The use of vaccines has led to major improvements in child and public health. With widespread use of vaccines, diseases like chickenpox, measles and polio no longer affect most children in the United States today.

As parents and caregivers, we want to make sure our children are healthy and protected from harm. Vaccination is one of the best ways to do just that. In fact, vaccines routinely given to infants, children and teens in the U.S. today protect them from 16 potentially harmful diseases.

Even so, many parents may have questions and concerns about vaccines, and that’s understandable. Our pediatric infectious disease expert Sean O’Leary, MD, MPH, explains the truth about vaccines based on scientific evidence: how they work and why they offer the best possible protection against serious and even deadly diseases.

How do vaccines work?

When a virus or disease enters the body, it’s the immune system’s job to identify the virus as a threat and fight it off. Vaccines are designed to train the immune system. They teach your child’s body how to protect itself so that if and when the real version of a disease appears, their immune system has already built the defenses it needs to fight the infection.

Are vaccines safe?

Yes, vaccines are heavily researched, constantly tested, and very safe. That is why when we’ve seen new viruses arise in recent years, it takes some time to develop a vaccine. And even once they are available to the public, they continue to undergo extensive testing.

Before a vaccine is available to the public, its safety and effectiveness must be thoroughly evaluated through clinical trials involving thousands of people. Physicians and scientists trained in dozens of disciplines review thousands of pages of data from these trials to evaluate and ensure the vaccine is safe and works well to prevent disease. The standard is even more strict for vaccines used in young children. And all vaccines continue to be monitored for safety by numerous scientific and medical institutions long after they are approved. The results of these extensive studies are clear.

“Vaccines are safe and effective,” says Dr. O’Leary. “The risks of not vaccinating far outweigh the negligible risk of reacting to the vaccine. For example, polio is no longer found in the United States — but it’s only a plane ride away.”

Still, it can sometimes be hard to tell what’s true and what’s not, especially with so much information out there that often seems to say different things. If you have concerns about vaccination, talk with your child’s doctor. They can answer questions to help you feel more confident about vaccines and their many benefits.

At Children’s Colorado, our experts speak with many families who have questions about vaccines, and there is a lot of uncertainty around current recommendations, vaccine availability and insurance coverage. As advocates for kids, science, and infectious disease research, experts at Children’s Colorado know vaccines to be safe. Vaccines help protect children against severe disease and should be available to families who are keeping up with routine childhood immunizations.  Multiple comprehensive studies have demonstrated no link between vaccines and other neurological and developmental disorders. 

The use of vaccines has led to major improvements in child and public health. With widespread use of vaccines, diseases like chickenpox, measles and polio no longer affect most children in the United States today. Some people do experience side effects from vaccines, such as soreness and fevers, and there are some rare vaccine injuries that occur. However, the benefits of vaccines — avoiding the diseases that vaccines prevent — make vaccination an important step in protecting your child’s health. 

Read more about vaccine research and monitoring or vaccine safety facts from The American Academy of Pediatrics (AAP).

Vaccine schedules give kids the best protection

Each year, top disease experts and doctors who care for children work together to provide evidence-based recommendations for vaccines and the AAP’s immunization schedule. The recommendations are based off the most recent scientific data available and are approved by the AAP and the American Academy of Family Physicians.

The scheduled vaccines are carefully selected to give children and teens the best protection at the best time. For instance, we vaccinate young babies because they are most vulnerable to disease in infancy. Vaccines are usually given during an annual well-child visit, so caregivers don't need to make a separate trip to their doctor or pediatrician to keep their kid up to date on their vaccinations.

Getting your child vaccinated on the recommended schedule is the best way to ensure they are protected from potentially harmful disease. Learn about the recommended immunization schedule from AAP.

Vaccines save lives and prevent disease

Vaccines protect against the spread of dangerous disease. They save millions of lives worldwide every year. However, not immunizing children puts them at risk of catching and spreading dangerous diseases, which puts other children at risk as well. In recent years, measles has started to pop up again in various communities. This highly contagious disease can be very dangerous and every time there is an outbreak, it is invariably spread through children who have not gotten a measles vaccine.

Vaccines work best when they protect the whole community, especially vulnerable people who are not able to receive vaccines or can’t easily fight off infections — like babies, the elderly and individuals with weak immune systems.

Most reactions from vaccines, such as a sore arm or slight fever, are minor and don’t last long. The diseases they prevent are often severe and can be fatal. Getting vaccinated is far better than getting the disease.

