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Vaccine Safety
Vaccine Side Effects

At a glance: Vaccines are held to the highest safety standards. Most people who receive vaccines experience no, or only mild, reactions such as fever or soreness at the injection site. Very rarely, people experience more serious side effects, like allergic reactions. 

Like any drug, vaccines are capable of causing serious problems, even death.  However, a decision not to immunize a child also involves risk. It is a decision to put a child at risk for contracting serious, and potentially deadly, diseases. Getting vaccinated is much safer than getting the disease vaccines prevent.

This page answers some common questions about vaccine side effects and describes the mild, moderate, and severe side effects associated with specific vaccines.

Common questions about vaccine side effects:

Vaccine specific side effects:

How many people experience side effects following vaccination?
In most cases, vaccines cause no side effects, or only mild reactions such as fever or soreness at the injection site.  Very rarely, people experience more serious side effects, like allergic reactions.  Severe reactions to vaccines occur so rarely that the risk is usually difficult to calculate.

Do multiple vaccinations increase the risk of side effects? 
Many parents worry when their child needs to receive more than one vaccine at the same time.  Studies show that giving a child multiple vaccinations for different diseases at the same time is safe, effective and does not increase the risk of side effects.  For more information, click here

What signs of a moderate or severe reaction should I look for?
After you or your child are vaccinated, look for any unusual conditions, such as a serious allergic reaction, high fever or behavior changes.  Signs of a serious allergic reaction include difficulty breathing, hoarseness or wheezing, hives, paleness, weakness, a fast heart beat or dizziness, and swelling of the throat.

What should be done if someone has a reaction to a vaccine?

  • Call a doctor. If the person is having a severe reaction take him or her to a doctor right away.
  • After any reaction, tell your doctor what happened, the date and time it happened, and when the vaccination was given. 
  • Ask your doctor, nurse, or health department to file a Vaccine Adverse Event Reporting System (VAERS) form, or call VAERS yourself at 1-800-822-7967.
  • In the rare event that a vaccine injures a child, he or she may be compensated through the National Vaccine Injury Compensation Program (VICP). For more information about VICP visit http://bhpr.hrsa.gov/vicp/ or call 1-800-338-2382.

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Vaccine-specific information

Diphtheria, tetanus, and pertussis vaccines 
(DTaP)

Printable version (vaccine information sheet) (.pdf)

Mild problems (common)

  • Fever (up to about 1 child in 4)
  • Redness or swelling where the shot was given (up to about 1 child in 4)
  • Soreness or tenderness where the shot was given (up to about 1 child in 4)

These problems occur more often after the 4th and 5th doses of the DTaP series than after earlier doses.  Sometimes the 4th or 5th dose of DTaP vaccine is followed by swelling of the entire arm or leg in which the shot was given (up to about 1 child in 30).

Other mild problems include:

  • Fussiness (up to about 1 child in 3)
  • Tiredness or poor appetite (up to about 1 child in 10)
  • Vomiting (up to about 1 child in 50)

These problems generally occur 1-3 days after the shot. 

Moderate problems (uncommon)

  • Seizure (jerking or staring) (about 1 child out of 14,000)
  • Non-stop crying, for 3 hours or more (up to about 1 child out of 1,000)
  • High fever, over 105F (about 1 child out of 16,000)

Severe problems (very rare)

  • Serious allergic reaction (breathing difficulty, shock) (less than 1 out of a million doses)
  • Other severe problems have been reported after DTaP vaccine. These include:
    •    Long-term seizures, coma, or lowered consciousness
    •    Permanent brain damage.

These are so rare it is hard to tell if they are caused by the vaccine.  

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Hepatitis A vaccine (HAV)

Printable version (vaccine information sheet) (.pdf)

Mild problems

  • soreness where the shot was given (about 1 out of  2 adults, and up to 1 out of 5 children)
  • headache (about 1 out of 6 adults and 1 out of 20 children)
  • loss of appetite (about 1 out of 12 children)
  • tiredness (about 1 out of 14 adults)

If these problems occur, they usually come 3-5 days after vaccination and last for 1 or 2 days.

Severe problems

  • serious allergic reaction, within a few minutes to a few hours of the shot (very rare).  

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Hepatitis B vaccine

Printable version (vaccine information sheet) (.pdf)

Mild problems

  • soreness where the shot was given, lasting a day or two (up to 1 out of 11 children and adolescents, and about 1 out of 4 adults)
  • mild to moderate fever (up to 1 out of 14 children and adolescents and 1 out of 100 adults)

Severe problems

  • serious allergic reaction (very rare).

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Pneumococcal conjugate vaccine

In clinical trials (nearly 60,000 doses), pneumococcal conjugate vaccine was associated with only mild reactions:

  • Up to about 1 infant out of 4 had redness, tenderness, or swelling where the shot was given.
  • About 1 out of 3 had a  fever of over 100.4oF, and up to about 1 in 50 had a higher fever (over 102.2oF).
  • Some children also became fussy or drowsy, or had a loss of appetite.

So far, no moderate or severe reactions have been associated with this vaccine.  However, a vaccine, like any medicine, could cause serious problems, such as a severe allergic reaction.  The risk of this vaccine causing serious harm, or death, is extremely small.

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Influenza (Flu) Vaccine

Printable version (vaccine information sheet) (.pdf)

Mild problems:

  • soreness, redness, or swelling where the shot was given
  • fever
  • aches

If these problems occur, they usually begin soon after the shot and last 1-2 days.

Severe problems:

  • Life-threatening allergic reactions are very rare. If they do occur, it is within a few minutes to a few hours after the shot.
  • In 1976, swine flu vaccine was associated with a severe temporary paralytic illness called Guillain-Barré Syndrome (GBS). Influenza vaccines since then have not been clearly linked to GBS, although research suggests a small risk of the syndrome was associated with the influenza vaccines in 1992-1993 and 1993-1994. However, if there is a risk of GBS from current influenza vaccines, it is estimated at 1 or 2 cases per million persons vaccinated . . . much less than the risk of severe influenza, which can be prevented by vaccination.

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Haemophilus influenzae type b (Hib) vaccine

Printable version (Vaccine Information Sheet) (.pdf)

Mild problems

  • Redness, warmth, or swelling were the shot was given (up to 1/4 of children)
  • Fever over 101oF (up to 1 out  of 20 children)

If these problems happen, they usually start within a day of vaccination. They may last 2-3 days. 

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Inactivated polio vaccine (IPV)

Printable version (vaccine information sheet) (.pdf)

Some people who get IPV get a sore spot where the shot was given.  The vaccine used today has never been known to cause any serious problems, and most people don’t have any problems at all with it.

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Lyme disease vaccine

Printable version (vaccine information sheet) (.pdf)
Screen-reader version (vaccine information sheet) (.rtf)

In clinical trials, Lyme disease vaccine has been associated only with mild problems, such as soreness where the shot is given.

Most people who get Lyme disease vaccine do not have any problems with it.

Mild problems

  • soreness where the shot was given (about 1 person out of 4)
  • redness or swelling where the shot was given (less than 1 person out of 50)
  • muscle aches, joint pain, fever, chills (about 1 person out of 15 or less)

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Meningococcal vaccine

Printable version (vaccine information sheet) (.pdf)

Mild problems

  • Some people who get meningococcal vaccine have mild side effects, such as redness or pain where the shot was given. These symptoms usually last for 1-2 days.
  • A small percentage of people who receive the vaccine develop a fever.

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Measles, mumps & rubella (MMR) vaccines

Printable version (vaccine information sheet) (.pdf)

Mild problems

  • Fever (up to 1 person out of 6)
  • Mild rash (about 1 person out of 20)
  • Swelling of glands in the cheeks or neck (rare)

If these problems occur, it is usually within 7-12 days after the shot. They occur less often after the second dose.

