(8) How can our health be further protected from pathogens?

Fighting infections with vaccinations - immunisation! and the 'pros' and 'cons' of vaccination

Be able to explain how the treatment of disease has changed as a result of increased understanding of the action of antibiotics and immunity.

Immunisation is the action of making a person or animal immune to infection, typically by inoculation with a vaccine.

• Immunity is a defence against a pathogen by antibody production in the body.

• Immunity can be gained by pathogen infection or from vaccination.

• These procedure aid the function of our immune system.

Be able to evaluate the consequences of mutations of bacteria and viruses in relation to epidemics and pandemics - data provided.

Be able to evaluate the advantages and disadvantages of being vaccinated against a particular disease - data provided.

As already mentioned, Semmelweiss recognised the importance of hand-washing in the prevention of spreading some infectious diseases.

By insisting that doctors washed their hands before examining patients, he greatly reduced the number of deaths from infectious diseases in his hospital.

Some medicines, including painkillers, help to relieve the symptoms of infectious disease, but do not kill the pathogens.

As we have seen, our immune system of the body produces specific antibodies to kill a particular pathogen.

This leads to immunity from that pathogen.

In some cases, dead or inactivated pathogens stimulate antibody production.

If a large proportion of the population is made immune to a pathogen by vaccination-immunisation, the spread of the pathogen is very much reduced - which is what the next section is all about

Vaccination-Immunisation

If you become infected with a new ('foreign') pathogen that your immune system doesn't recognise as 'friendly', it takes your white blood cells a few days to produce the antibodies to protect you.

In the mean time you are unfortunately ill and not feeling well to a greater (fatal) or lesser (a bit poorly) degree.

Vaccination is a successful method to drastically reduce the response time of your immune system and usually prevents the onset of the disease.

People can be immunised against a disease by introducing small quantities of dead or inactive forms of the pathogen into the body (vaccination).

The process of vaccination has radically changed the way we fight disease because it is not about treatment of a disease, it is all about preventing the effects of an infection.

Know that vaccination is an important method of preventing infection.

What is vaccination? What is a vaccine? What is immunisation?

Vaccination protects the individual from future infections and mass scale vaccination can greatly reduce the incidence of disease.

Protection is better than cure! If you become infected with a pathogen, it takes a few days for your white cell immune system to deal with the microorganism, and you can become quite ill in a few days.

Vaccination is the process of injecting the individual with small amounts of specific harmless dead/inactive microorganisms (pathogens) which carry the antigens that cause the immune system to produce the corresponding protective antibodies - even though the pathogen is in a harmless form.

Different vaccines are required for specific pathogens e.g. flue, HPV (human papilloma virus), polio and whooping cough all have their own vaccine.

The MMR vaccine contains weakened versions of the viruses that cause measles, mumps and rubella (German measles) and is very effective in aiding our immune system to fight these pathogen infections.

As well as injection, MMR vaccines can be taken orally or using a nasal spray.

So, vaccines automatically stimulate the white blood cells to produce antibodies that destroy the invading 'foreign' pathogens - essentially aiding our immune system.

This makes the person immune to future infections by the microorganism ie gives the individual immunity from further attacks - the overall process is referred to as immunisation.

If the same type of pathogen, that you have been vaccinated against, enters your body, your body can respond by rapidly making the correct antibody, in the same way as if the person had previously had the disease.

Vaccination is when the vaccine is administered to you (usually by syringe injection).

Immunisation is what happens in your body after you have the vaccination.

The vaccine stimulates your immune system so that it can recognise the disease (invasive pathogen - bacteria or virus) and protect you from future infection (i.e. you become immune to the infection).

The diagram and notes below what happens on vaccination to complete the immunisation effect.

1. You are injected by vaccination with a weakened/inactive/dead form of the pathogen - although harmless, your body will respond to the 'new' antigens detected - an immune response.

2. Your lymphocyte white blood cells recognise the pathogen as harmful and produce the antibodies to counteract 'what is perceived' as an active pathogen.

3. If the same actually active pathogen enters your body, it is quickly recognised by its antigen molecules and attacked by the specific antibodies already present and more can be made too, quite rapidly.

4. The effect of the pathogen is 'neutralised' so you don't become ill.

5. When the pathogens are combined with the antibodies they are much more susceptible to be ingested by the phagocyte white blood cells and destroyed.

MMR vaccine is used to triple protect children against measles, mumps and rubella (German measles).

The vaccine contains weak inactive versions of three viruses that cause measles, mumps and rubella.

The effects of vaccination can 'wear off' over time, and booster injections maybe necessary to increase the levels of the protective antibodies.

The graph above illustrates the possible sequence of events involving immunisation

The body is first vaccinated with a dead or inactive form of the pathogen.

