MICR2000 Module 4 L6: Vaccines

Who is regarded as the founder of modern vaccination?

Edward Jenner (1749–1823). He developed the smallpox vaccine in 1796, noticing that milkmaids exposed to cowpox were resistant to smallpox.

What is a vaccine?

A preparation derived from a pathogen that does not cause disease but induces protective immunity. Vaccines aim to prime the adaptive immune response so that a first infection triggers a faster, stronger secondary response.

What are the key features of an ideal vaccine?

Effective, safe, stable, and low-cost.

What human diseases have been eradicated or nearly eradicated with vaccines?

Smallpox (eradicated), Polio (types 2 and 3 eradicated, type 1 remains), and possibly measles in the future.

How does vaccination contribute to herd immunity?

By protecting individuals and reducing transmission in the population, thereby controlling spread even to those not directly vaccinated.

What are the main types of vaccines?

• Live attenuated (e.g., measles, mumps, Sabin polio, yellow fever) - weakened & ineffective

• Inactivated whole virus (e.g., Salk polio, rabies, Japanese encephalitis) - chemically treated and inactivated

• Inactivated subunit (e.g., influenza split vaccine) - inactivated by being split

• Recombinant subunit (e.g., Hepatitis B, HPV Gardasil) - come together

• Live recombinant/chimeric (e.g., dengue, JEV, WNV)

• DNA vaccines (experimental, e.g., WNV)

What are adjuvants and why are they used?

Substances that enhance the magnitude, breadth, and durability of the immune response to vaccines. Examples: Alum salts (since 1920), MF59 (oil-in-water emulsion for flu), CpG 1018 (in Heplisav-B), and GSK Adjuvant Systems.

What are mRNA vaccines and how do they work?

They deliver modified mRNA encoding a viral protein (like SARS-CoV-2 spike) into host cells via lipid nanoparticles. Cells translate the mRNA, producing antigen that stimulates immunity. Example: Pfizer and Moderna COVID-19 vaccines.

What are the advantages of needle-free vaccine patches (HD-MAP)?

Cutaneous delivery targets antigen-presenting cells, removes cold-chain needs, allows short application times, avoids needles, and enables potential self-administration.

Who developed the HPV vaccine and what impact did it have?

Prof. Ian Frazer (Australian of the Year, 2006). Gardasil, a subunit vaccine, showed 100% effectiveness against the most common HPV strains that cause ~70% of cervical cancers.