Experimental vaccines
Experimental vaccines are vaccines that have not yet received official approval for medical use and are currently undergoing clinical trials to assess their safety and efficacy. While some experimental vaccines successfully elicit an immune response, others may fail to do so or may present unacceptable risks compared to their potential benefits. The history of vaccination dates back to Edward Jenner's smallpox vaccine in 1796, which laid the foundation for modern immunology and has significantly influenced public health. Today, researchers are actively developing experimental vaccines for various diseases, including malaria, HIV, tuberculosis, and COVID-19, employing innovative methods such as mRNA technology.
The process of developing these vaccines poses significant challenges, as it often requires extensive testing to ensure volunteer safety and informed consent. Recent advancements, particularly during the COVID-19 pandemic, have led to rapid progress in vaccine development methodologies. Experimental vaccines may also target specific cancers and drug addictions, showcasing the breadth of ongoing research in this field. As scientists continue to explore new avenues for immunization, the potential impact of successful experimental vaccines could transform healthcare and enhance global health outcomes in the future.
Experimental vaccines
- ALSO KNOWN AS: Candidate vaccines, trial vaccines
Definition
Experimental vaccines are those vaccines that have yet to be officially approved for medical use. By definition, many experimental vaccines are never approved. Some simply do not produce an immune response, some produce a response that is too weak, and some have serious side effects that researchers consider too risky when compared with the possible benefits of the vaccine.
History
The first experimental vaccine of the modern era was English physician and scientist Edward Jenner’ssmallpox vaccine. Jenner observed that people infected with cowpox developed a mild illness but never developed smallpox, a common infection that had killed millions throughout history. In 1796, Jenner used pus from a milkmaid infected with cowpox to inoculate an eight-year-old boy. He later inoculated the boy with smallpox, and no illness ensued, proving his vaccine was successful. From such a modest beginning sprouted a medical revolution that added years to the human lifespan. The list of diseases against which a successful vaccine has been developed is long, but some of humanity’s biggest scourges are not on this list.
Vaccines against malaria, hepatitis C, tuberculosis, the human immunodeficiency virus (HIV), and COVID-19 are some of the most sought-after vaccines in the twenty-first century. (A vaccine exists for tuberculosis, one that has been in use for decades, but its effectiveness is unclear, and its use is controversial.) For each of these diseases, several experimental vaccines are in clinical trials and more experimental vaccines remain in development. However, the specifics of each disease present practical challenges that make the development and testing of new vaccines difficult, lengthy, and expensive. For example, the malaria parasite spends little time in the bloodstream once it invades the human body; most of the parasite’s development occurs in the liver. Because of this, developing a vaccine that will activate the immune system before the parasite gets into the liver, where it spends most of its time, was an ongoing challenge.
In addition to looking for vaccines against infectious diseases, researchers continually look for ways to develop vaccines against specific types of cancers, such as melanoma (a particularly deadly form of skin cancer), and for vaccines that target specific drug addictions (to cocaine and nicotine, for example). The success of this research is apparent in the development and widespread, successful use of the human papillomavirus (HPV) vaccine, which prevents infection of the virus which causes cervical cancer. In the developing vaccine field, researchers are also trying to develop therapeutic vaccines, those vaccines given to people who are already sick, in an attempt to reduce both the severity of the illness and the risk of transmitting the illness to others.
In 2020, the development of COVID-19 vaccines began at an unprecedented rate, and despite some skepticism, the vaccines proved to be successful in lowering the severity of the illness and decreasing death rates attributed to the virus. The methods used to develop mRNA vaccines were noted in 2022 to be revolutionary for all vaccines, as they are safe for immunocompromised patients, can be quicker to produce than vaccines with live strains of the virus, and are cost-effective. In the 2020s, research, development, and experimental trials concerning the treatment and prevention of several illnesses remained underway using this method, including—Ebola, Zika, Lyme disease, HIV, influenza, and some types of cancer.
Many scientists adjusted their approach to experimental vaccines following the COVID-19 pandemic, and positive discoveries continued to emerge. In 2021, the World Health Organization officially recommended Mosquirix (RTS,S/AS01), a malaria vaccine. In 2023, a second vaccine, R21/Matrix-M, was recommended. In 2024, Penn Medicine scientists created an experimental mRNA avian flu vaccine.
Testing and Trials
Jenner’s method of testing his vaccine would be considered criminal in the modern world. However, not until the latter half of the twentieth century did the concept of protecting the rights of people in medical research emerge. The concept emerged slowly, but it gained momentum after World War II and even more so when evidence of serious abuse came to light.
Participating in modern clinical studies of experimental vaccines must be voluntary. Before any volunteers are allowed to participate in a trial, the suggested trial procedure is reviewed by several regulatory and ethics committees. These reviews are designed to ensure the trial is safe and that volunteers are sufficiently informed of the possible dangers of the trial before they agree to participate. Volunteers also must meet strict health criteria to participate in vaccine trials.
Experimental Methods of Creating Immunity
Many of the ailments for which vaccines are sought present special challenges for researchers. For example, a weakened form of HIV as a vaccine cannot be administered because of the risk that the virus will reappear at full strength. Researchers hope to create an immune response through several novel methods that do not involve using the entire organism.
One experimental method has been the insertion of some genes from a dangerous virus (such as HIV) into a weakened virus, such as a cold virus, that is known to be relatively safe in humans. When the administered weak virus forms in the body, it forms with some of the proteins of the dangerous virus. Researchers hope the immune system in such cases will learn to recognize these proteins as foreign and will then mount an attack against the dangerous virus if it infects the body. Another experimental method involves, first, identifying the proteins on the surface of a microorganism that produce an immune response and then, second, vaccinating a person with these proteins alone (instead of the whole virus) to produce an immune response.
Impact
Vaccines have played a significant role in bettering human health and prolonging human life. The dreaded childhood diseases of the past, especially of the time before vaccines, no longer claim or maim thousands of young lives each year. All vaccines began as experimental vaccines. As technology advances, and as the understanding of the immune system increases, researchers are taking on bigger, more complex challenges and testing vaccines that could revolutionize medicine for generations to come.
Bibliography
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