Vaccines Against Disease

• Vaccination:

  • Vaccines are used to induce immunity to infectious diseases
  • A vaccine contains harmless versions of a pathogen
  • There are several different methods by which scientists ensure that vaccines contain harmless pathogens such as:
  • Killing the pathogen
  • Making the pathogen unable to grow or divide (attenuated vaccine)
  • Using fragments of pathogens, which include the necessary antigens (rather than whole cells)
  • A vaccine may be administered orally, nasally or via an injection
• How vaccines work:

  • Once in the bloodstream, the antigens contained within the vaccine can trigger an immune response in the following way:
  • Lymphocytes recognise the antigens in the bloodstream
  • The activated lymphocytes produce antibodies specific to the antigen encountered
  • Memory cells and antibodies subsequently remain circulating in the bloodstream
• The process of long-term immunity by vaccination:

  
• The process of long-term immunity by vaccination:

  
• The process of long-term immunity by vaccination:

  
• • Future infection by the same pathogen will trigger a response that is much faster and much larger compared to the initial response
  • Due to the rapid nature of the response, the pathogen is unable to grow in sufficient numbers to cause disease and the individual is said to be immune
• The number of measles antibodies in the blood following vaccination. The secondary response is much faster and a greater number of antibodies are produced:

  
• Other non-vaccine medicines: antibiotics, antivirals and antiseptics:

  • Antibiotics are chemical substances produced by one microorganism that has a toxic effect on another, pathogenic organism
  • Antibiotics have been an important branch of medicine for decades since their discovery in the 1930s
  • They generally only work against bacterial pathogens (not fungi or viruses)
  • Penicillin is the first and best-known example
• Other non-vaccine medicines: antibiotics, antivirals and antiseptics:

  • Antivirals are medicines that act against viruses only
  • It is difficult to target viruses without damaging host cells 
  • A risk is that because viruses use host cell mechanisms to replicate themselves, damaging the virus may well inflict collateral damage on the host cell
  • Most antiviral drugs act by slowing the virus's rate of reproduction down
  • Can a virus be killed as it's debateable whether a virus is a living entity in the first place!
  • A well-known example is the anti-flu drug TMTamiflu
• Other non-vaccine medicines: antibiotics, antivirals and antiseptics:

  • Antiseptics are products that kill microorganisms but are not drugs because they would be toxic if taken
  • They can be used externally eg. on the surface of the skin to clean wounds 
  • Examples include TMLysol, a common laboratory antiseptic used to wipe surfaces before and after microbiological work, and common household antiseptics like bathroom cleaners
• Advantages & Disadvantages of Vaccination:

  Why vaccinate?

  • Vaccination will prevent illness in an individual by providing artificial immunity
  • Vaccination involves exposing an individual to the antigens of a pathogen in some form, triggering an immune response which results in the formation of memory cells which can make antibodies against it
  • If a vaccinated individual is infected with the pathogen, they can destroy the pathogen before it becomes infectious
• Advantages & Disadvantages of Vaccination:

  • Consequently, vaccines reduce the likelihood that an infected individual will spread the pathogen they have been vaccinated against to others
  • If a large proportion of the population is vaccinated, it is unlikely that an unvaccinated individual will become infected with the pathogen
  • This is the principle behind the idea of herd immunity
• Advantages & Disadvantages of Vaccination:

  • There are three main scenarios with vaccination:
  • There are no vaccinations and the disease spreads quickly
  • Some of the population are vaccinated and the disease spreads to fewer people
  • Most of the population are vaccinated and this prevents the spread
• Herd immunity protects the vulnerable that may not be able to have the vaccine:

  
• Herd immunity protects the vulnerable that may not be able to have the vaccine:

  
• Worldwide vaccination:

  • The role of the World Health Organisation (WHO) is to monitor global diseases, they will track if a disease is an epidemic (localised outbreak) or a pandemic (global outbreak)
  • For example, The WHO declared the COVID-19 outbreak a pandemic on 11 March 2020
• • The importance of vaccines cannot be underestimated:
  • The number of people with measles worldwide is increasing even though there is a vaccine
  • The increase is due to a drop in the vaccination rate globally
  • There was some controversy over the MMR vaccine in 1998 and the number of vaccinations dropped significantly after this
  • Vaccines have reduced the cases of diseases worldwide drastically
• Vaccination Statistics Table:

  
• Advantages & Disadvantages of Vaccination Table: