Comvax Side Effects Center

Last updated on RxList: 1/13/2022
Comvax Side Effects Center

What Is Comvax?

Comvax [Haemophilus b Conjugate (Meningococcal Protein Conjugate) and Hepatitis B (Recombinant) Vaccine] is an immunization used to help prevent Haemophilus B (a type of influenza) and Hepatitis B (a viral disease) in children. Comvax vaccine works by exposing your child to a small dose of the bacteria or virus, which causes the body to develop immunity to the disease. Comvax vaccine will not treat an active infection. Comvax is available in generic form.

What Are Side Effects of Comvax?

Common side effects of Comvax include:

  • injection site reactions (pain, redness, swelling, tenderness, a hard lump, or bruising),
  • fever,
  • irritability,
  • fussiness,
  • increased crying,
  • loss of appetite,
  • increased sleeping,
  • vomiting,
  • runny nose,
  • stuffy nose,
  • cold symptoms,
  • cough,
  • joint pain,
  • body aches, and
  • diarrhea

Dosage for Comvax

Comvax is a 3-dose combination series that aligns with routine doctor visits at 2, 4, and 12 to 15 months of age.

What Drugs, Substances, or Supplements Interact with Comvax?

Comvax may interact with steroids, medicines to treat or prevent organ transplant rejection, or medications to treat psoriasis, rheumatoid arthritis, or other autoimmune disorders. Tell your doctor all medications and supplements you use and all vaccines your child recently received.

Comvax During Pregnancy or Breastfeeding

This vaccine is not for use in adults, therefore it is unlikely to be used during pregnancy or while breastfeeding; consult your doctor.

Additional Information

Our Comvax [Haemophilus b Conjugate (Meningococcal Protein Conjugate) and Hepatitis B (Recombinant) Vaccine] Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Digestive Disorders: Common Misconceptions See Slideshow
Comvax Consumer Information

Get emergency medical help if your child has signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Keep track of any and all side effects your child has after receiving this vaccine. When the child receives a booster dose, you will need to tell the doctor if the previous shot caused any side effects.

Call your doctor at once if your child has:

  • high fever (within a few hours or a few days after the vaccine);
  • a seizure; or
  • fussiness, irritability, crying for an hour or longer.

Common side effects may include:

  • irritability, crying;
  • drowsiness;
  • diarrhea, vomiting;
  • rash;
  • pain, swelling, or redness where the shot was given;
  • cold symptoms such as stuffy nose, sneezing, sore throat; or
  • ear infection--fever, ear pain or full feeling, trouble hearing, drainage from the ear, fussiness in a child.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report vaccine side effects to the US Department of Health and Human Services at 1-800-822-7967.

Comvax Professional Information


In clinical trials involving the administration of 7918 doses of COMVAX to 3561 healthy infants 6 weeks to 15 months of age, COMVAX was generally well tolerated. In these studies, infants received COMVAX with licensed pediatric vaccines (n=1745) or investigational vaccines (n=1816). Serious adverse experience data were available for all 3561 infants and non-serious adverse experience data were available for a subset of 1678 infants.

Pivotal Immunogenicity And Safety Study

In the pivotal, randomized, multicenter study, 882 infants were assigned in a 3:1 ratio to receive either COMVAX or PedvaxHIB plus RECOMBIVAX HB at separate injection sites at 2, 4, and 12-15 months of age. Children may have also received routine pediatric immunizations. The children were monitored daily for five days after each injection for injection-site and systemic adverse experiences. During this time, adverse experiences in infants who received COMVAX were generally similar in type and frequency to those observed in infants who received PedvaxHIB plus RECOMBIVAX HB.

The most frequently cited events were mild, transient signs and symptoms of inflammation at the injection site (i.e., pain/soreness, erythema, and swelling/induration), somnolence, and irritability, all of which were prompted for on report cards filled out by parents of vaccinated children. Table 3 summarizes the frequencies of injection-site and systemic adverse experiences within five days of vaccination that were reported among ≥ 1.0% of children in this pivotal trial.

Table 3: Local Reactions and Systemic Complaints Within 5 Days After Injection Reported to Occur in ≥ 1.0%† of Children Given a 3-Dose Course of COMVAX Compared to These Events in Children Given Concomitant Injections of PedvaxHIB and RECOMBIVAX HB

