One short thought turns into epic ramble
I am a scientist. Or rather, I am a PhD student in training to be a scientist[1]. Either way, I love science, and I love reading and talking about it, so I thought I’d try writing about it.
Having recently two excellent book offerings from Paul Offit[2],
an American paediatrician and Professor of Vaccinology, shortly
followed by the recent publication of journalist Brian Deer’s damning
three-part exposé into the Wakefield saga[3],
I’ve been thinking about vaccination a fair bit lately, hence my choice
to write a piece about them. However, unlike a great deal of the
reporting of vaccines that we’ve been bombarded with over the last two
decades, I shall be weighting my article based on the credible, reliable
and repeatable evidence that we have available. As such, I shan’t be
pandering to the false dichotomy of vaccines vs. autism (or any other
number of perceived pathologies) set up by rogue scientists,
questionable personal injury lawyers, irresponsible or impressionable
reporters and celebrities (which unfortunately is often then absorbed by
anxious and misled parents)[4].
Instead, I am going to try to illustrate why vaccines are one of the
greatest forces for good that humanity possesses, and why it’s so
important that people care about them.
Hands up if you know anyone with smallpox. No? Anyone? Of course not. That’s because vaccines are
literally awesome, and no-one has smallpox anymore[5].
Vaccines work by making use of our immune systems; in particular,
the branch of these systems that we call the adaptive immune system.
Adaptive immunity has evolved as a way for large, complex organisms
(like us) to resist the parasitic advances of smaller, pathogenic
organisms of varying complexity (such as viruses, bacteria, fungi and
eukaryotic parasites), by finding them within the body and dealing with
them. The key thing about adaptive immunity is that after encountering a
particular bug, it
remembers how it dealt with it the first time, and can then do it much better and much faster if it ever runs in to the same bug again[6].
Broadly speaking, it does this through the generation of a vast diversity of two kinds of cells. B-cells (produced in the
bone
marrow) produce antibodies, which are small proteins that bind to
foreign molecules (such as are found on the outside of infectious
agents) and either neutralises them, or flags them up as suspicious for
the second type of cell, T-cells (which mature in the
thymus).
T-cells come in two flavours, which can either kill infected cells
directly by squirting them with self-destruct proteins, or release
chemicals to orchestrate further immune responses from other cells[7].
The general concept behind vaccines is to present someone’s
adaptive immune system with either a weakened or inactivated version of a
pathogen, or even just whatever bit of the microbe that the immune
system happens to ‘see’. When we immunise someone they shouldn’t get
sick with whatever they’re being immunised against (as it’s not a
functioning, virulent agent used), but their adaptive immune system
‘remembers’ that pathogen or molecule. Then, if this person is unlucky
enough to encounter this particular bug, their immune system recognises
it from the immunisation, and makes the appropriate biological response,
clearing the infection and keeping the vaccinee healthy.
The UK currently encourages vaccination of children, and provides
free jabs for the following eleven diseases: diphtheria, tetanus,
pertussis, polio,
Haemophilus influenzae type B, pneumococcal bacteria, meningitis C, measles, mumps, rubella and human papilloma virus[8].
Thankfully, looking at the 2009 uptake of vaccinations versus the
estimated herd immunity requirement (which is the threshold of the
population that needs to be immune to protect those who lack immunity)
it seems that the diseases for which there are data surpass the lower
estimate, meaning that those diseases should not be able to take root
here[9].
However, seeing as these diseases are all but eliminated in the here
and now it is very easy for us to take our immunity for granted, and
forget what horrible sickness these pathogens cause. So, to keep things
fresh in your mind, I’ll just run down a few of the delightfully
horrible symptoms, complications, and possible outcomes of these
conditions.
As with a great many infections, most of these diseases start off
soft, with general, make-you-feel-rubbish symptoms, causing fatigue,
malaise, nausea, coughs, sneezes, and fevers both high and low. They
might hit different parts of the body, with running noses, sore throats,
aching heads, chests, neck, ear infections, bull necks, genital warts,
or locked-jaws, maybe turning you blue, red, or (gan)grene along the
way. Then you reach the difficulties; difficulty breathing, swallowing,
going to the toilet,
not going to the toilet, or even remaining
conscious. By now we're up to the big boys of complications.
Meningitis. Bacteremia or septicaemia. Blindness and deafness. Partial
or complete paralysis. Encephalitis. Sterility. Birth defects and
spontaneous abortions. Oh, and don't forget the death. Death from
respiratory failure, death from pneumonia, death by suffocation, death
from inflammation, death by cancer, death by chocolate and yet more
death, death, death[10].
All this morbidity, all this mortality, all this human suffering,
misery and pain, all prevented when enough of a population is vaccinated
against the pathogens that cause them.
