# Everyone is a writer

How does the vaccine work? How to develop vaccines?

1.       WEAKEN THE VIRUS - Using this strategy, viruses are weakened so they reproduce very poorly once inside the body

Examples: The vaccines for measles, mumps, German measles (rubella), rotavirus, oral polio, chickenpox (varicella), and influenza (intranasal version) vaccines

Advantage:  One or two doses provide immunity that is usually life-long

Limitation:  These vaccines usually cannot be given to people with weakened immune systems (like people with cancer or AIDS)

2.       INACTIVATE THE VIRUS - Using this strategy, viruses are completely inactivated (or killed) with a chemical. By killing the virus, it cannot possibly reproduce itself or cause disease

Examples: The inactivated polio, hepatitis A, influenza (shot), and rabies vaccines

Benefits - The vaccine cannot cause even a mild form of the disease that it prevents and can be given to people with weakened immune systems. Limitation- It typically requires several doses to achieve immunity

3.       USE PART OF THE VIRUS - Using this strategy, just one part of the virus is removed and used as a vaccine

Examples: The hepatitis B, one shingles vaccine (Shingrix®) and the human papillomavirus (HPV) vaccines. The vaccine is composed of a protein that resides on the surface of the virus

Benefits - These vaccines can be given to people with weakened immunity and appear to induce long-lived immunity after two doses

4.       USE PART OF THE BACTERIA - Some bacteria cause disease by making a harmful protein called a toxin. Several vaccines are made by taking toxins and inactivating them with a chemical

Examples: The diphtheria, tetanus and pertussis vaccines

Another strategy to make a bacterial vaccine is to use part of the sugar coating (or polysaccharide) of the bacteria. Protection against infection by certain bacteria is based on immunity to this sugar coating (and not the whole bacteria)

Examples: The Haemophilus influenzae type B (or Hib), pneumococcal, and some meningococcal vaccines

Is there any bottlenecks to develop vaccines?

-       The main research bottlenecks in vaccine development is related to understanding pathogen biology, identification of appropriate animal models and investment in the manufacturing sciences, especially into process development

-          Major bottlenecks are - Process Development to create a scalable, GMP compliant, manufacturing process and the determination of the critical process parameters

-          Few are encountered with animal testing in the laboratory and related processes