In the body's primary response, the lymphocytes recognise the antigens and produce the specific antibodies to counteract the perceived threat of the form of the pathogen in the vaccine.

Eventually, the body stops responding to the vaccination, and the antibody concentration falls, but NOT to zero!

The memory lymphocytes retain the information to recognise the shape of the antigen if an infection of the same pathogen occurs. The body has been immunised to fight this particular pathogen.

If the body becomes re-infected with the same pathogen, the memory lymphocytes immediately recognise the pathogen antigen and rapidly make lots of the specific antibodies.

So, the 2nd response of your immune system is faster and stronger compared to the original vaccination. The immunisation has worked.

The specific antibody reaches a maximum concentration to fight the antigen.

As the infection is gradually overcome the antibody concentration falls.

 

There are arguments for and against vaccination (the 'pros and cons')

For vaccination - immunisation:

Vaccines have resulted in the large scale control of many infectious diseases that were once common and often fatal e.g. measles, mumps, polio, rubella, smallpox, tetanus, whooping cough etc.

These communicable diseases were once common in the UK but smallpox has been completely eradicated and polio infections are very rare these days (down as much as 99%)

Epidemics are less likely with mass vaccination - spread of the disease is less likely as there are fewer infected people to carry an active form of the disease - but a large percentage of the population needs to have been vaccinated - less people around to carry and pass on the pathogen.

This means people who aren't immunised, are less likely to catch the disease as there are far less people to pass it on. This situation is known as 'herd immunity'  - lots of people have the antibodies to combat the pathogen and therefore far less people can be carriers of the pathogen..

Herd immunity is defined as the resistance to the spread of a contagious disease within a population that results if a sufficiently high proportion of individuals are immune to the disease, especially through vaccination - in either case, lots of people have the antibodies to combat the pathogen and therefore far less people can be carriers of the pathogen..

Without mass vaccination an outbreak of epidemic proportions is much more likely - many more people potentially to carry and transmit the disease which can spread rapidly, particularly in densely populated areas where lots of people are in close contact.

A notes of caution on using vaccines!

(i) After the two 'shots' of the MMR vaccine as a child, your protection from measles, mumps and rubella should last you a lifetime.

(ii) Others, like the injection for protection against the tetanus bacterium and polio virus, only give you immunity for about 10 years - so, in many cases of vaccination, you need booster doses.

(iii) Due to mutations of the flue virus strains, your immunity lasts a year and you need a fresh 'flue jab' before every winter - but this is your choice, highly recommended for older people like me!

(iv) No vaccine has been developed to protect us from the common cold or the HIV virus.

Against vaccination - immunisation:

Immunisation programmes are not always successful - some vaccines do not always give you immunity.

So, development work goes on all the time to make more effective vaccines - especially as different strains of viruses and bacteria are constantly evolving.

There may also be side-effects in which the 'patient' has a bad reaction to a particular vaccine eg swelling, fever, seizure (serious!), but such reactions and complications are rare and the mass good effect of large scale immunisation should be balanced against the very rare negative effect - however serious this might be.

There are some concerns over using 'whole' pathogens so that the vaccine actually causes disease in the person. Therefore some vaccines only use parts of the pathogen cells which must include the antigens for the white blood cells to react to.

Producing vaccines and carrying out mass vaccination programmes can be expensive - the disease may be rare or the vaccine proves to be not that effective.

The benefits of vaccination must outweigh the development and production costs involved.

There is a very small risk involved with most medical treatments

Side-effects, usually minor, are not uncommon, BUT, without vaccination some of these diseases are fatal or have very serious non-fatal outcomes - people can die of from measles, rubella has serious consequences for pregnant women, there can be serious complications for infected people who have not been vaccinated.

Following a seaside accident - cut on knee, as an eleven year old, I collapsed unconscious after a tetanus injection at a local hospital. I was ok within half an hour BUT my parents got a bit of a shock!

Parents of young children are always given details of vaccination schedules and where appropriate, warned of side effects associated with specific vaccines.

Sadly in some countries, including in the UK, a lot misinformation has been put about on social media about the supposed ill-effects of taking the MMR (mumps, measles and rubella) vaccine e.g. causing autism. The information was not backed up by real scientific data and as a result was hundreds of thousands of young children were not vaccinated with three medical conditions with potentially serious consequences.

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Passive immunity

Know and explain that passive immunity is only a short-term defence of antibodies against pathogens.

Passive immunity can be acquired from another individual, e.g. from mother to infant in breast feeding.

However, know that

(i) memory cells are not produced in passive immunity,

(ii) BUT,  the gaining of passive immunity is really important for breast-fed infants.

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Learning objectives for this section on immunisation

Be able to describe and explain fighting infections using vaccination and immunisation e.g. the MMR 'jab'.

Be able to discuss the advantages disadvantages of immunisation, and that the immunity produced is aiding our immune system.

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