“Vaccinations are among the safest medical interventions we have,” Dr. O’Leary says. “They are a great gift we have to protect our children’s health.”

Vaccines for babies with medical conditions

Parents of babies in the Neonatal Intensive Care Unit (NICU) or with medical conditions have a lot to consider when it comes to their baby’s care. Their lives and treatment are just not as simple as many babies’. That’s true when it comes to infant vaccines, but the core truth about immunizations doesn’t change for these babies.

“We know that vaccines are critically important for all babies,” says Theresa Grover, MD, Medical Director of our NICU on Anschutz Medical Campus. “There is strong evidence that they prevent routine illness and life-threatening illness, and that is no different for premature babies.”

Why are vaccines for infants with medical conditions so important?

“Babies that are born prematurely are at higher risk of contracting diseases that are preventable by vaccines,” says Dr. Grover. “Their immune systems are less robust, and they are more likely to contract serious illnesses.”

Some vaccine-preventable diseases can even become life-threatening. Babies born prematurely respond well to immunizations, just like full-term babies. Dr. Grover says babies born in the NICU should get their full recommended vaccines at 2, 4, 6 and 12 months old. These vaccinations may take place in the NICU or during their first-year doctor visits. Vaccines are most effective when they’re given on time, so sticking to the recommended schedule is very important.

“Up to half of premature babies are under-vaccinated up to a year and a half after birth,” says Dr. Grover. “Sometimes it’s because the baby was severely ill in the hospital, so they didn’t get their vaccines on time. For those babies it’s important to work with their primary care doctor to make sure they get caught up on their vaccines.”

Special vaccine considerations for premature babies and babies with medical conditions

Most babies in the NICU should get their full course of vaccinations. But there are a couple considerations for specific vaccines.

Rotavirus vaccine in babies

Rotavirus is the leading cause of severe diarrhea in young kids, and the rotavirus vaccine is effective in preventing diarrhea. But the vaccine is not suitable for babies with severe intestinal conditions. Your child’s care team should tell you if your baby can’t receive the vaccine. You can also ask them any questions about rotavirus vaccine and your child.

Hepatitis B vaccine in babies

Normally, babies get a hepatitis B vaccine within the first 12 hours after birth. However, pre-term babies with low birth weight (under 2 kilograms or 4.4lbs) whose moms test negative for hepatitis B can instead receive their hepatitis B vaccine when they’re one month old or upon hospital discharge. Pre-term babies whose moms have a positive or unknown hepatitis B infection should receive a dose of the hepatitis B vaccine at birth regardless of birth weight to prevent infection.

If you have any questions about infant vaccines while you’re in the NICU, ask your care team or ask to talk with the NICU’s pharmacist.

Advances in vaccinations

Vaccines are constantly improving, and new vaccines are developed when new viruses become more widespread.

RSV Vaccine

The RSV vaccine is a new addition to traditional vaccines. RSV, or respiratory syncytial virus, is a disease that has become more widespread in recent years.

RSV is a very common virus in older children and adults, and frequently leads to the common cold. The disease can be very severe and has become the leading cause of hospitalization for young children. That is why it is so important to get infants vaccinated. There are many safe RSV vaccinations available now and even some that can be given before the baby is born.

Learn how to tell the difference between COVID-19, RSV, Flu and more.

HPV vaccine

HPV, or the human papillomavirus, is a very common disease spread by skin-to-skin contact, often during sexual activity. Most people get infected with HPV during their lifetime but are not always aware. While HPV may not be harmful to many, it causes about 30,000 cases of cancer every year, resulting in about 4,000 deaths. The disease is very preventable with a vaccine, and the ideal age for HPV vaccination is 11 to 12, but it can be given to everyone age 9 through 26.

Additional vaccine resources

Flu vaccine

Children’s Colorado, along with the American Academy of Pediatrics, recommend annual flu vaccines for all children older than 6 months.

Find a flu clinic near you.

COVID vaccine

Children’s Colorado, along with the American Academy of Pediatrics, recommend COVID vaccines for all children older than 6 months. We recommend getting your child’s first COVID vaccine between ages 6 months and 5 years. It is important to note that the younger the children, the higher risk they have regarding COVID. Children with chronic medical conditions are also at an increased risk. Similarly, adults older than 65 are also at higher risk of hospitalization if they contract COVID.

Learn more

Learn about the important work Immunize Colorado (formerly the Colorado Children’s Immunization Coalition) does to protect our Colorado community from vaccine-preventable diseases. Additionally, the American Academy of Pediatrics regularly updates its fact-checked resources page with updates about vaccines.