Event Injection 1‡ Injection 2‡ Injection 3
(N=660) %
(N=221) %
Injection Site Reactions
  Pain/Soreness* 34.5 37.6 24.3 25.8 23.9 21.2
  Erythema ( > 1 in.)* 22.4 (2.7) 25.8 (2.7) 25.7 (1.4) 23.5 (3.3) 27.2 (3.0) 24.4 (1.6)
  Swelling/Induration ( > 1 in.)* 27.6 (3.0) 33.5 (4.1) 30.4 (2.9) 31.0 (3.8) 27.2 (3.2) 29.5 (4.1)
Systemic Complaints
  Irritability* 57 46.6 50.7 44.1 32.2 29
  Somnolence* 49.5 47.1 37.4 31.9 21.1 22.3
      unusual, high pitched* 10.6 8.6 6.7 2.3 2.9 3.6
      not otherwise specified 2.3 2.3 1.4 2.3 0.7 1.6
      prolonged ( > 4 hrs.)* 2.4 2.3 0.8 1.4 0.2 0
  Anorexia 3.9 2.3 2 0.9 0.8 0.5
  Vomiting 2.1 1.8 2.5 0.9 1 1.6
  Otitis media 0.5 0 2 1.4 2.7 1.6
  Fever (“F, rectal equiv.)”
    101.0-102.9 14.2 11.9 13.8 12.2 10.5 6.4
     > 103.0 0.8 0 1.6 1.4 2.7 4.3
  Diarrhea 1.7 1.8 0.8 0.9 2.2 0.5
  Upper respiratory infection 0.5 0.5 1.1 0.9 1.3 0.5
  Rash 0.8 0 0.9 0 0.8 0.5
  Rhinorrhea 0.2 0 1.1 0.9 1.3 2.1
  Respiratory congestion 0.6 0.5 1.2 0.9 0.3 0.5
  Cough 0.2 0 0.9 0.5 0.2 1
  Candidiasis, oral 0.3 0.5 0.8 0 0.2 0
  Rash, diaper 0.5 0.5 0.5 0.9 0.2 0
Overall frequency of each event listed above is > 1% even though the frequency after a given dose may be < 1%.
‡Most children received DTP and OPV concomitantly with the first two doses of COMVAX or PedvaxHIB and RECOMBIVAX HB.
*Events prompted for on Vaccination Report Card given to parents/guardians of vaccinees.
** N for injections 1, 2, and 3 equals 655, 639, and 588, respectively, for COMVAX; N for injections 1, 2, and 3 equals 218, 213, and 187, respectively, for PedvaxHIB and RECOMBIVAX HB.
*** Injection site reactions for PedvaxHIB and RECOMBIVAX HB based on occurrence with either of the monovalent components.

Infants Previously Vaccinated with Hepatitis B Vaccine

In a group of infants (N=126) given a three-dose course of COMVAX after previously receiving a dose of Hepatitis B Vaccine (Recombinant) at or shortly after birth, the type, frequency, and severity of adverse experiences did not appear to be greater than those observed in infants in the pivotal study who did not receive hepatitis B vaccine at birth.

Infants 6 Weeks to 15 Months of Age

In clinical trials, 3285 doses of COMVAX were administered to 1678 infants who were monitored for injection-site and systemic adverse experiences from Days 0 to 5 after each injection of vaccine. Of these, 855 infants had safety data following vaccination at approximately 2 months of age, 836 infants at approximately 4 months of age and 1573 infants at 12 to 15 months of age. The most frequently reported adverse experiences ( ≥ 1% of subjects for at least one injection), without regard to causality are listed in decreasing order of frequency within each body system:

Injection Site Reactions: Pain/tenderness/soreness, swelling/induration, erythema; Body as a Whole: Fever; Digestive System: Anorexia, diarrhea, vomiting; Nervous System/Psychiatric: Irritability, somnolence, crying; Respiratory System: Upper respiratory infection, rhinorrhea, cough, rhinitis; Skin: Rash; Special Senses: Otitis media.

Post-Marketing Experience

As with any vaccine, there is the possibility that broad use of COMVAX could reveal adverse experiences not observed in clinical trials. The following additional adverse reactions have been reported with the use of the marketed vaccine.


Anaphylaxis, angioedema, urticaria, erythema multiforme



Nervous System

Seizure, febrile seizures

Potential Adverse Effects

In addition, a variety of adverse effects have been reported with marketed use of either PedvaxHIB or RECOMBIVAX HB in infants and children through 71 months of age. These adverse effects are listed below.




Sterile injection-site abscess; pain at the injection site



Symptoms of hypersensitivity including reports of rash, pruritus, edema, arthralgia, dyspnea, hypotension, and ecchymoses

Cardiovascular System

Tachycardia; syncope

Digestive System

Elevation of liver enzymes


Increased erythrocyte sedimentation rate

Musculoskeletal System


Nervous System

Bell's Palsy; Guillain-Barre Syndrome


Agitation; somnolence; irritability


Stevens-Johnson Syndrome; alopecia

Special Senses

Conjunctivitis; visual disturbances

Adverse Event Reporting

Patients, parents and guardians should be instructed to report any serious adverse reactions to their health-care provider who in turn should report such events to the U.S. Department of Health and Human Services through the Vaccine Adverse Event Reporting System (VAERS), 1-800-822-7967. The health­care provider should inform the parent or guardian of the National Vaccine Injury Compensation Program (NVICP), 1-800-338-2382.

Read the entire FDA prescribing information for Comvax (Haemophilus b Conjugate and Hepatitis B Vaccine)

© Comvax Patient Information is supplied by Cerner Multum, Inc. and Comvax Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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