Pro-Vax Blog

The facts: Vaccines and the immune response
 

By Samantha White

 

Our bodies encounter thousand of germs (“pathogens”) everyday. Our immune system protects us from invading pathogens through mechanical barriers and non-specific cellular responses, and also through adaptive immunological responses. Vaccines aim to provide an individual with immunity against infectious agents that usually cause more severe and tolling diseases (and can sometimes even result in death!).

 

Infectious particles contain “antigens” which act as markers for our immune system to detect. When white blood cells see these markers, they tag the germ for removal by the immune response (production of “antibodies” specific for that germ). It takes time for the white cells to send out messenger molecules (cytokines) to attract more cells to an area of infection and begin producing antibodies. In this time, the invading pathogen has the opportunity to replicate and release toxins, causing disease symptoms. This then requires a greater immune response to eradicate the infection, and results in inflammation and fever, on top of symptoms of the disease itself, making the body sick and run down.

 

The immune response also produces what are called “memory cells”, which stay in the body long-term after the infection has been eradicated. These memory calls stay on the look out for that specific pathogen in case it enters the body again. This means that post infection or immunisation, your body will quickly recognise the germ and know exactly what antibodies to produce to combat the disease. So the body will fight off the few particles before they have a chance to replicate and cause disease symptoms! This is termed secondary response.

 

Vaccinations provide immunity by introducing a “fake disease” to the body. They evoke the same immunological response the wild infection would cause, without causing the disease.

This can be done through a variety of techniques, including:

Attenuated: the germ is weakened, limiting its ability to cause disease. Important point: these vaccines are not appropriate for immunocompromised individuals, as their immune systems might not be strong enough to fight even these weakened versions of a disease!

 

Inactivated (dead): the germ is killed, but still contains those important antigens, so the body will still recognise it and evoke an immune response.

 

Deactivated toxin: some bacteria produce harmful toxins, which cause disease. These can acts as targets for the antibodies too! These toxins will be deactivated so will not cause adverse effects on the body when in a vaccine.

 

Modified product: a good example of this is the HPV vaccine, where they only use the shell (capsule) of the virus particle, so the portion cannot cause disease, but the immune system still recognises the surface antigens of the virus.

 

Once the body has been exposed to the antigen, next time it enters the body
a strong secondary response will take over and eradicate the infection
before it causes symptoms.

 

Herd immunity occurs when a high enough proportion of a population is protected from an infectious disease. Vaccination gives immunity, and therefore  if above (usually) 90% of a population is immune; those who are not vaccinated (for a variety of reasons) are also protected from the disease. This is because those that are protected act as a barrier to transmission and interrupt the spread of disease. Measles is highly infectious and so requires a higher rate of protection - 95% to obtain herd immunity. This is why as vaccination rates fall in Australia, measles outbreaks are being seen more and more.

 

Recommended vaccines vary between countries. Australia’s vaccination schedule can be found at the link included at the bottom of the page. Some people within a population are at a higher risk due to their age or profession, and so are recommended to have additional vaccines.

 

Some examples are:
Travellers to high-risk area: Japanese encephalitis, Typhoid, Yellow fever

Military personnel: Neisseria meningitidis, Small pox, Anthrax

Health care workers: Hep B, Influenzae, MMR, Varicella, Pertussis

Elderly: Influenzae

Veterinarians: Anthrax, Rabies

 

We don’t see vaccine preventable diseases in our community very often these days. This is thanks to vaccination programs and improved hygiene and sanitation. Some people of the younger generations don't realise how devastating these diseases can be. For example poliomyelitis, a crippling and sometimes lethal disease, was eradicated in Australia through vaccination years ago, so many young Australian's haven't seen the overwhelming difference to healthcare that vaccines have made. If vaccination rates fall, we will see a rise in incidence of these vaccine preventable diseases. People need to understand that the side effects and risks of immunisation doesn’t come close to the effects of these horrible infectious diseases (see tab "side effects").

 

Current Australian vaccination schedule for children

http://www.immunise.health.gov.au/internet/immunise/publishing.nsf/Content/nips-ctn

 

 

Fun facts!

 

Passive vaccinations are where an antibody is injected (rather than an antigen), usually post-exposure. This gives a person short-term protection from infection, and is commonly used for rabies virus, and also as anti-venom for snakebites!

 

Edward Jenner was the first scientist to describe vaccination over 200 years ago. He found that injecting humans with the fluid from cowpox lesions protected them from the smallpox virus. We now know this is because cowpox (vaccina virus) and smallpox virus have an antigen (epitope) in common, so antibodies against one can combat the other!

 

Vaccinations are usually given to children, as they are more vulnerable to infection than adults due to an immature immune system.

 

 

Interesting Videos
 

Documentary: Jabbed - love, fear and vaccines (by Genepool productions)

 

YouTube videos:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sources

 

Coico R, Sunshine G. Immunology: a short course. 6th ed. Hoboken, New Jersey: Wiley-Blackwell; 2009.

 

Ademokun A, Dunn-Walters D. Immune responses: primary and secondary. eLS John Wiley & Sons Ltd. 2010.

 

Jabbed: love, fear and vaccines. Genepool prodcutions, 2013.