The first vaccine ever made, created by Edward Jenner, was for smallpox. Smallpox is caused by the variola virus. Once infected, people experience fevers and body aches followed by an initial rash that develops into pus-filled sores. Smallpox is highly contagious and fatal; about 30 percent of smallpox infections resulted in mortality.
This deadly disease killed 300 to 500 million people from 1914 to 1977, according to the Centers for Disease Control and Prevention (CDC). Though Jenner created the vaccine in 1798, smallpox was not deemed eradicated by the World Health Organization until 1979. A number of factors aid in the eradication of a disease through vaccination; including costs, availability, political will and, most importantly, adoption by the public.
Vaccinations, also known as immunizations, significantly reduce disease, death and disability worldwide. Most often, vaccines are regarded as the single most significant medical breakthrough of the 20th century. However, in recent years an anti-vaccine movement has emerged, leading many to question the necessity of vaccination. Perhaps the public’s fear of vaccines can be attributed to a lack of understanding of how vaccines are created. Truthfully, vaccine development is a complex process that is rigorous and thorough, leaving little reason for public wariness.
Viruses are small non-living agents that replicate inside of hosts cells. They infect a number of hosts, such as plants, animals, and bacteria. Most immune systems are strong enough to detect virus invasion, suppress viral replication, and eventually kill any cells that may harbor viral particles. However, some viruses are lethal and cunning and able to evade major components of the immune system, which leads to severe disease and/or death.
Most viruses enter human hosts through a mucosal-lined surface, like saliva in the mouth or body fluid around the genital area. The need for a host cell is imperative to the objective of any virus, which is replication. This process can only start and continue inside a host cell. Once viruses find an entryway they override the natural cells processes and use them for producing more virions or virus particles. These virions then spread from cell to cell, possibly killing the cell to do so.
For example, Human Immunodeficiency Virus (HIV), infects vital immune cells such as CD4+ T-cells, replicates inside the cell, and kills the infected cell by directly bursting through the cell’s membrane, initiating cell programmed death, or indirectly allowing recognition by other cell killing immune cells. Thusly, HIV infection leads to low levels of CD4+ T-cells, which makes the host more susceptible to other infections and could lead to Acquired Immunodeficiency Syndrome, also known as AIDS.
The purpose of a vaccine is to strengthen the immune system’s ability to detect and attack any future viral infection. Vaccines provide a way to protect the health of a vast majority quickly and effectively. Scientists aid in vaccine development by searching for viral elements that either elicit a host immune response or are required by the virus to survive inside the host. This research is then used to inactivate or weaken infectious virus for vaccine use.
For example, each year the influenza vaccine either contains a live, attenuated virus (a less virulent virus) or an inactivated or dead virus. Vaccine development begins in January by identifying the top three disease causing strains of flu. These three strains are injected into fertilized chicken eggs to combine the genetic material of each strain and then the virus is inactivated and packaged for use in October.
To create an attenuated or weakened virus, scientists identify harmful viral elements, or antigens within the genetic material of the virus. This process is not easy. Viruses contain a number of genes and proteins and many of them may not be important or necessary for viral entry, replication, or pathogenesis. It may take researcher years (or decades) to isolate, identify, modify or characterize a gene or protein of interest.
Once identified and characterized, harmful disease-causing genes are removed from the virus and then the newly modified virus is used to infect cells or animals. Lastly, the pathogenicity, or harmfulness of the altered virus, is compared to the original virus. Scientist works for years to effectively manipulate a virus so that it maintains key viral components, which would allow detection by the host immune system, yet no longer has many of its top disease-causing parts.
Once the influenza vaccine is injected (inactivated virus) or inhaled through the nasal spray (attenuated virus), white blood cells in the immune system detect the virus, develop antibodies against the virus, and begin to create a “memory”. So, if the virus represented itself the body would be ready to attack before you develop an illness or related symptoms. Once a person receives a vaccine, it takes about two weeks for the body to build immunity. If a person were exposed to the flu within the two-week window, they could still get infected.
The idea of exposing oneself to a live, attenuated virus is not an easy sale to most. As with any vaccine or drug, our bodies respond differently and unintended consequences do arise from using a vaccine. There may be side effects, such as a runny nose or moderate to high fever. However, tens of thousands die from influenza, on average, each year. Thus far, the worst flu season was 2003-2004 with an estimated 48,614 influenza-associated deaths, according to the CDC.
But, diseases that used to be rampant have been significantly reigned in by vaccinations. Each year, more than 3.5 million cases of the chicken pox virus, 9,000 hospitalizations and 100 deaths are prevented by vaccination in the United States, according to the CDC. In 2012, there were 122,000 measles deaths globally, according to the World Health Organization. But, measles vaccinations resulted in a 78 percent drop in measles deaths between 2000 and 2012 worldwide.
Vaccine development and regulation has evolved since the first smallpox vaccine by Edward Jenner. As the scientific community continues to investigate ways to stop disease-causing pathogens and manufacture vaccines, it becomes imperative that we open dialogue with the public to alleviate their fear of vaccines. Better understanding of the meticulous vaccine development process could be key to wider vaccine adoption by the public.