Types of Vaccines
Vaccines have indeed revolutionized the way diseases are prevented. During the 20th century, significant achievements have been made in public health and as such, there was a dramatic decline in the reported cases of vaccine-preventable diseases while some were even totally eradicated. The introduction of safe, affordable and effective vaccines saved millions of people and are now enjoying longer and healthier lives.
Current vaccines today are developed through different techniques and it usually involves antigen discovery. They are typically composed of either the inactivated disease-causing microorganisms or purified products and may be classified into several types:
Live Attenuated Vaccine:
Live attenuated vaccines are designed to cause an infection without exhibiting any symptoms. The infection would trigger an immune response but without causing any illness and without spreading onward to infect other individuals. Live vaccines can be made for either viruses or bacteria, but more commonly for viruses because they contain lesser genetic material and can be controlled more easily. In order for a virus to be considered for the formulation of a live vaccine, it must be first capable of growing in vitro. The selected virus is then grown repeatedly through successions of cell cultures to weaken it so that it is no longer able to replicate in human cells. Examples of live vaccines produced were derived from measles, rubella, mumps, and chickenpox.
One of the earliest vaccines to be developed, the inactivated vaccine is produced by “killing” the microorganism with the use of heat, radiation, or chemicals. The microorganism is no longer capable of causing illness but can still trigger an immune response. This type of vaccine is only effective for a shorter period of time and usually, several doses or multiple boosters are required to achieve a highly effective immune system. Examples of inactivated vaccines are Poliovirus and Hepatitis A.
Conjugate vaccines are derived by conjugating carbohydrates from a pathogen with a carrier protein. Together they both create a more effective immune response and can protect the body from future infections of the disease. Vaccines produced against pneumococcal bacteria are an example of conjugate vaccines.
Vaccines against harmful toxins released by some bacteria are produced by inactivating or weakening the toxins using heat or chemicals. A vaccine against tetanus which is caused by the neurotoxin of Clostridium tetani is an example of toxoid vaccine.
Rather than introducing inactivated or killed vaccine into the host, only a portion of the microorganism is needed to elicit an immune response. This may be done by isolating a protein from the pathogen and present it as antigens on its own. For example, influenza vaccines are developed using the proteins from the surface of the virus.
Whilst current vaccines have hugely improved the quality of life, vaccines have yet to be developed for many diseases. Most vaccines used today are produced using technologies that were pioneered more than a century ago thus, full potential of vaccine technology has not yet been achieved. However, rapid advancements in science and technology have led to innovations in the development of vaccines. Laboratory skills and techniques involving the use of PCR, mass spectrometry, bioinformatics, next-generation sequencing (NGS), protein engineering, and immunotherapy enabled several innovative vaccines to emerge in the 21st century.
DNA vaccines typically consist of DNA molecules that are directly administered to a patient. They can be controlled with a needle and syringe or with a needle-less gadget that utilizes high-weight gas to shoot gold particles covered with DNA straight into the cells.
RNA vaccines, on the other hand, are another promising type of vaccine that directly inject RNA molecules encoding the information to produce antigen in the host. The antigen would then trigger an immune response.
The advent of recombinant DNA technology fueled advancements in vaccine research and development. The use of recombinant viruses has been regarded not only as a promising means of inducing immunity but also to improve conventional vaccines and develop new ones.
A weakened virus is usually utilized as a “vector” wherein it functions as a carrier of the DNA sequences that encode for immunogenic proteins from other microorganisms . When introduced to the host the virus would lock on to cells and infuse their genetic material into them.
Synthetic vaccines are comprised of synthetic versions of identified protein sequences assembled to imitate the virus causing disease. Since synthetic vaccines basically do not contain any genetic material they would pose practically less or no risk of contamination by toxic or pathogenic substances. Also, they can be intended to evoke an immune response on the actual pathogen with more accuracy and reliability than the vaccines containing the whole microorganism.
Dendritic Cell Vaccines are primarily used as a form of immunotherapy to treat cancer. Dendritic cells are a type of immune cells whose role are to identify, handle and present foreign antigens to T-cells in the effector arm of the immune system. Albeit considered as powerful cells, they are not normally present in adequate enough amounts to illicit an immune response. Typically a dendritic cell treatment would include the collection of platelets from a patient to be processed in the lab to create a huge amount of dendritic cells. The processed dendritic cells will then be delivered back to the patient in order to fully activate the immune response.
The VacciXcell Advantage
VacciXcell offers a complete range of equipment suited for the development of vaccine starting from the research and development stage until the production scale. CelCradle™ and TideCell® bioreactors utilizes the tide motion principle, wherein cells residing in the matrix vessel are alternately exposed to aeration and nutrition via oscillation of culture medium. CelCradle™ is a highly recommended bioreactor that is capable of high-density adherent cell culture . It has the advantage of having low shear stress, foam-free environment, and no oxygen limitation. The TideCell®, on the other hand, is a production scale bioreactor that is linearly scalable up to 5000 L with a closed, automated and controlled cell harvesting
A. H. (2015, May 05). RNA vaccines: A novel technology to prevent and treat disease. Retrieved September 21, 2016.
Alexandra Minna Stern and Howard Markel The History Of Vaccines And Immunization: Familiar Patterns, New Challenges Health Affairs 24, no.3 (2005):611-621
"Different Types of Vaccines." http://www.historyofvaccines.org/content/types-vaccines Retrieved. 20 Sept. 2016.
Hajj Hussein, I., Chams, N., Chams, S., El Sayegh, S., Badran, R., Raad, M., … Jurjus, A. (2015). Vaccines Through Centuries: Major Cornerstones of Global Health. Frontiers in Public Health, 3, 269. http://doi.org/10.3389/fpubh.2015.00269
“Types of Vaccines”. (n.d.). http://www.vaccines.gov/more_info/types/#recombinant Retrieved September 21, 2016.
Vaccine Factbook 2013