As should be obvious to regular sciblogs readers, this is Vaccine Awareness Week.
Rather than focus on anti-vaccine views, I’d like to present a few links with commentary as some sort of starting point to encourage reading about vaccines, mainly focusing on the origins of the idea of vaccination and a very brief conceptual outline of the basis of more modern vaccines.
If current-day information is your interest, you are best to visit one of the sites listed in my Sources for medical information for non-medics and non-scientists.
The detailed history of the development of the modern vaccine is a very long and complex story, one I am not going to relate here. My focus is on the basic conceptual principles.
One source for the story of the development of modern vaccines might be Arthur Allen’s book Vaccine. (See cover to left. This book is focused on developments in the USA.)
The idea of inoculation is surprisingly old.
Various sources will tell you it originated in different locations in the world sometime BCE. (These accounts also illustrate how Eurocentric accounts can exclude earlier events elsewhere.)
A basic theme is that of observing that those that survived (a modest) infection seemed to not suffer it again: they gained protection somehow. From these observations people seemed have adopted simple procedures to deliberately introduce small infections in their young.
If you leave aside his opening remarks about bioterrorism, one good read is Stefan Riedal’s brief history of inoculation, focusing on smallpox vaccination. Don’t be put off by the formal source – it reads more as popular science history rather than formal research literature.
Historically, cutaneous leishmaniasis has been the focus of vaccination attempts, probably because it has been known since antiquity that individuals who had healed their skin lesions were protected from further infections. Bedouin or some Kurdistani tribal societies traditionally expose their babies’ bottoms to sandfly bites in order to protect them from facial lesions. Another ancient technique practised in the Middle East has been the use of a thorn to transfer infectious material from lesions to uninfected individuals.
[Source: review of leishmania and leishmania vaccines, 2001, more formal but generally readable; open access.]
A well-illustrated informal history of vaccination can be found on Adam Blatner’s website.
For both cowpox and leishmania inoculation, the concept is of introducing a small, somewhat controlled, infection that will hopefully induce immunity by placing some of the pus from a wound from an infected person on the uninfected person.
While simple in concept, direct inoculation like this also carried risk.
In introducing infection from a wound from another person, there is the risk of spreading other diseases. There is also the risk of creating a carrier infection, which will go on to cause the full disease in others. Some of the inoculated themselves might contract the disease and suffer the consequences.
You can think of vaccination as a refined form of inoculation that tries to avoid the risks associated with crude inoculation of pus from a wound (or the like).
You’ll have heard of how the first smallpox vaccine was developed, how Edward Jenner tested the idea that cow maids who got cowpox didn’t get smallpox by infecting a boy, James Phillip, with a cowpox from a cow maid, Sarah, then later testing James’ reaction to a smallpox inoculation. Jenner developed this into a cowpox vaccination to prevent smallpox infection, put this on a sounder basis and popularised the concept. The original idea didn’t start with him – history predates the basic concept – but he did put it on a better basis and encouraged vaccination of communities.
The word ‘vaccine’ comes from the Latin for cow, vacca.
The history of anti-vaccine movements stems from Jenner’s day, too, with objections from various angles. Some dismissed the notion that disease from one animal could protect humans. Although unsound now, you can at least appreciate this in the context of what was known then. (Or, rather, what was not known.)
Poorly administered trials of Jenner’s idea caused, rather than prevented, smallpox. Unsurprisingly this caused concerns over introducing disease, not preventing it.
Some religious groups – the original ‘anti-vaccinationists’ – objected too. Some of these religious people apparently considered the notion of being ‘infected’ by a ‘lower’ animal abhorrent. Today we are well aware that we have bacteria on and within us, and that our genomes contain relics of ancient viral infections.
The anti-vaccine ’movement’ is not new or founded on modern fears, but started from these earlier beginnings with objections no-one would now raise. You can view this opposition as the cycle of whispers I mentioned at the onset on a longer time scale, with new twists on the old themes.
But let’s get back to the story.
Vaccinating with cowpox, rather than inoculating with smallpox reduced the risk – cowpox was known not to cause serious infection in humans, but could be used to as the basis of preventing a more serious infection.
Modern vaccines carry the aim of reducing risk further.
A key element to the development of modern vaccines is that they build on research in biochemistry and molecular biology – areas of science not present in Jenner’s day – that have shown that the protection is derived from an immune system ‘memory’ of macromolecules that are part of the infectious organism (virus, bacteria).
When something foreign is found in the body, the immune system identifies it and makes cells that specifically recognise the foreign thing and destroys it. If the same person is later exposed to the same foreign thing, the body can react quicker using the reservoir of progenitor cells that generate the cells that destroy the particular foreign thing.
The aim in making a vaccine is to present to the immune system something that will cause it to create cells that will be effective against the actual organism, even if the vaccine isn’t the organism itself.
Recognising this, something that could only be realised with biochemistry and molecular biology – science not present in Jenner’s day, has allowed the development of a number of ways of making safer vaccines (including inactivated, attenuated, virus-like particle and subunit vaccines, along with some more recent developments).
Subunit vaccines, for example, use molecules from the surface of the organism (virus, bacteria) that the immune system recognises both on their own and in the full organism. Since these molecules are not living, they cannot cause an infection.
Adjuvants are another aid in making vaccines more effective. Aside from strengthening the immune response adjuvants allow smaller amounts of the immunogenic material to be given.
I’m going to leave you with this. I hope that this might be enough to encourage readers on take this further themselves.
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