Vaccination and Drug Development

Vaccination

Definition of Vaccination: An injection of a dead or inactive pathogen that stimulates the immune system to produce antibodies without causing disease because the pathogen is rendered harmless.

Pathogen Entry:
- A pathogen enters the body.
- It secretes toxins or destroys cells which make the person feel ill.
Role of White Blood Cells:
- White blood cells create antibodies to destroy pathogens.
Immune System Memory:
- If the same pathogen tries to infect the person again, the immune system remembers how to produce the correct antibodies to kill the pathogen quicker.
- The person is now immune to that pathogen.
The Issue:
- To become immune, a person must catch the disease and suffer the effects initially. This is where vaccines come into play.

Mechanism of Vaccines:
- Vaccines consist of dead or inactive pathogens that cannot cause illness but are recognised by the immune system.
- These dead antigens trigger the production of antibodies, preparing the immune system for future encounters with the live pathogen.
Response to Future Infections:
- If live pathogens of the same type appear after vaccination, white blood cells can rapidly produce antibodies to kill the pathogen.

Pros:
- Disease Prevention: Vaccination helps prevent diseases.
- Control of Diseases: Vaccines have significantly helped control diseases such as Polio and Measles.
- Prevention of Outbreaks: Help prevent outbreaks by ensuring widespread immunity.
Cons:
- Vaccines do not always work for every individual.
- Possible adverse reactions can occur (e.g., fevers, seizures).

Definition of Herd Immunity:
- Vaccinating the majority of a population to prevent the spread of disease, as there will not be enough hosts to carry the disease to vulnerable individuals.

Painkillers:
- Function: Painkillers relieve symptoms but do not tackle the cause of the disease or kill pathogens. The pathogens remain present.
- Common Examples: Include Asprin, Paracetamol, cough medicine which alleviate symptoms like coughing, headache, and body pain.
Antibiotics:
- Definition: Antibiotics are medications that treat diseases by killing or preventing the growth of bacteria without harming human body cells.
- Specificity: Different antibiotics target specific types of bacteria, emphasising the need for the correct antibiotic to treat the infection.
- Viral Infections: Antibiotics do not destroy viruses as they reproduce within the body’s cells, making it complex to eliminate viruses without also harming human cells.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Mechanism of Resistance:
- Bacteria can mutate and develop resistance to antibiotics. In cases of infections, some bacteria may be resistant.
- This results in only non-resistant bacteria being killed during treatment, allowing the resistant bacteria to survive and reproduce.
- Over time, this can lead to a population of bacteria that is resistant to available antibiotics, making infections harder to treat.
Mitigation Strategies:
- It is important to avoid over-prescribing antibiotics.
- Patients should always finish the entire course of antibiotics to reduce the risk of developing resistant strains.

Historical Context:
- Many drugs were originally derived from plants, which produce various chemicals as defense mechanisms against pests or pathogens.
- These plant chemicals have been studied and utilized in the development of drugs to treat human diseases or relieve symptoms.
Examples of Plant-Derived Drugs:
- Aspirin: A painkiller developed from chemicals found in the willow tree.
- Digitalis: Used for heart conditions, derived from foxgloves.
- St. John’s Wort: Used as a blood thinner.
Microorganism-Derived Drugs:
- Discoveries, such as Penicillin, were made by studying microorganisms.
- Case Study: Alexander Fleming discovered Penicillin when observing that a mold (Penicillium notatum) killed bacteria on a petri dish. A control experiment showed bacteria grew in a dish without the mold but not in the presence of mold.

Drug Testing Process:
- New drugs undergo a thorough testing procedure before being released to the public.
- Initial Testing: Conducted on cells and tissues in lab settings due to ethical concerns about using human tissues.
- This stage provides a preliminary assessment but is not comprehensive.
- Animal Testing: Drugs must be tested on live animals (e.g., mice or rabbits) to assess efficacy and toxicity since they share mammalian biology with humans.
- Ethical implications arise regarding animal testing practices.
- Some argue that differences between humans and animals can lead to ineffective treatments.
- Testing on Healthy Volunteers: When moving to human testing, drugs are given to healthy individuals to identify toxicity and side effects starting with a very low dose and gradually increasing it.
- Clinical Trials: Conducted with patients suffering from the condition the drug is meant to treat to determine efficacy and optimum dosage with minimal side effects.

Structure of Clinical Trials:
- Patient groups are divided into those receiving the new drug and those given a placebo (an identical pill without active medication).
- Purpose of Placebo: Comparison allows for distinguishing the actual effects of the drug from psychological effects (placebo effect) where patients feel better just because they expect to due to taking medication.
Trial Integrity:
- Blind Trials: In many studies, patients do not know whether they are taking the drug or placebo, and sometimes doctors are also blinded until results are in to prevent bias.
- Peer Review: Results must undergo peer review before publication to ensure validity and prevent false claims.
Key Terms:
- Efficacy: How well the drug works and produces the desired effect.
- Toxicity: The level of harm the drug can cause.
- Dosage: Refers to the concentration administered and how frequently the drug is taken.