How the benefits of vaccines really compare to the risks
Few big choices come easy in parenting. What baby food to get, diapers to use or books to read can all feel like heavy decisions for first-time parents. But when it comes to weighing the pros and cons of vaccines, recommendations are much more straightforward, says Dr. Lindy McGee, a pediatrician at Texas Children’s Hospital and Assistant Professor in Pediatrics at Baylor College of Medicine.
“The data is very clear that the benefits of vaccination far outweigh the risks,” McGee says. Still, she knows parents might have questions or concerns about vaccines for their kids.
Here are some of the most common questions about the risks and benefits of vaccines and what research says about their safety.
What are the most common side effects of vaccines?
Like any medical product, vaccines can result in side effects, but they’re almost always minor, mild and temporary, McGee says. According to the U.S. Department of Health and Human Services, the most common vaccine side effects include:
Pain, swelling or soreness where the vaccine was given.
Feeling tired or achy.
Many of these reactions, however, are the result of the body’s own immune system kicking in and building immunity in response to the vaccine, and they should resolve themselves within a few days.
Reactions can vary, depending on the vaccine, McGee says, which is why every time you or your child get a vaccine in the U.S., the clinic gives you a Vaccine Information Statement (VIS). VIS sheets go over what research shows to be the risks associated with each specific vaccine, what to do if a serious reaction occurs and other info necessary for patients to give informed consent to get vaccinated.
Can vaccines cause serious side effects?
Just like people can be allergic to other pharmaceuticals like penicillin, it’s possible to be allergic to something in a particular vaccine. Serious reactions, however, are extremely rare, McGee says.
According to the American Academy of Pediatrics (AAP), life-threatening allergic reactions happen about once every million doses, appear within hours of getting vaccinated and can be managed in a healthcare setting. Serious reactions resulting in death are virtually unheard of.
Despite myths and misinformation circulating on social media, large-scale, peer-reviewed studies looking at vaccine safety haven’t found any link between vaccines and autism, autoimmune conditions, attention-deficit/hyperactivity disorder (ADHD) or SIDS.
How do the risks from vaccines compare to the diseases they prevent?
McGee says discussion about vaccine risk goes hand-in-hand with discussion on the risks posed by vaccine-preventable diseases.
The worst side effect that most people will experience after being vaccinated is a sore arm or fever. Measles, on the other hand, kills an estimated 100,000+ people every year worldwide, mostly young children. The Centers for Disease Control and Prevention (CDC) estimates that the flu caused over 410,000 hospitalizations last flu season and at least 24,000 deaths in the U.S. alone. When people with certain vaccine-preventable illnesses do survive, they can be left with life-altering health issues like intellectual disabilities, seizures and loss of sight or hearing.
When vaccination coverage rates drop, the risks of an outbreak go up. That's what happened in the U.S. in 2019 when declines in measles vaccination rates throughout the country led to the highest number of reported measles cases in more than 25 years.
When you take all this into account, risks from vaccine-preventable diseases are much worse than the risks posed by vaccines, says McGee.
How are vaccines tested for safety?
In order to be approved for use in the U.S., a vaccine has to be tested in three phases of clinical trials to ensure the vaccine is safe and effective, McGee says. By phase III clinical trials, the vaccine is tested in thousands of people against a placebo or another vaccine currently used in that age group to see how effective it is and what the side effects might be.
After a vaccine gets approved, multiple safety monitoring systems in the U.S. and other countries are set up to spot issues with a vaccine that might have been too rare to see in the clinical trials. Safety testing doesn’t stop.
Vaccines are only included in the recommended vaccination schedule as long as research shows the benefits outweigh the risks, McGee says. If at any point that changes, the vaccine is removed from the schedule and investigated further.
Can babies’ immune systems handle so many vaccines so early in life?
Yes, McGee says. In fact, while babies might get more vaccines than their parents or grandparents did (and are protected from more diseases), their immune systems don’t have to work any harder. That’s because advances in vaccine technologies have resulted in today’s vaccines having fewer antigens compared to those of previous generations.
Antigens are the parts or byproducts of a germ that the immune system reacts to. The more antigens your body is exposed to, the harder the immune system has to work, and the greater the chances of adverse reactions like fever.
According to the AAP, the vaccine schedule in 1960 contained a total of about 3,200 antigens. In the 1980s, it had about 3,000. But by 2000, that number had dropped to around 125 because some vaccines with a lot of antigens (like the DTP vaccine) were replaced with safer alternatives (like the DTaP vaccine) that had only a few antigens. McGee says that while there have been some additional vaccines added to the schedule since then, the total antigen count is still low compared to what kids received only a few decades ago.
Are there any benefits to spacing out vaccines?
While some parents wonder if spreading out vaccine doses would lower the chances of side effects, McGee says that doing so could carry different — and potentially much greater — risks.
“If you are spacing out vaccines, I cannot tell you which one to delay because that means you're taking on risk that your child could get one of these horrible diseases,” she says.
She adds that, unlike the vaccination schedule recommended by the CDC, there isn’t any research on how well these alternative vaccination schedules work or how safe they are.
McGee says that when a new vaccine is being developed, it’s tested with the vaccines that are already recommended for the same age group. That way, doctors and health officials can be sure that it would be safe and effective if it’s added to the vaccination schedule. If parents want to give vaccines at different intervals or in alternative combinations, McGee says we don’t know how well they would work or how safe they would be because those schedules haven’t been studied. The safest and most effective way to get vaccinated is by following the recommended schedule.
Are there people who shouldn’t get vaccinated?
Some people with specific medical conditions or life-threatening allergies shouldn’t get certain vaccines because the risks would be much higher for them.
For example, a 6-year-old from Sugar Land, Texas, named Juliana who was born with an inoperable congenital heart defect and had to receive a heart transplant when she was just 17 days old. The medications she takes help ensure her body doesn’t reject the new heart, but they also keep her from being able to safely receive some of the recommended vaccines, says Riki Graves, Juliana’s mom.
“It’s important that those around her are fully vaccinated,” Graves says. Because of Juliana’s condition, illnesses that would usually be mild in other kids could be especially dangerous for her.
Graves says everyone in the family gets all recommended vaccines, including annual flu shots, but they still have to rely on others in the community to stay up to date, too. She says that Juliana has already been hospitalized 19 times because of infectious illnesses, including one stay due to rotavirus, a vaccine-preventable disease.
For some parents, the choice to vaccinate is an easy one — not just for themselves, but also to protect kids like Juliana.
“I personally vaccinate my children because I trust the scientific data that shows us vaccines are safe and effective,” says Leah Roman, a public health consultant and mom of two in the Philadelphia area. “I vaccinate to protect my own children, but also to protect vulnerable people in my family and community.”