NCEA Level 3 Biology: Comprehensive Guide to Socio-Scientific Issues Surrounding Vaccination

Overview of the Human Immune System

• The human immune system is a complex and intricate network of organisms, including chemicals, white blood cells ($\text{WBCs}$), proteins, and organs.

• Its primary function is to exterminate unwanted pathogens and bacteria, heal injuries, and adapt to overcome new germs and viruses.

• The system is divided into two primary sub-systems: the Innate Immune System and the Adaptive Immune System.

• Reference ID: lOMoARcPSD|64534701.

The Innate Immune System

• The innate immune system serves as the body's initial line of defense. It utilizes physical and chemical barriers, specialized killing cells, and temperature regulation to maintain health.

• It is categorized into external and internal defenses.

External Defenses

• Mucous Membranes: These provide the first point of contact for airborne pathogens. Mucus, a slimy gel found in the throat, lungs, mouth, stomach, and intestines, traps and destroys harmful pathogens before they can enter the body.

• Skin: This organ consists of proteins, fats, minerals, and water. It serves as a physical barrier against bacteria and germs and regulates body temperature. This regulation is vital because excessive heat can denature enzymes. For example, if temperature rises too high, hydrolytic enzymes in neutrophil granules would denature and fail to fuse with pathogen-containing phagosomes to destroy microorganisms.

Internal Defenses: Phagocytes

• If the skin barrier is breached, phagocytes are the first cells to arrive at the site to ingest and kill foreign pathogens. There are two primary types:

  • Macrophages: These $WBCs$ are produced in bone marrow and settle in tissue. They swallow pathogens whole and can consume roughly $100$ pathogens before becoming full. They are divided into:

    • Fixed Macrophages: Attached to organ fibers, using cytoplasmic extensions to pull in suspicious matter.

    • Free Macrophages: Assertively roam tissue to engulf intruders.

  • Neutrophils: Also produced in bone marrow, these cells move to injured sites to kill pathogens via phagocytosis. Bone marrow produces approximately $100\text{ billion}$ neutrophils per day ($10^{11}$). They have a short lifespan of $1-2$ days and "assassinate themselves" after engulfing a pathogen to protect the body.

  • Leukocytosis: When neutrophils and other cells die, they release chemicals that attract more $WBCs$ to the site. Dead cells eventually form white or yellow pus. If the immune system is losing the battle, macrophages release pyrogens, chemicals that induce fever by raising the body's temperature to burn out pathogens.

Internal Defenses: Natural Killer (NK) Cells

• Natural Killer (NK) Cells are lymphocytes produced in bone marrow with a lifespan of approximately $2\text{ weeks}$.

• They roam lymph and blood to identify infected or diseased cells (e.g., malignant cells).

• Identification Mechanism: They identify healthy cells by the presence of the protein MHC1 (Major Histocompatibility Complex). Infected cells stop producing this protein.

• Elimination Process: NK cells release granzymes and perforin (toxic proteins) to trigger apoptosis, which is certain cell death.

The Inflammatory Response

• Mast Cells: These cells react to injury by sending out histamine molecules, causing heat and redness.

• Redness: Caused by leukocytes and enzymes like elastase and protease working on tissue repair.

• Heat: Increases the metabolic rate of cells, accelerating the healing process.

• Swelling: Chemicals like histamine, bradykinin, and prostaglandins cause blood vessels to leak fluid. This localized swelling increases blood flow, bringing more $WBCs$, enzymes, and minerals to the site.

The Adaptive Immune System

• This system targets specific pathogens that have bypassed the innate system.

B-Cells

• B-cells are lymphocytes responsible for producing specific antibodies for specific antigens.

• They are immunocompetent (able to recognize and bind to antigens) and self-tolerant.

• Each B-cell is covered with approximately $10,000$ membrane-bound antibodies acting as receptors.

• Upon binding with a compatible antigen, the B-cell is activated and clones itself. Some of these become long-lived memory cells, which store the genetic material for the specific antibody.

T-Cells

• T-cells are categorized into several types, including Helper, Cytotoxic, Memory, Suppressor, and Natural Killer (different from innate NK cells).

• Activation requires an Antigen-Presenting Cell (APC), which attaches pathogen evidence to an MHC structure.

• MHC Types:

  • MHC-I: Binds with CD8 receptors on Cytotoxic T-cells. Activated cytotoxic T-cells release granzymes and perforins to cause apoptosis in infected cells.

  • MHC-II: Binds with CD4 receptors on Helper T-cells. Activated helper T-cells send signals to other cells and replicate to create more helpers and memory cells.

Mechanism of Antibodies and Vaccination

• Antibodies: Proteins on cell surfaces that bind to antigens to remove them. Mechanisms include:

  • Neutralization: Physically blocking antigen binding sites so they cannot attach to tissue.

  • Agglutination: Antibodies bind to multiple antigens simultaneously, causing them to clump together. This makes it easier for macrophages to consume them.

• Vaccines: Substances designed to boost the immune system against specific pathogens using weak or dead pathogens to "impersonate" the antigen. This triggers B-cells and T-cells to create antibodies and memory cells for future encounters.

