Vaccine Safety

Question: Are vaccines safe?

Yes. Vaccines are very safe. The United States’ long-standing vaccine safety system ensures that vaccines are as safe as possible. Currently, the United States has the safest vaccine supply in its history. Millions of children safely receive vaccines each year. The most common side effects are typically very mild, such as pain or swelling at the injection site.

What are the risks and benefits of vaccines?

Vaccines can prevent infectious diseases that once killed or harmed many infants, children, and adults. Without vaccines, your child is at risk for getting seriously ill and suffering pain, disability, and even death from diseases like measles and whooping cough. The main risks associated with getting vaccines are side effects, which are almost always mild (redness and swelling at the injection site) and go away within a few days. Serious side effects after vaccination, such as a severe allergic reaction, are very rare and doctors and clinic staff are trained to deal with them. The disease-prevention benefits of getting vaccines are much greater than the possible side effects for almost all children. The only exceptions to this are cases in which a child has a serious chronic medical condition like cancer or a disease that weakens the immune system or has had a severe allergic reaction to a previous vaccine dose.

Is there a link between vaccines and autism?

Some people have suggested that thimerosal (a compound that contains mercury) in vaccines given to infants and young children might have something to do with autism. Others have suggested that the MMR (measles- mumps-rubella) vaccine may be linked to autism. However, numerous scientists and researchers have studied and continue to study the MMR vaccine and thimerosal, and reach the same conclusion: there is no link between MMR vaccine or thimerosal and autism.

Side Effects

What are the side effects of vaccines?

Vaccines, like any medication, may cause some side effects. Most of these side effects are very minor, like soreness where the shot was given, fussiness, or a low-grade fever. These side effects typically only last a couple of days and are treatable. For example, you can apply a cool, wet washcloth on the sore area to ease discomfort.

Serious reactions are very rare. However, if your child experiences any reactions that concern you, call the doctor’s office.

Can vaccines overload my baby’s immune system?

Vaccines do not overload the immune system. Every day, a healthy baby’s immune system successfully fights off thousands of germs. Antigens are parts of germs that cause the body’s immune system to go to work to build antibodies, which fight off diseases.

The antigens in vaccines come from the germs themselves, but the germs are weakened or killed so they cannot cause serious illness. Even if babies receive several vaccinations in one day, vaccines contain only a tiny fraction of the antigens they encounter every day in their environment. Vaccines give your child the antibodies they need to fight off serious vaccine-preventable diseases.

Schedule for Vaccines

Should I get my child shots if she is sick?

Talk with your child’s doctor, but children can usually get vaccinated even if they have a mild illness like a cold, earache, mild fever, or diarrhea. If the doctor says it is okay, your child can still get vaccinated.

Should I delay some vaccines or follow a non-standard schedule?

Children do not receive any known benefits from following schedules that delay vaccines. Infants and young children who follow immunization schedules that spread out or leave out shots are at risk of developing diseases during the time you delay their shots. Some vaccine-preventable diseases remain common in the United States and children may be exposed to these diseases during the time they are not protected by vaccines, placing them at risk for a serious case of the disease that might cause hospitalization or death.

Why can’t I delay some vaccines if I’m planning for my baby to get them all eventually?

Young children have the highest risk of having a serious case of disease that could cause hospitalization or death. Delaying or spreading out vaccine doses leaves your child unprotected during the time when they need vaccine protection the most. For example, diseases such as Hib or pneumococcus almost always occur in the first 2 years of a baby’s life. And some diseases, like Hepatitis B and whooping cough (pertussis), are more serious when babies get them at a younger age. Vaccinating your child according to the CDC’s recommended immunization schedule means you can help protect him at a young age.

Why are there so many doses needed for each vaccine?

Getting every recommended dose of each vaccine provides your child with the best protection possible. Depending on the vaccine, your child will need more than one dose to build high enough immunity to prevent disease or to boost immunity that fades over time. Your child may also receive more than one dose to make sure they are protected if they did not get immunity from a first dose, or to protect them against germs that change over time, like flu. Every dose is important because each protects against infectious diseases that can be especially serious for infants and very young children.

Human Papillomavirus Vaccine (HPV)

Is HPV vaccine safe?

Yes. The safety of HPV vaccine has been well studied. All three HPV vaccines went through years of extensive safety testing before it was licensed by the FDA, which only licenses a vaccine if it is safe, effective, and the benefits outweigh any risks.

After licensure, HPV vaccine safety monitoring by CDC and FDA continues to look for rare or new problems that may happen after vaccination. Since HPV vaccine became available in 2006, there have been many large safety studies conducted in the United States and other countries with reassuring findings. There have been no confirmed safety signals (i.e. higher than expected number of adverse events) observed, with the exception of syncope (fainting).

Fainting and related symptoms (such as jerking movements) can happen after any medical procedure, including vaccination. Some people, especially teens, faint after being vaccinated. To prevent fainting-related injuries, people receiving HPV vaccines should sit or lie down during vaccination, then patients should be observed for 15 minutes after receiving the shot.

Although rare, a severe allergic reaction called anaphylaxis can also occur following HPV vaccines.

CDC continues to monitor the safety of HPV vaccines and provides updates to the Advisory Committee on Immunization Practices (ACIP), as well as the World Health Organization’s Global Advisory Committee for Vaccine Safety (GACVS). 

For additional information and FAQs please visit https://www.cdc.gov/vaccines/parents/FAQs.html and https://www.cdc.gov/vaccinesafety/vaccines/hpv/hpv-safety-faqs.html.