Granted, a lot of these more severe complications may be rare
events in infected individuals, but that is not to belittle them. If a
virus or bacteria only kills 0.01% of the people it infects, it doesn’t
sound like much, that’s only one in 10,000 people. The only problem is,
there are a lot of people in the world. The UK has about 68 million
people living in it; even if only half of them get infected with this
imaginary bug, a fatality rate of 0.01% still kills 3,400 people. Before
vaccination and treatment, some of these diseases used to cause
hundreds of thousands of deaths annually, sometimes laying waste to huge
swathes of the populace. We’re lucky to live in a time and a place
where such horrific diseases can be and are prevented, but we cannot
take this for granted. Even as late as 2002, the World Health
Organisation (WHO) estimated that globally, there were as many as 2.5
million deaths worldwide from vaccine-preventable diseases, 1.4 million
of which were in children beneath the age of five[11].
It seems to me that the death of a child is one of the worst tragedies
imaginable, surpassed only by the fact that so often that life could
have been saved by a simple, safe, reliable vaccination.
Clearly, vaccines are of tremendous worth in preventing and
controlling infectious diseases. However, in an exciting twist
researchers are increasingly looking at using vaccines to solve
conditions that you might not expect.
Among more developed populations, where health care and
preventative measures are likely to be relatively strong, cancer is
probably among the most feared health conditions. Perhaps the most
insidious of all diseases, cancer involves the very cells of a person’s
body turning against them, throwing off the shackles that control
cellular growth and turning renegade, dividing uncontrollably with no
regards for the host from whence they came.
Much cancer treatment involves using drugs that non-specifically
target rapidly dividing cells (chemotherapy), which hits the cancer
cells, but also hits any other cells in your body that happen to be
dividing (such as the parent cells of the immune, gastrointestinal,
reproductive systems). Cancer vaccination works by trying to co-opt your
immune system to prevent cancer, or even treat it therapeutically.
One way in which vaccination can prevent cancer is by vaccinating against pathogens that cause or contribute to cancer[12].
If the infection that causes the cancer can’t take root, then that
cancer cannot grow either. When the cancer is not due to an infectious
agent, then a more direct approach can be taken. Patients can be
immunised with antigens[13]
that the cancer cells express, but normal healthy cells don’t, in order
to provoke an immune response specifically against the cancer, a
strategy which makes use of the fact that cancer cells often aberrantly
express proteins (or combinations of proteins) that a normal, healthy
cell wouldn’t. Alternatively, scientists have taken a craftier tactic,
where they inject people with a virus they’ve modified to exclusively
attack tumour cells; when these cells lyse (or break apart) thanks to
this oncolytic virus, their contents spill out into the tissues of the
body, providing the immune system with buckets of cancerous proteins,
effectively immunising against the cancer from within.
All the vaccines I’ve mentioned so far involve stimulating or
promoting immune response against a particular target. However, it is
also possible to make a vaccine that dampens or suppresses an existing
immune response, a technology which theoretically could be used to treat
any number of autoimmune diseases[14].
This might be achieved by targeting the immune cells that are
responsible for the disease directly, or by targeting regulatory cells
whose job it is to make sure that other cells don’t cause autoimmunity.
This avenue could offer treatments for a plethora of conditions, from
diabetes to allergies, or from MS to Alzheimer’s.
Perhaps most surprisingly, vaccines are even being considered to
fight drug addiction. That’s right, you can vaccinate against drugs.
Specifically, vaccines are in development to treat nicotine and cocaine
addictions. Both strategies work in a similar manner; the drug (or a
chemical analogue, or look-alike) is stuck to something that’s known to
stimulate an immune response. This hodgepodge molecule can then be used
to immunise an addict, who then will hopefully develop immunity against
the nicotine or cocaine. When they next spark up (or otherwise imbibe)
the theory goes that the immune response will kick in, the drugs will
get coated in antibodies and then won’t be able to carry on chilling you
out or getting you high, and the addict gets less (or no) bang for
their buck, before deciding it’s a fool’s game and throwing away their
junk[15].
Whether you agree or not that this is a good idea, it is a good
demonstration of the power of vaccination, and a good illustration of
what we might be capable of if only we have the imagination[16].
It would be remiss of me to ignore the mistakes that the field of
vaccinology has made. There have been vaccines that have been
ineffective, or – more rarely – even harmful. However, these incidents
are largely historical, and the few incidents there have been have been
thoroughly investigated so that they do not happen again[17].
It is also worth noting that the most successful vaccination strategy
ever was not without risks; the vaccinia virus vaccination that
eradicated smallpox caused serious complications in a very small
minority of people, even killing one in a million of those who received
it. However, compared to fatality rates of 20 to 60% when infected with
smallpox (or even greater than 80% in children), the risk from the
vaccine was by far the wiser choice[18].
Of course, even if we could make vaccines for all communicable
diseases, and we could get these vaccines distributed to all the corners
of the world, it would not stop these diseases in their tracks,
particularly in the developing world. Vaccines are a wonder, but – as
with all aspects of applied biology – they are not perfect, and require
functioning immune systems in order to provide immunity. In addition to
vaccination there needs to be provision of general health care and
infrastructure, clean water and adequate nutrition. Even in a well-fed
well-cared for society, where everyone who can be is vaccinated, there
is still a chance of infection, as vaccines (as with all treatments) are
not 100% effective; there will always be individuals who either are
unable to get the treatment (perhaps due to some underlying
immunodeficiency) or who fail to generate an appropriate immunological
response. This is why it’s important for everyone who
can be
vaccinated to get vaccinated; once a herd immunity threshold is met,
then there isn’t enough tinder of susceptible individuals for the flame
of infection to ignite and spread.
