Have we found a safer and more effective way to create vaccines?
Without vaccines, the world would be a very dangerous place to live. According to the World Health Organization (WHO), vaccines have saved hundreds of millions of lives since they were first introduced to the medical world on May 14, 1796.
On that day, English physician Edward Jenner extracted fluid from a cowpox blister and scratched it into the skin of an 8-year-old boy. The boy developed an immunity to smallpox, a disease that up until that time killed millions of people every year. More advanced techniques for creating vaccines followed, and after a worldwide vaccination campaign, smallpox was eradicated, with the last naturally occurring infections recorded in the late 1970s.
From that first rudimentary vaccine, a new medical weapon against infectious disease was born. Today, vaccinations are estimated to save 105 million lives each year.
According to information published in the Journal of American Medicine, deaths due to tetanus, mumps, whooping cough and diphtheria have declined by 99 percent since the introduction of vaccines to protect against those diseases. Endemic cases of German measles, measles and polio have been eliminated entirely in the United States, and hepatitis A, varicella, Hib and hepatitis B infections and deaths have decreased by 80 percent.
“Vaccines are extremely important,” says Dr. Paul Gulig, a professor in the Department of Molecular Genetics and Microbiology at the University of Florida. “They have eliminated some infectious diseases, such as smallpox in humans and rinderpest in animals, and nearly eliminated others, such as measles and polio. They have also significantly reduced death and disease from countless others, such as tetanus, diphtheria, and the list goes on.”
Dr. Gulig says that the efficacy of vaccines for preventing disease is undeniable, and their importance goes far beyond the health of the individual who is inoculated.
“The nearly universal purpose of vaccination is prevention of disease in the person being vaccinated,” he says. “A person is vaccinated to prevent disease in case he or she is exposed to the pathogen at some point in the future. However, there are also great societal benefits. The most important is ‘herd immunity’. If enough people in a population are vaccinated and immune from infection and disease, then epidemics cannot take hold and even the unvaccinated people are protected. In every society, there are specific groups of people who cannot receive some vaccines, especially vaccines that are made of live organisms, such as measles, mumps and rubella. This group of persons must therefore rely on the rest of the population to protect them by herd immunity. If, for any reason, not enough people are vaccinated, then herd immunity fails. Witness the recent measles and whooping cough epidemics due to large populations of unvaccinated people.”
According to the Centers for Disease Control and Prevention (CDC), there are usually several measles outbreaks every year in the United States, and each occurs when the disease enters the country through an ill foreign visitor. The largest recent outbreak came in 2014 following a large outbreak in the Philippines. A high percentage of the American cases that year occurred in unvaccinated Amish communities in Ohio. In 2018, there were 11 reported cases of measles in Florida, with all 11 people contracting the disease being unvaccinated.
Dr. Gulig states that many times people shouldn’t be inoculated for valid medical reasons (such as a suppressed immune system), but many times parents also choose not to vaccinate their children because they feel that the vaccines aren’t medically safe. Scientists, in an effort to rid the world of major infectious diseases, have undertaken the daunting task of creating vaccines that will be safe and effective for all people.
“Traditional vaccines are primarily active vaccines, which means that a person is injected (although some can be given orally or by intranasal spray) with a component of the pathogen, and his or her immune system develops a response that protects that person from that pathogen,” he says. “There are also passive vaccines. A passive vaccination is when we are given antibodies that neutralize the pathogen or its toxins. Passive vaccines are given when there is not enough time for our bodies to develop a protective immune response after exposure (a few weeks). A good example of this is hepatitis A. If a person has not been vaccinated and is exposed, they could be administered human antibodies to the virus to prevent disease. Similarly, if an unvaccinated person begins to develop tetanus or diphtheria, both of which are caused by toxins in the body, the patient would be administered antibodies to neutralize the toxin and prevent further damage.”
Dr. Gulig says that traditional vaccines, some of which have been associated with rare adverse reactions in the past, are being replaced with new genetically engineered recombinant vaccines that are proving to be safer and more effective.
