Vaccines - biological preparations that provide active acquired immunity to a particular infectious disease. Throughout history the development of vaccines has been at the forefront of medical advancement and hence have saved millions of lives from the ever newly developing pathogens. Nevertheless, the creation of these life saving drugs, encompass long periods of trial and error, before producing a marketable and effective antidote. The cause for the development of vaccines are one of two: the downfall or inefficiency of the drug proposed initially, or alternatively the discovery of a new or newly adapted pathogen.
The basic concept of how vaccines work is that they train the immune system to recognise and combat pathogens, so they act as enforcers of the natural human instinct to protect yourself from outside threats. More specifically, the vaccine imitates infection by containing the antigen of the disease, causing receptors on helper T cells to fit onto antigens, as non-self cells are detected. Subsequently T cells are activated to divide by mitosis to form clones of genetically identical cells. Cloned cells then develop into different cells: One such possibility being the development into memory cells that enable rapid response - an increased rate of production of antibodies, to future infections by the same pathogen. Another being, the division of B cells by mitosis and hence the secretion of antibodies, which in turn also develop into memory cells for secondary immune response.
Pathogens are ever developing and mutating, therefore there is a corresponding need for the antigen that is present in the vaccine to echo these changes, adaptations and developments. The most common vaccine being injected into around 165 million people globally per year, is the influenza vaccine. The influenza virus thrives at conditions of low temperature and low humidity, causing symptoms of fever, cough and fatigue amongst others, ultimately killing 290,000 to 650,000 people a year. Despite the virus having the potential to kill thousands more, the annual development of the influenza vaccine limits the mortality rate. It has become a custom that flu vaccinations are reviewed and updated annually, as the harming pathogens constantly mutate and hence triggering antigenic variability; consequently, the immune system has the inability to recognise newly adapted antigens. Previously produced memory cells were adapted to previous forms of the pathogen and hence will no longer respond to the developed antigens, making reuse of vaccine ineffective, as immunity would be short-lived. The annual adaptation of the drug is based on that year’s analysis of recent data, allowing scientists to identify new flu strains and hence to determine which of these is most likely to cause a spread of disease in the upcoming flu season. Thus, the commonly accepted misconception that having received the influenza vaccine once will protect the individual in future years is untrue and poses a risk to many.
There are however plentiful pathogens that still cause extensive harm to humans, to which vaccine developers, despite all medical advancement, have not been able to produce a countering vaccination. One of the most advanced types of vaccine technology is the DNA vaccine, produced and developed in recent decades. For decades, previous scientists relied on multiple approaches when developing contemporary vaccinations: the introduction of specific antigens against an immune system, which in turn reacts defensively being one, whilst also including the modified toxins of bacteria and weakened strain of pathogens. DNA vaccines alternatively, are used to stimulate cellular immune responses to protein antigens. This particular type of vaccine functions by directly introducing plasmids containing the DNA sequence which encodes the antigen into specific tissues, in response to which a defensive reaction from the immune system is sought. If the DNA sequence coding of an identified antigen can be inserted into a carrier genome, the host and hence the inserted DNA undergoes limited replication. Subsequently, this leads to the crucial protein that is needed being produced, hence the host’s immune response to the protein. Whilst there being theoretically functioning vaccines for Hepatitis B, Malaria and HIV, the use of DNA vaccines has been limited to veterinary purposes, due to pending approval for human use. Another modern type of vaccination are therapeutic vaccines. Conversely to any other vaccine on the market, these differ in that they can limit or even eviscerate an existing, established infectious agent. This vaccine is administered after the disease or infection has been contracted, therefore being applicable to HIV patients. To date a HIV vaccine has not been found, but there have been recent attempts to develop an HIV therapeutic vaccine, with the target of using activated T cells, to eliminate latent, infected cells through the induction of cytotoxic T cells. Moreover, Helicobacter Pylori - a bacteria that is known for causing stomach ulcers and stomach cancer in the digestive tract, has been studied extensively by scientists, in hopes of finding a therapeutic vaccine that can eradicate the bacteria in humans. Therefore, the dedication to the continuation of advancing and developing vaccines along with the ever developing technology provided to scientists, will eventually allow these now considered ‘potential vaccines’ to breakthrough onto markets, having a life-changing impact on millions of people.
In recent months the global pandemic has been the center of medical advancement, with numerous research centers spending millions of dollars and countless hours on attempting to develop a vaccination that will combat the killer that is covid 19. A prominent developer of futuristic vaccines has been Inovio - initially working on a DNA vaccine for Mers, but following the outbreak of covid-19 rapidly changing their focus to coronavirus. The vaccine developed targets major surface antigen Spike proteins of the virus; when tested on animals, high levels of Spike-specific T cell responses were recorded. Researchers have suggested a ‘human challenge trial’ - intentionally infecting healthy volunteers with the virus and subsequently injecting them with the trialled vaccine, which could potentially increase momentum of the clinical trials in process. Obstructing this however are the ethical issues entailed, due to the various unknown risks.
From the first vaccine created - the smallpox vaccine, to the newest scientific experimentation around finding a drug to allow 21st century society to combat covid-19, having already killed circa 421,000, the development of vaccinations has proven itself an extremely worthwhile and important aspect of the wide spectrum of medical advancement that is available to scientists in this age of technology.