Moderate problems

  • Seizure (jerking or staring) caused by fever (about 1 out of 3,000 doses)
  • Temporary pain and stiffness in the joints, mostly in teenage or adult women (up to 1 out of 4)
  • Temporary low platelet count (thrombocytopenia), which can cause a bleeding disorder (about 1 out of 30,000 doses)  
  • Temporary swelling of the lymph nodes (lymphadenopathy) has been reported following receipt of MMR vaccine
  • Temporary inflammation of the parotid gland (a salivary gland near the ear) can also occur.

Severe problems (very rare)

  • Serious allergic reaction (less than 1 out of a million doses)
  • Several other severe problems have been known to occur after a child gets MMR vaccine. But this happens so rarely, experts cannot be sure whether they are caused by the vaccine or not. These include:
    • Deafness
    • Long-term seizures, coma, or lowered consciousness
    • Permanent brain damage 

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Varicella (chickenpox) vaccine

Printable version (vaccine information sheet) (.pdf)

Mild Problems

  • Soreness or swelling where the shot was given  (about 1 out of 5 children and up to 1 out of 3 adolescents and adults)
  • Fever (1 person out of 10, or less)
  • Mild rash, up to a month after vaccination (1 person out of 20, or less). It is possible for these people to infect other members of their household, but this is extremely rare.

Moderate Problems

  • Seizure (jerking or staring) caused by fever (less than 1 person out of 1,000).

Severe Problems

  • Pneumonia (very rare)

Other serious problems, including severe brain reactions and low blood count, have been reported after chickenpox vaccination. These happen so rarely experts cannot tell whether they are caused by the vaccine or not.  If they are, it is extremely rare.

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Anthrax vaccine

Mild Problems

  • Soreness, redness, or itching where the shot was given (about 1 out of 10 men, about 1 out of 6 women)
  • A lump where the shot was given (about 1 person out of 2)
  • Muscle aches or joint aches (about 1 person out of 5)
  • Headaches (about 1 person out of 5)
  • Fatigue (about 1 out of 15 men, about 1 out of 6 women)
  • Chills or fever (about 1 person out of 20)
  • Nausea (about 1 person out of 20).

Moderate Problems

  • Large areas of redness where the shot was given (up to l person out of 20).

Severe Problems

  • Serious allergic reaction (very rare - less than once in 100,000 doses).

As with any vaccine, other severe problems have been reported.  But these events appear to occur no more often among anthrax vaccine recipients than among unvaccinated people.

There is no evidence that anthrax vaccine causes sterility, birth defects, or long-term health problems.

Independent civilian committees have not found anthrax vaccination to be a factor in unexplained illnesses among Gulf War veterans.

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Pneumococcal polysaccharide vaccine (PPV)

Printable version (vaccine information sheet) (.pdf)

PPV is a very safe vaccine.

About half of those who get the vaccine have very mild side effects, such as redness or pain where the shot is given.

Less than 1% develop a fever, muscle aches, or more severe local reactions. 

Severe allergic reactions have been reported very rarely.

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Tetanus and diphtheria vaccine (Td)

Printable version (vaccine information sheet) (.pdf)

Almost all people who get Td have no problems from it.

Mild Problems

  • Soreness, redness, or swelling where the shot was given

Acetaminophen or ibuprofen (non-aspirin) may be used to reduce soreness.

If these problems occur they usually start within hours to a day or two after vaccination.  They may last 1-2 days.

These problems may be worse in adults who get Td vaccine very often.

Severe Problems

These problems happen very rarely:

  • serious allergic reaction
  • deep, aching pain and muscle wasting in upper arm(s). This starts 2 days to 4 weeks after the shot, and may last many months.

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This page last modified on May 11, 2004

   

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