Is autism linked to vaccines? Can I get vaccinated if I’m pregnant? How much is too much at one time? Answers to these questions and more.
To better understand the importance of vaccinations and to dispel some common vaccine myths, we hear from Dr. Buddy Creech, Director of the Vaccine Research Program at Vanderbilt Health.
How do we know vaccinations are safe?
Creech: Typically, vaccines are tested first in healthy adults so that we can make sure that the vaccines are safe and they make the type of immune response needed for the infection. Once we know their safety in healthy adults, we move to other groups, such as those with underlying health conditions, teenagers, children and eventually infants and toddlers.
In these studies, “safety” means people tolerate the vaccine well without major side effects. Every medicine can have mild side effects, and vaccines are no exception. We might see headache, tiredness, arm pain and even fever after vaccination, but these typically happen in less than 20-30% of people depending on the vaccine.
We also monitor for more severe side effects, including those we cannot see from the outside. In early studies, we test the function of the liver and kidneys, and we, check blood counts before and after immunization. We also follow study participants for at least 6 months, and typically one to two years, after their vaccination to make sure no new health issues have developed.
How are vaccines monitored?
Creech: Once a vaccine makes it through the rigorous process of clinical trials (which includes placebo-controlled trials), vaccine safety is monitored through a combination of active and passive surveillance.
Active surveillance means that during clinical trials and sometimes right after a vaccine is licensed, people are asked to report the side effects that they experience, such as headache, fever or arm pain.
For all vaccines, we also have passive surveillance, meaning that if a patient has a side effect, they can report this directly to the CDC Vaccine and Adverse Events Reporting System, which reviews these reports. They can also discuss the potential side effect with their health care provider.
At Vanderbilt Health, we have funding from the CDC to serve as the lead site nationally to help doctors and nurses make decisions about revaccinating patients who have had a side effect after a vaccine. There are also ways to use the electronic health records anonymously to look for any safety signals that health care providers or patients may not see in real time.
If there were a problem with the vaccine, how would the public be notified?
Creech: There are at least three ways that we have seen this happen. First, the CDC or FDA issues a health alert that a vaccine safety issue has been seen. Second, groups that guide the use of vaccines (for example the American Academy of Pediatrics) may update their recommendations and communicate these to the medical community and to parents. Third, the vaccine manufacturer may temporarily halt the use of a vaccine, depending on the severity or risk, though this is rarely needed.
Is there a link between vaccines and autism?
Creech: The idea that vaccines were connected with the onset of autism in children first came a paper published by a group of investigators in England. The lead author was Dr. Andrew Wakefield, and the paper included eight children.
Dr. Wakefield described children with autism spectrum disorder who also had stomach issues. When he biopsied the children, they seemed to have measles virus in their intestinal lining. The authors concluded that an abnormal immune response to measles may have led to both gastrointestinal (stomach and intestinal) symptoms and autism. The paper was seen as interesting until two things happened. First, it was realized that in at least one child, the symptoms of autism actually happened before the first dose of the measles, mumps, rubella (MMR) vaccine. Once that error was identified, the paper and the methods were examined more strictly. It was then found that Dr. Wakefield made up information and data for the study. His other authors retracted the paper since it was completely false, and Andrew Wakefield lost his medical license in the UK.
But because of this article, pediatricians, parentsand policymakers got worried. As a result, there have now been over 100 studies that include over 20 million children – and they show there is no link between vaccines and autism.
What vaccines are given during pregnancy? Aren’t there some that aren’t safe during pregnancy?
Creech: When you are vaccinating a mother, you get a two-for-one deal: You can protect the mother and the baby at the same time. Sometimes we vaccinate mothers because they are at increased risk of disease complications compared to non-pregnant women; influenza (flu) is a good example of this. Therefore, we provide the inactivated vaccine (but not the live version of the flu vaccine that is sprayed in the nose) during pregnancy, knowing that this protects both mom and baby.
We also want to protect the baby against pertussis until they can get their own pertussis vaccine. Therefore, with each pregnancy we give the tetanus, diphtheria and pertussis (Tdap) vaccine.
In addition to these two, we routinely recommend vaccination against RSV, a virus that causes infant pneumonia. Many women get the vaccine, while others wait to give an antibody against RSV to their infants.
There are a few vaccines that are live, weakened vaccines that we do not give during pregnancy. These include the measles, mumps, rubella (MMR) vaccine and the live influenza vaccine.
Can you receive too many vaccines at one time?
Creech: The human immune system is a remarkable thing. There is no way to overwhelm it or give too many vaccines at once. In fact, some vaccines may work better when given together rather than separately.
Two important things to remember: First, babies now receive far fewer components in vaccines than they did 50 years ago because we have changed how certain vaccines are made. For example, prior to the 1990s, babies might have received thousands of targets in a vaccine like pertussis; now, pertussis has been reduced to only four targets.
Maybe more importantly, every day our immune systems are assaulted by foods, air and environmental stimuli and can handle each very well. Therefore, we estimate that every vaccine given over the course of the first year of life is actually less than the number of immune stimuli that an infant receives daily.
Talk with your child’s doctor about immunizations
The Pediatric Primary Care program at Monroe Carell Jr. Children’s Hospital at Vanderbilt works to ensure quality care for your child as close to home as possible. This is our shared mission with community pediatricians, hospital partners, and the Vanderbilt Health family of pediatric clinics. Find a location near you.