Types of Vaccines

• Live Attenuated Vaccines: Contain weakened but alive pathogens. They trigger a strong immune response, often providing lifelong immunity with $1-2$ doses. However, they cannot be given in large doses and are unsafe for the elderly, very young, pregnant, or immunocompromised individuals.

• Inactive Vaccines: Formed from dead pathogens. Because they cannot replicate, they are safe for immunocompromised and pregnant individuals. They are less intense and usually require multiple doses (e.g., the Influenza vaccine).

• mRNA Vaccines: Function by using mRNA copies of harmless spike ($S$) proteins from a pathogen (e.g., Pfizer vaccine for Covid-19). Cells produce the harmless spike protein, allowing the immune system to recognize it. Once the protein is formed, the cell destroys the mRNA. There is no risk of contracting the virus from the vaccine.

Biological Implications in Aotearoa New Zealand

• Individual Health and Survival: Comparison of the MMR (Measles, Mumps, Rubella) vaccine versus the diseases.

  • Measles: Causes rash, flu-like symptoms, brain swelling, chest infections, or death.

  • Mumps: Causes salivary gland swelling, hearing loss, meningitis, or encephalitis.

  • Rubella: Causes mild rash in adults but severe birth defects (deafness, heart/brain damage) or death in unborn babies.

  • MMR Statistics: Between $2000$ and $2023$, MMR vaccines saved globally up to $60\text{ million}$ lives. Over the last $50\text{ years}$, vaccinations overall have saved $154\text{ million}$ lives.

• Herd Immunity: A process where approximately $95.0\%$ of a population is vaccinated, protecting those who cannot be (due to age, pregnancy, or health conditions) by slowing the spread and reducing mutation chances.

  • Smallpox Case Study: Organized by the WHO in $1967$, a worldwide immunization plan led to smallpox eradication. The last natural case was in Somalia in $1977$, and it was declared eradicated in $1980$.

Social and Economic Implications

• Economic Impact: On March $26, 2020$, Aotearoa entered a two-month national lockdown. This led to decreased revenue for small businesses and a drop in national GDP between March $2020$ and March $2021$.

• Vaccine Costs: While many are free, the Shingrix (shingles) vaccine can cost between $\$600$ and $\$800$ for two doses (with $70.1\%$ effectiveness).

• Labor Market: Vaccination stations provided increased hours and income for health professionals.

• Reopening: The introduction of the Pfizer vaccine in February $2021$ allowed for the lifting of mandates and lockdowns, leading to an increase in GDP as consumer confidence returned.

Ethical Implications: Equity vs. Equality

• The Equity Argument: Statistics show certain groups are more vulnerable. A $15\text{-year}$ study ($1994-2008$) by Otago University found:

  • Māori (ages $65-79$) are $3.6$ times more likely to die of influenza than those of European/other ethnicity.

  • Pacific People (ages $65-79$) are $2.4$ times more likely to die of influenza.

  • Males are $1.9$ times more likely to die than females in the same age group.

• The Controversy: Prioritizing these groups protects the most vulnerable but leaves others (pregnant women, autoimmune individuals) at risk. Conversely, prioritizing the young ensures the nation's future and labor force but risks high mortality and hospital costs for the elderly, which increases taxation for free healthcare.

• Religious Exceptions: The Fluenz nasal vaccine contains porcine Type A gelatin, making it inaccessible for Muslim and Jewish communities. Herd immunity is essential to protect these unvaccinated groups.

Questions & Discussion

• Viewpoint: For Vaccinations: Dr. Helen Petousis-Harris, an associate professor at Auckland University with a PhD in vaccinology. She serves as the chair of the Global Advisory Committee of Vaccine Safety (GACVS) for the WHO and Co-director of the Global Vaccine Data Network (GVDN). She asserts that vaccines facilitate the world "getting back to what we know as normal."

• Viewpoint: Against Vaccinations: Sue Grey, an environmental lawyer and co-leader of the NZ Outdoors and Freedom Party. Despite a background in microbiology and biochemistry from Otago University, she distrusts pharmaceutical companies and the government, claiming the Covid-19 vaccine was developed too quickly. She utilizes social media (facebook) to share petitions against "mRNA jabs" and mandates.

• Personal Position and Advocacy: The author supports vaccinations based on scientific evidence. Proposed actions include using social media (like the WHO Instagram account with $12\text{ million}$ followers) to spread awareness.

• Confronting Misinformation: Dr. Peter Hotez is cited for using X (Twitter) to challenge unscientific claims by figures like Robert Kennedy Jr., though this often leads to personal harassment by "anti-vaxxers."

Validity of Sources

• Sources are considered reliable as they originate from government bodies (Te Whatu Ora, Ministry of Health, National Library of Medicine) or educational institutions (Auckland University, Otago University).

• Most data is current, having been published or updated within the last $5\text{ years}$.

• Wikipedia was used for information on Sue Grey but noted for potential unreliability due to its open-edit nature.