History
Vaccinations have been administered for hundreds of years. To prevent snake bites, Buddhist monks drank snake venom, and in 17th-century China, variolation—the application of cowpox to a skin tear to prevent smallpox—was done. When Edward Jenner vaccinated a 13-year-old kid with the vaccinia virus (cowpox) in 1796, the boy showed immunity to smallpox and is credited as being the first to develop vaccines in the West. In 1798, the first vaccination against smallpox was developed. In 1979, smallpox was completely eradicated thanks to the rigorous mass immunization program that took place during the 18th and 19th centuries.
The human inactivated anthrax vaccine and live attenuated cholera vaccine were created thanks to Louis Pasteur’s efforts (1897 and 1904, respectively). The late 19th century also saw the development of the plague vaccine.
Alexander Glenny developed the best way to use formaldehyde to render the tetanus toxin inactive in 1923. The creation of a diphtheria vaccine in 1926 followed the same process. The development of a pertussis vaccine took much longer, and the first whole cell vaccine was approved for use in the US in 1948.
The development of viral tissue culture techniques between 1950 and 1985 resulted in the development of the Salk (inactivated) and Sabin (live attenuated oral) polio vaccines.
Photo by: Dimas Ardian
For use in vaccines, attenuated measles, mumps, and rubella strains were created. Currently, measles is the next disease that could be eradicated by the vaccine.
Even though vaccination programs have been shown to improve health, some populations have always proved resistant to vaccines. There were fewer companies manufacturing vaccines in the late 1970s and early 1980s as a result of rising litigation and falling vaccine manufacturing profitability. In the year 1986 National Vaccine Injury Compensation program was launched in the US. The effects of this era may still be seen today in supply shortages and the persistent media campaigns of a vocal anti-vaccination lobby.
The field of vaccinology has benefited from the use of molecular genetics and its growing understanding of immunology, microbiology, and genomics over the past two decades. Recombinant hepatitis B vaccines, the less reactive acellular pertussis vaccine, and improved manufacturing methods for seasonal influenza vaccinations are examples of recent achievements.
Vaccines against all pathogens
Using the entire disease-causing virus in a vaccine to elicit an immune response akin to that seen during natural infection is the most traditional and well-known approach to immunization. The pathogen would produce active disease if used in its natural state, which could be dangerous for the recipient and increase the likelihood of the disease spreading. Modern vaccinations utilize modified microorganisms to prevent this.
Live-attenuated Vaccines
Live attenuated vaccines include entire bacteria or viruses that have been “weakened” (attenuated) to elicit a protective immune response without inflicting disease on healthy individuals.
Vaccines against all pathogens
Using the entire disease-causing virus in a vaccine to elicit an immune response akin to that seen during natural infection is the most traditional and well-known approach to immunization. The pathogen would produce active disease if used in its natural state, which could be dangerous for the recipient and increase the likelihood of the disease spreading. Modern vaccinations utilize modified microorganisms to prevent this.
Live-attenuated Vaccines
Live attenuated vaccines include entire bacteria or viruses that have been “weakened” (attenuated) to elicit a protective immune response without inflicting disease on healthy individuals. The majority of current vaccinations achieve this “weakening” of the pathogen through genetic change, either as a naturally occurring process or as a deliberate act.
The inactivated vaccines
Whole bacteria or viruses that have been destroyed or changed to prevent replication are present in inactivated vaccines. Inactivated vaccines do not contain any live bacteria or viruses, so even in those with highly compromised immune systems, they cannot spread the diseases they are intended to prevent. In contrast, live attenuated vaccinations tend to elicit a stronger and more durable immune response than inactivated vaccines.
Subunit vaccine
Subunit vaccinations, which don’t include any complete bacteria or viruses at all, make up the majority of the immunizations on the UK schedule. Instead, these vaccinations frequently include one or more particular antigens (or “flags”) from the pathogen’s surface. Subunit vaccinations provide an advantage over complete pathogen vaccines in that the immune response can concentrate on identifying a limited set of antigen targets (or “flags”), which helps prevent disease.
Subunit vaccinations frequently fail to elicit the same robust or durable immune response as live attenuated vaccines. Initially, they often call for repeated dosages, followed by booster doses the following year. Subunit vaccinations frequently have adjuvants added. These are elements that support and prolong the immunological response to the vaccine.
