The revolutionary weapon for immunisation was inspired by the Latin word "vacca," which means "cow." Yeah! You heard it right! .The name ‘vaccine’ was derived from the cowpox virus.
The world was introduced to vaccines when Edward Jenner discovered the smallpox vaccine in 1796. He inoculated eight-year-old James Phipps with material from a cowpox sore on the hand of a milkmaid. Phipps suffered a local reaction and felt sick for several days, but made a full recovery. In 1980, we were able to eradicate smallpox, which was a significant medical breakthrough. Since the COVID-19 outbreak, the general public has become more aware about vaccines. Vaccines are simple to understand, so this is a brief overview of vaccines.
What are vaccines?
Vaccines are biological concoctions that are intended to produce acquired immunity to infectious diseases.These preparations contain either killed or weakened forms of the pathogen, its toxins, or any component of the pathogen. When the vaccine is injected, it stimulates the body's immune system to produce antibodies in the same way that it would if the body were exposed to the disease. Vaccines are similar to preventive measures (aka prophylaxis). However, not all vaccines are used for prophylaxis; some are also used for therapeutic purposes.
How are these vaccines developed?
Vaccine development is a time-consuming, intricate process that typically takes 10–15 years. This is due to the fact that vaccine development, testing, and regulation must adhere to a set of standardised procedures and guidelines.
Research and discovery
Scientists conduct laboratory research to discover the best vaccine for a specific infectious disease. The research moves on to the next stage after establishing a rationale for a vaccine and its viability.
Pre-clinical development
A vaccine's safety, immunogenicity, and mechanism are studied in cell or tissue culture systems as well as in animals. Several animal challenge studies were carried out in order to determine safe dosing.
Clinical development is the stage at which vaccines are tested on humans.
Clinical trials are carried out in accordance with the highest scientific and ethical standards. Scientists, researchers, and medical professionals carefully analyse the trial results. Regulatory authorities also inspect vaccine manufacturing facilities to ensure that they are in accordance with current Good Manufacturing Practice regulations.
Approval and Licensure
The benefits of the vaccine must outweigh the risks, and the vaccine must also be safe and effective before an official body (like the US FDA) grants it a licence allowing it to be used by the general public.
Phase 4: Vaccine post-licensure monitoring
The primary goal of the Phase 4 trial is to track adverse drug reactions after the vaccine has been approved for public use. As part of its work to make vaccine recommendations, a group of medical and public health experts carefully reviews vaccine safety and effectiveness data.
Vaccine manufacturing begins after a vaccine has been licenced. Vaccines are manufactured in batches, and vaccine manufacturers must test all lots of a vaccine to ensure that they are safe, pure, and potent.
Summarizing the stages of vaccine development and testing
COVID 19 vaccine development was super fast: How was it possible?
The mumps vaccine took about four years to go from development to distribution (1960). However, COVID-19 vaccines have shattered the previous record.
Thanks to novel technologies that made it possible!
Approaches of vaccine designing
Whole-microbe appraoch
Live attenuated vaccine
As the name implies, a living but weakened version of the virus is used to create this type of vaccine. With only one dose, this type of vaccine typically produces strong cellular and humoral immune responses.Live vaccines are not generally safe for immunocompromised patients. The Measles, Mumps, Rubella (MMR) vaccine and the chickenpox vaccine are examples of this type of vaccine.
Inactivated vaccine
They are also known as "killed" vaccines. Heat, chemicals, and radiation are used to inactivate the virus and reduce its virulence. These vaccines are safe, easy to store, and transport. This type of vaccine does not elicit cellular responses and requires multiple booster doses. Rabies, polio, and Hepatitis A vaccines are examples of this type of vaccine.
Viral-vector vaccine
This type of vaccine employs a safe virus to deliver specific sub-parts known as "spike proteins" of the virus of interest in order to elicit an immune response without causing disease. The safe virus then acts as a platform or vector to deliver the spike protein into the body. The immune response is triggered as a result of the spike. This type of vaccine is generally considered to have a good safety profile and can induce strong humoral and cellular responses with a single dose. The Ebola vaccine is one example of this type of vaccine (rVSV-ZEBOV).
The Subunit Approach
A subunit vaccine is one that only uses the subunits (antigens) of a virus or bacterium. The immune system recognises these subunits and stimulates the production of antibodies .The subunits can be proteins or polysaccharides. It can be safely administered to immunosuppressed people. Most of the vaccines on the paediatric immunisation schedule are subunit vaccines, such as whooping cough, tetanus, diphtheria, and meningococcal meningitis.
Virus-like particles vaccines
Virus-like particle vaccines explore the immunogenicity of empty virus particles by presenting several copies of the same antigen on their surface. They contain repetitive high-density displays of viral surface proteins. They are designed to mimic the virus structure, thereby triggering strong immune responses against the antigens presented on their surface; they have good safety profiles because they lack the pathogen’s genetic material. The human papillomavirus vaccine and the hepatitis B vaccine are examples of this type of vaccine.
The Genetic approach
It is also known as a nucleic acid vaccine. A part of genetic material is used. It can be DNA or mRNA, which undergoes translation to construct proteins. The immune system recognises these proteins and stimulates the production of antibodies. These types of vaccines can induce humoral and cellular responses. DNA vaccines require a special delivery platform.
A quantum leap in genomic sequencing, new technologies used in vaccine making, expedited research, and clinical trials aided in the fast-paced development of COVID-19 vaccines.
To sum up
♦ Vaccines provide acquired immunity against infectious diseases.
♦ Different stages of vaccine development: research, preclinical phase, clinical development, approval & licence, and post-licensure phase.
♦ Different approaches to vaccine design are: The whole microbial approach in which the organism or its components are used to prepare a vaccine; a subunit approach where the antigens are used; and a genetic approach, where the genetic material of the microbe is used.
Fathima Shameen, PharmD
FCPI Infectious Diseases Forum