Understanding Vaccines
A user-friendly guide to the most powerful tool in medicine
From smallpox to chickenpox, Ebola virus to influenza, how have vaccines against infections like these changed the course of human health? How do vaccines work and how concerned should one be about side effects? Welcome to your user-friendly guide to vaccines, where we help separate fact from fiction and offer a closer look at how Texas Biomed is at the forefront of vaccine development.
Millions of people today are alive and well because of vaccines and the protection they provide against harmful germs. The numbers are massive and can be hard to visualize: 150 million children saved since 1974 thanks to childhood immunizations; nearly 94 million children did not die because of measles vaccines; 20 million people have not been paralyzed by polio because of polio vaccines; 20 million deaths were averted in the first year of the COVID-19 pandemic due to COVID vaccines; the list goes on.
Simply put, vaccines are the most powerful tool in medicine. By bolstering your natural immune defenses, life-threating illnesses become non-life-threatening. Nothing has done more, alongside basic hygiene and sanitation practices, to stop the spread of germs and improve human health. However, misinformation about vaccines is on the rise, which can cause confusion. Many illnesses that once all but guaranteed parents would lose a child before the age of five have become a distant memory in many parts of the world thanks to vaccines. This makes it harder to directly appreciate the benefits of standard immunizations.
Polio outbreak in the 1950s in the US: Children paralyzed from the neck down by polio had to stay in iron lungs that helped their lungs expand and contract so they could breathe. Polio has largely been eradicated around the world thanks to vaccines.
Credit: Science History Images/CC
“We made it through our first months of life because our parents, aunts and uncles were vaccinated against things like whooping cough and smallpox, which protected us as babies until we could get vaccinated,” said Texas Biomed President/CEO Larry Schlesinger, M.D. “We want to help educate our community about how safe and effective vaccines are, while addressing the questions many have about them.”
The following guide offers a user-friendly overview of how vaccines work, answers frequently asked questions and plainly addresses some concerns about vaccines. It also aims to demystify the research and development process and highlight how Texas Biomed is working to advance vaccines against a range of diseases, from Ebola virus to tuberculosis, COVID-19 to influenza.
How vaccines work
Vaccines help strengthen your immune system against invading germs that can make you sick. Receiving a vaccine presents your body with a watered-down version of a harmful bug, such as a virus or bacteria. This gives your immune system a chance to develop specialized defenses against the bug without you getting seriously ill. That way, if you encounter the real thing, your immune system is primed and ready to respond. You will typically experience a much milder illness or none at all.
The idea is that you would never want to go into a battle or athletic contest unprepared. You’d practice and wear appropriate gear and protection. Same goes for facing the wide array of microorganisms that we are routinely exposed to and that make us sick. And vaccines are the most winning strategy out there.
Some vaccines provide total protection, while others dramatically reduce the chance of severe illness and the need to go to the hospital.
Vaccines are especially good at ensuring children survive their first year of life. In 1974, about 10% of infants didn’t make it to their first birthday. In 2024, that rate has dropped to 3%.
Vaccines are especially good at ensuring children survive their first year of life as their immune systems are getting up to speed. In 1974, about 10% of infants didn’t make it to their first birthday. In 2024, that rate has dropped dramatically to 3%. In those 50 years, an estimated 154 million children did not die thanks to vaccines, according to an analysis in The Lancet. The measles vaccine has had the largest positive impact on children, having saved an estimated 93.7 million lives.
Starting with smallpox
The first vaccine was against smallpox. In 1796, an English physician, Dr. Edward Jenner, inoculated an 8-year-old with a related, but milder cowpox virus, which completely protected the child against an exposure to smallpox. For thousands of years, smallpox was one of the world’s deadliest infectious diseases, killing at least 1 in 3 people infected. In 1980, thanks to international collaboration, smallpox was declared eliminated worldwide and vaccines are no longer needed.