Recombinant protein vaccinations
Bacterial or yeast cells are used in the production of recombinant vaccines. The producing cells are given a small amount of DNA from the virus or bacteria that we want to protect ourselves from. For instance, a portion of the DNA from the hepatitis B virus is introduced into the DNA of yeast cells to create the hepatitis B vaccine. Once one of the hepatitis B virus’s surface proteins is produced by these yeast cells, it is purified and employed as the vaccine’s active component.
Subunit vaccinations, which don’t include any complete bacteria or viruses at all, make up the majority of the immunizations on the UK schedule. (The term “acellular” denotes the absence of complete cells.)
These vaccines instead comprise polysaccharides (sugars) or proteins that were found on the outside of bacteria or viruses. Antigens are the polysaccharides or proteins that act as the “foreign” antigens that our immune system detects. Even while the vaccine may only include a small portion of the bacterium’s hundreds of proteins, those few proteins are sufficient to start an immune response that can guard against the disease.
Toxoid vaccines
We want to be protected from the toxins rather than the bacteria themselves because some bacteria that attack the body release toxins (poisonous proteins). The immune system can build an immunological response to these toxins because it recognizes them in the same way that it recognizes other antigens on the surface of the bacteria. Some vaccines contain these poisons that have been inactivated. They cause the immune system to react strongly.
Conjugate vaccines
Conjugate refers to a connected or joined state. You must teach the immune system to react to polysaccharides (complex sugars on the surface of bacteria) rather than proteins to receive protection from a vaccine against some germs. However, it was discovered in the early days of polysaccharide vaccinations that they did not function effectively in infants and young children.
The polysaccharide performed far better when it was joined (conjugated) to a substance that elicits a robust immune response, according to research. The polysaccharide is typically joined to diphtheria or tetanus toxoid protein in conjugate vaccinations (see “Toxoid vaccines” above). These proteins are known to the immune system, which makes a stronger immunological reaction to the polysaccharide.
Nucleic acid vaccinations
Have you ever wondered what takes place inside your cells when a virus infects you? or the functioning of the new COVID-19 vaccines? How our cells receive instructions to create proteins provides the solution to these queries. Our cells resemble factories a little bit.
In contrast to conventional vaccines, nucleic acid vaccines don’t provide the body with the protein antigen, thus they operate differently. Instead, they impart the genetic code for the antigen to body cells, which then create the antigen and trigger an immunological response. Future vaccine development holds great promise thanks to the speedy and simple development of nucleic acid vaccines.
RNA vaccinations
mRNA, or messenger RNA, is used in lipid (fat) membranes in RNA vaccines. When the mRNA first enters the body, its fatty layer protects it. However, it also facilitates entry into cells by joining the cell membrane. The mRNA is translated into the antigen protein by internal cell machinery once it has entered the cell. Although this mRNA only persists for a few days on average, enough antigen is produced during that period to elicit an immunological response. The body then naturally breaks it down and eliminates it. RNA vaccines are unable to interact with the genetic code of humans (DNA).
Currently, the UK has approved the use of two RNA vaccines for emergencies. Both the Moderna COVID-19 vaccine and the Pfizer BioNTech vaccine are RNA vaccines.
DNA vaccinations
Because DNA is more durable than mRNA, it doesn’t need the same first defence. DNA vaccinations are frequently given combined with a process known as electroporation. This enables the body’s cells to absorb the DNA vaccination by using low-frequency electrical waves. Before DNA can be translated into protein antigens that trigger an immune response, it first needs to be translated into mRNA in the cell nucleus.
Although several DNA vaccines are being developed, there are currently no licensed DNA vaccinations.
Viral vector vaccines, like nucleic acid vaccines, are a more recent development. They work by employing unharmful viruses to transfer the genetic code of the target vaccination antigens to body cells, causing them to create protein antigens that trigger an immune response. Viral vector vaccines can be produced rapidly and easily on a wide scale since they can be generated in cell lines. When compared to nucleic acid vaccines and many subunit vaccines, viral vector vaccines are typically produced at significant cost savings.