Vaccines aren’t the answer to solving the burden of disease. They’re
just a fantastically important part of it. We have made tremendous
advances in our understanding of life, bounding along at an exponential
rate for the last 500 years or so. However, infectious disease-immune
system interactions have had a bit of a head start in their development,
of about 3 billion years[19].
We’ve got a long way to go to fill in the gaps in our knowledge, or
even to find out what shapes those gaps are, but thousands of
researchers all around the world are working hard at it, and it’s
humanity that benefits along the way.
[1]
Depending on the definition you use, I may already be. Wikipedia
broadly defines a scientist as one who “[engages] in a systematic
activity to acquire knowledge”, or one that uses the scientific method,
of which I do both. Dictionaries however tend towards requiring some
knowledge of expertise, in which case proper experts might say I’m not a
scientist yet. Damn dictionaries. But hey, I’m trying.
[2] Vaccinated: One Man’s Quest to Defeat the World’s Deadliest Diseases, and Autism’s False Prophets.
[3]
Published in the prestigious, high impact journal BMJ, the articles are
freely available at http://www.bmj.com/content/342/bmj.c5258
[4]
In fact, just by acknowledging the existence of the anti-vaccine
movement has given them more credence then their ‘evidence’ deserves
(the acknowledgement makes up about 5.5% of the word count of this
article, which is far greater a weighting then their contribution is to
good science). There is no need to “teach the controversy”, as
scientifically speaking, there isn’t one. The data is out there, it’s
just up to people to read it.
[5] I was pretty tempted to end the article here, having already summed up most of my argument. You might be sorry I didn’t.
[6]
This is in contrast to the innate immune system, which protects us from
pathogens non-specifically, and doesn’t keep records of what it’s
already dealt with, hence immunity is provided by the adaptive system.
However, they are both just two sides of the same coin, and there’s a
lot of interplay between the two.
[7] These types relate to CD8+ cytotoxic killer T-cells, and CD4+
T-helper cells respectively. The latter cells (CD4+) are the cells that
are depleted during HIV infection, which causes the immunosuppression
that occurs in AIDS.
[8]
Further vaccinations are available for certain at risk groups, such as
for tuberculosis, hepatitis B, or chickenpox. Full details of the
recommended UK vaccination strategy can be found at
http://www.nhs.uk/Planners/vaccinations/Pages/Vaccinationchecklist.aspx
[9]
The World Health Organisation provides vaccination uptake estimations
by country here:
http://apps.who.int/immunization_monitoring/en/globalsummary/wucoveragecountrylist.cfm.
Estimates of herd immunity levels can be found at
http://www.bt.cdc.gov/agent/smallpox/training/overview/pdf/eradicationhistory.pdf.
[10]
You can check these out for your self at http://www.medicinenet.com,
but personally I recommend doing a google image search. Nothing drives a
point home like pictures of a festering brain abscess. Also worth
noting that I made up one of those causes of death, but I’ll let you
figure out which. Here’s a mini-glossary for some of those symptoms:
meningitis, an inflammation of the meninges, the membranes the surround
the spinal chord and brain tissues; bacteremia or septicaemia, bacteria
present in the blood; encephalitis, inflammation of the brain.
[11] See http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5518a4.htm and http://www.who.int/immunization_monitoring/diseases/en/
[12]
Both viruses and bacteria are implicated in human cancer formation,
such as Human Papilloma Virus, HPV, or Hepatitis B Virus which cause
cervical and liver cancer respectively, and Heliobacter pylori, which
causes stomach cancers.
[13] An antigen is the part of a molecule which is recognised or ‘seen’ by cells of the immune system.
[14] An autoimmune disease or disorder is when an individual’s
immune system mistakenly produces an immune response against other cells
of that individual, meaning that a person’s own immune system will
start attacking other cells in their body.
[15] Or they just take more and bigger hits until they start to feel
something, maybe. Who knows; it’s all still in development. But it’s
still damned interesting.
[16] Along with the time, money, resources and inclination. But the imagination is the important bit.
[17]
The most notorious of these in recent memory are probable the Cutter
Incident of 1955, where live polio virus contaminated stocks of polio
vaccine (through industrial carelessness and poor monitoring standards),
and the 1976 U.S. emergency swine flu vaccination program was
associated with a slightly increased risk of developing the neuropathic
Guillain-Barré syndrome.
[18] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1200696/?tool=pmcentrez
[19] Or 3 thousand million years, depending on which definition of ‘billion’ you use.
----
NB This was originally posted on my Newsgrape account. I think I originally started writing about something else, for a competition, but got completely sidetracked and wandered off with this.