Vaccines have been developed against a range of diseases, from typhoid to rabies, influenza to yellow fever. Polio vaccines were developed in the 1950s and are credited with helping to nearly eliminate polio viruses worldwide. Only one strain still remains in Pakistan and Afghanistan. Polio is caused by a highly infectious virus that attacks the nervous system. Historically, one in 200 infections led to paralysis. More than 20 million people are walking today who would have been paralyzed by polio had it not been for vaccines, according to the World Health Organization.
Measles used to kill 2.6 million people a year before the vaccine was introduced in 1963. Most deaths were related to complications from the disease – brain swelling, severe dehydration and interfering with the immune system so the body can’t defend itself against other infections, leaving children especially vulnerable. The measles vaccine is credited with avoiding 60 million deaths between 2000 and 2023, according to the World Health Organization.
Measles used to kill 2.6 million people a year before the vaccine was introduced in 1963.
Other routine immunizations are for infectious diseases that we don’t hear much about any more like diphtheria, which is part of the DTaP vaccine that also covers tetanus and pertussis (also known as whooping cough). In the 1920s, diphtheria caused 200,000 cases a year in the U.S. That number has dropped 99.9% thanks to vaccines.
Who remembers chickenpox?
Readers born before 1995 will likely remember getting chickenpox in grade school – itchy! For those who went through that rite of passage, it is hard to believe that kids don’t have to now – and haven’t for 20 years thanks to the chickenpox vaccine. That is a good thing for a couple of reasons. There is the immediate benefit of avoiding chickenpox itself – no insatiable itching, no missed school and sports, no disgusting and questionably-soothing oatmeal baths and potential scarring. The arguably bigger benefit: preventing shingles, which is a reactivation of the same virus later in life, which causes a painful rash and even nerve damage.
Viruses can lie dormant in the body for a long time and then contribute to a range of other illnesses, including cancer and neurodegenerative diseases. For example, human papillomavirus (HPV) is now recognized to cause a variety of cancers. Once the HPV vaccine was introduced in 2006, cervical cancer rates dropped precipitously in areas of the world with higher immunization rates. For example, among women under 25 in the U.S., cervical cancer deaths dropped by 62% from the 1990s to 2021.
The links between infectious diseases and chronic illnesses like cancer and neurodegenerative diseases are becoming increasingly clear. As just one example, Dr. Larry Schlesinger’s oral cancer was linked to HPV, one of the most common viruses people get.
On a more personal note, Texas Biomed President/CEO Larry Schlesinger was diagnosed with oral cancer linked to human papillomavirus (HPV), which was treated and currently he has no evidence of disease. There was no vaccine when he was growing up. If there had been, he likely would have been spared from a battle with cancer. Most people get HPV without realizing it. Not all will develop an HPV-related cancer, but it underscores the strong link between infectious diseases that are transmissible and “chronic” conditions like cancer.
Developing vaccines at Texas Biomed
Texas Biomed researchers work on a range of tools to improve human health, including new diagnostic tests, therapies like antibody cocktails and host-directed immunotherapies, and preventative vaccines. Developing a new therapy or vaccine can typically take 10 to 15 years: this includes everything from early, fundamental research through numerous testing phases in the lab and in people, regulatory reviews and production. (Learn more about COVID-19 vaccines in the FAQs.)
Several Texas Biomed scientists specialize in the early phases of research and development of vaccines, including fundamental studies about viruses, bacteria and parasites that cause illness, designing new vaccines to protect against them, and conducting preclinical tests to determine if a vaccine is safe and effective before they go to people. They test vaccines for external collaborators as well as design new vaccines. Here is a snapshot of some of the vaccines innovated at Texas Biomed that are working their way through the research and development process.
TB vaccine | Deepak Kaushal
For the past 15 years, Dr. Kaushal has been working to develop a more effective tuberculosis (TB) vaccine. The only licensed TB vaccine on the market, the Bacille Calmette-Guerin (BCG) vaccine, was developed more than 100 years ago and has limited effectiveness in adults. Dr. Kaushal’s delta sigH vaccine aims to improve protection against one of the world’s leading killers. It currently is going through preclinical testing at Texas Biomed.
