April 1997
ATLANTA — The availability of the newly licensed combination vaccine against Haemophilus influenzae type b (Hib) and hepatitis B prompted the Advisory Committee on Immunization Practices (ACIP) to draft a statement on the use of this and other combination vaccines.
"We clearly need to delineate an approach for the use of combination vaccines," said ACIP Committee Chairman Jeffrey P. Davis, MD. Davis is chief medical officer, Wisconsin Department of Health and Family Services.
The ACIP draft document refers specifically to the use of Comvax, but a more general statement can be developed regarding the use of other combination vaccines when licensed, Davis said.
The Hib-Hep B combination vaccine (Comvax, Merck & Co.) was licensed by the Food and Drug Administration (FDA) on Oct. 2, 1996. During the October ACIP meeting, a variety of issues were raised. This included whether providers should continue to routinely administer a birth dose of monovalent hepatitis B vaccine and concerns about extra doses of hepatitis B vaccine, said Frank Mahoney, chief of the CDC hepatitis prevention unit, at a recent ACIP meeting here.
The draft document continues to recommend administration of the birth dose of hepatitis B vaccine, but Comvax cannot be used for the birth dose and must not be used in infants younger than 6 weeks of age because of the potential for suppression of the immune response to polyribosylribitol phosphate outer membrane protein complex (PRP-OMPC) with subsequent doses.
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Comvax may be used as one of the acceptable options for providers for hepatitis B and Hib vaccination in infants. Specific recommendations for the use of Comvax are based on knowledge of the HBsAg status of the mother. The ACIP stated three doses of Comvax may be administered to infants whose mothers are HBsAg-negative or HBsAg-positive, regardless of whether a birth dose of hepatitis B was administered.
For infants born to known HBsAg-negative mothers, a three-dose series of Comvax may be administered at 2 months, 4 months and 12-15 months of age, regardless of whether a birth dose of hepatitis B vaccine was administered.
Regarding Hib vaccination, if the series is started late, the number of doses of a PRP-OMPC containing product that should be administered depends on the age of the child when vaccination is begun: three doses if initiated no later than age 11 months; two doses of started at age 12-14 months; and one dose if started at age 15-59 months. A minimum interval of two months between doses of Hib is recommended, although an interval of one month is acceptable.
For infants born to HBsAg-positive mothers, the vaccine may be administered at 2 months, 4 months and 12-15 months to complete postexposure vaccination. These infants should receive monovalent hepatitis B vaccine and HBIG at birth.
In settings where prenatal HBsAg screening is the standard of practice, the ACIP recommends prenatal screening of all pregnant women to monitor which infants require immediate postexposure management to prevent perinatal HBV infection. When the mother's HBsAg status is unknown, or when test results are pending, the infant should receive monovalent hepatitis B vaccine at birth, and the mother should be tested.
If the HBsAg test of the mother is positive, the infant should receive the additional protection of HBIG as soon as possible within seven days. If the test is negative, Comvax may be administered when the infant is 2, 4 and 12-to-15 months old.
In settings where prenatal testing is not routinely conducted, infants should receive monovalent hepatitis B vaccine at birth. Comvax may be given at 2 months, 4 months and 12-15 months to complete the vaccination schedule for both hepatitis B and Hib.
Comvax may also be administered simultaneously with diphtheria-tetanus-pertussis (DTP) and acellular pertussis-containing vaccines (DTaP), oral polio vaccine (OPV) and inactivated polio vaccine (IPV), measles-mumps-rubella (MMR) and varicella vaccines as necessary.
The ACIP also voted against interim coverage of combination vaccines under the Vaccines for Children (VFC) program until they are formally recommended by the ACIP. The committee, however, approved the inclusion of Comvax for use in the VFC program.
The final version of ACIP recommendations on combination Hib-Hep B vaccines is expected later this year.
"It's likely that Comvax will improve three-dose coverage for these infants early in life. We expect it will have a very high efficacy, and mechanisms are in place to monitor the effectiveness," Mahoney said.
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