“At times, traditional vaccines may not be as safe as desired,” he says. “For instance, the polio vaccine mutant strain can, in rare circumstances, return to the virulent form. Here at the University of Florida, work is underway to create a recombinant polio vaccine that is safer because it will be engineered to never be able to cause disease. Recombinant vaccines, such as this one, are either organisms or products of organisms that are made by altering the genetic code of the organism or by getting other organisms to produce the vaccine component. The hepatitis B vaccine is recombinant because the gene for a part of the virus was cloned and expressed in yeast cells (safely and efficiently) for purification.
“Our ever-growing understanding of pathogenesis of infectious disease equips us with the ability to use recombinant DNA methods to create strains that are both safe and effective. As exemplified by the hepatitis B vaccine, this does not always involve live organisms. Often it involves producing the vaccine component in another organism in a safe and efficient manner. Another example of this is the diphtheria vaccine component in the infant vaccine to meningitis caused by Haemophilus influenzae type b. The diphtheria vaccine that we normally get is a chemically treated form of the toxin that is no longer toxic, so it is called a toxoid. The problem with chemical inactivation of toxins is that the toxin has to be treated sufficiently to prevent its toxicity, but too much treatment disables its ability to stimulate a protective immune response. In contrast, since we know precisely which part of the toxin is needed to produce its toxicity, we have mutated the gene in the exact spot so that the recombinant genetic toxoid is completely non-toxic yet stimulates protective immunity. Further, rather than purifying the toxin from the pathogenic bacteria, we can have harmless E. coli produce the toxoid for us.
“As we learn more about how bacteria and viruses cause disease and what type of immunity protects against disease, we become better equipped to use recombinant DNA technology to create vaccine strains that cannot cause disease but that induce a protective immune response. A recent example is cholera. By learning the details of how the bacterium Vibrio cholerae causes cholera, a vaccine strain was created by removing or mutating key genes that cause disease.
“One more example of a genetically engineered vaccine is a universal influenza vaccine. As you know, we must be vaccinated every year because the virus changes and immunity to last year’s virus doesn’t protect us this year. However, virologists have determined sites of the virus that do not change, and by engineering that specific component into a recombinant vaccine, we might be able to get people to make an immune response that will protect against influenza from year to year without the need to reformulate the vaccine every year.”
Dr. Gulig believes that these new recombinant vaccines are the wave of the future, and they will more effectively shield us from disease.
“The future for vaccines is extremely bright,” he says. “They are cost effective to society for preventing pain, suffering, death and economic loss. Also, there are many extremely serious diseases worldwide, such as malaria and tuberculosis, that are in dire need of new vaccines. As we learn even more about the detailed disease processes and the human immune response to infections, we can develop even safer and more effective vaccines. Recombinant vaccines are safer than the old ‘natural’ mutants or the chemically treated toxoids, and I believe that we will see an ever-increasing development of recombinant vaccines.”
Diseases Completely Preventable Through Vaccination
Rubella (German Measles): When pregnant women become infected with this virus, especially in their first trimester of pregnancy, it can cause miscarriage, fetal death, stillbirth or congenital rubella syndrome.
Diphtheria: This viral infection kills 5-10 percent of those who acquire the disease. In 2015, there were 4,500 cases reported worldwide, down from more than a million a year prior to 1980. This decrease is due to a worldwide vaccination effort.
Smallpox: This acutely virulent disease killed more people than any other disease in history, sometimes decimating entire villages and cities. Following a worldwide vaccination campaign, smallpox was completely eradicated. The last known natural case was in 1977.
Polio: There is no cure for this highly contagious disease that affects mainly children and young adults. It affects the nervous system and can cause paralysis.
Pertussis (Whooping Cough): This upper respiratory disease that is most dangerous to infants causes paroxysmal coughing spells and frequently leads to pneumonia. The World Health Organization estimates that a worldwide vaccination campaign against the disease in 1980 prevented 687,000 deaths.
Source: World Health Organization, who.int