careful, as it is surprisingly easy to be trapped by faulty logic.
With that caution, we can then look further at the individual versus population view of the risks and benefits of immunisation. Through this to see if we can test and strengthen the logical proof that vaccination is an act of love for others, in addition to ours.
Please let me know if you have some other suggestions.