What makes it different: BCG is based on the TB bacteria that infects cows, while delta sigH is a weakened, or attenuated, version of the bacteria that infects humans. In head-to-head studies with BCG, the delta sigH vaccine elicited a much more balanced immune response that reduced inflammation and harmful scarring in the lungs, enabling better control and elimination of the bacteria.
“We have recently completed safety studies to meet international standards for live-attenuated vaccines,” Dr. Kaushal said. “Studies are also ongoing to determine how long protection lasts and if effectiveness varies when given as a shot compared to delivered directly to the lungs. Once we have those insights, we are optimistic we can move forward to human clinical trials in the coming years.”
HIV vaccine | Marie-Claire Gauduin
For nearly 15 years, Dr. Gauduin has dedicated her work to developing an innovative HIV vaccine. Currently there is no vaccine to protect against HIV; developing one is incredibly challenging because the virus mutates and is very good at hiding from the immune system. Dr. Gauduin’s mucosal vaccine focuses on stopping the virus at the most likely point of entry: the fragile inner lining of the vagina and rectum. It is currently in preclinical testing at Texas Biomed.
How it works: Imagine the body’s mucosal lining — the moist surfaces in places like the nose, mouth, vagina and rectum — as the front gate where viruses first try to sneak in. This vaccine trains the body to make antibodies and protective cells in the mucosal lining. Much like a bouncer checking for fake IDs just inside the door or sentries along a castle wall, these antibodies and immune cells are well positioned to quickly respond and stop the virus the moment it shows up, before it can move deeper into the body.
“What makes this approach special is that we target the very foundation of the lining, called the basal layer,” Dr. Gauduin explained. “That layer is like the seedbed that grows all new cells. By reaching it, the vaccine ensures that every new cell carries protection. This way, the defense doesn’t just work once — it renews itself over time.”
Lassa virus vaccine | Luis Martinez-Sobrido
Dr. Martinez-Sobrido has been developing Lassa virus vaccine candidates for the past 10 years with collaborators at The Scripps Research Institute. The team has recently developed a live-attenuated vaccine, which includes a weakened version of the virus, that was 100% effective in preclinical tests in guinea pigs. The vaccine is proceeding to the next phase of preclinical testing in larger animal models at Texas Biomed.
The threat: Lassa virus, which has no vaccine nor treatment, has an estimated fatality rate of 15-20%. While many people have no symptoms, the virus can cause fever, severe bleeding and organ failure within two weeks of infection. Found throughout Western Africa, Lassa fever is a priority disease for vaccine research and development according to The World Health Organization because it presents a high potential for a public health emergency.
“A live-attenuated vaccine can offer longer-lasting and broader protection because now your body’s immune system is being trained to recognize the entire virus—not just one small piece of it,” Dr. Martinez-Sobrido said.
Universal flu vaccine | Luis Martinez-Sobrido
Rather than the annual flu shot, Dr. Martinez-Sobrido is working on a universal flu vaccine that provides long-lasting protection against influenza. He is incorporating multiple virus strains into one live-attenuated vaccine, prompting a broader and more robust immune response. The vaccine is currently in early stages of research and development at Texas Biomed and supported by funding from the American Lung Association.
The challenge: Influenza viruses are notorious for mutating – a lot. That is why seasonal flu shots must be updated annually and vary in effectiveness; it is difficult to pin down which strains to target far enough in advance to complete the production process in time. Seasonal flu shots are based on inactivated, or killed, viruses, which do not elicit as strong of an immune response. Dr. Martinez-Sobrido’s live-attenuated vaccine is based on a “single-cycle virus” that is engineered to replicate once but cannot produce infectious virus inside the body.
“This combination makes it more effective than current inactivated vaccines and safer to use compared to other live-attenuated vaccines,” Dr. Martinez-Sobrido said.