Advisory Committee on Immunization Practices Update: Report of
PedvaxHIB Lots with Questionable Immunogenicity
Since 1988, the rate of Haemophilus influenzae type b (Hib)
disease
has decreased in the United States primarily because of the
introduction
and use of three Hib conjugate vaccines in infants and children. In
CDC-coordinated active surveillance areas, rates of reported Hib
disease
among children aged less than 5 years have decreased by 95% from
the first
half of 1989 to the first half of 1992 (CDC, unpublished data,
1992). Other
population-based studies with each of the two vaccines licensed for
infants
also have shown decreases in disease incidence in all age groups
(1-3).
One of these vaccines, PedvaxHIB * (Haemophilus b conjugate
vaccine
[Meningococcal Protein Conjugate], MSD, Merck and Co., Inc., West
Point,
Pennsylvania) has been distributed in the United States since 1989
and has
been recommended for use in infants since December 1990. The
manufacturer
is notifying physicians that data obtained after licensure indicate
that
16 lots ** of this vaccine may have lower than expected
immunogenicity. The
lots were initially distributed from August 1990 through August
1991 and
had expiration dates from April 1991 through May 1992. These 16
lots
comprise 366,000 doses of a total of approximately 2 million doses
of
PedvaxHIB distributed, or about 1% of all Hib conjugate vaccine
released
in the United States since January 1990. Although vaccine from
these lots
induced a lower antibody response, the precise level of antibody
necessary
for protection is not known, and there is no clear evidence that
children
receiving vaccine from these lots are at increased risk for
disease. Given
the limited period of distribution of these vaccine lots, it is
unlikely
that many children received all three recommended doses (at 2, 4,
and 12-15
months of age) from lots with reduced immunogenicity. In addition,
most
children who have received vaccine from these lots will now be
greater than
18 months of age and at lower risk for Hib disease. The company
will
contact physicians who received vaccine from these lots and has
suggested
that selected recipients of these lots receive an additional dose
of Hib
conjugate vaccine. Inquiries about use of vaccine from these lots
may be
directed to Merck and Co., Inc. ([215] 652-7300, collect).
All current lots of PedvaxHIB that have been tested have
expected
immunogen- icity. In view of the success of the Hib conjugate
vaccines in
preventing Hib disease, the Advisory Committee on Immunization
Practices
recommends that physicians should ensure all children are
up-to-date with
the recommended Hib conjugate vaccine schedule. To facilitate
postmarketing
evaluation of Hib conjugate vaccines, physicians are encouraged to
record
lot numbers and manufacturers of vaccines administered for all
children,
and to report any case of invasive Hib disease in a child less than
5 years
of age to local and state health departments.
References
Black SB, Shinefield HR, the Kaiser Permanente Pediatric Vaccine
Study
Group. Immunization with oligosaccharide conjugate Haemophilus
influenzae
type b (HbOC) vaccine on a large health maintenance organization
population: extended follow-up and impact on Haemophilus influenzae
disease
epidemiology. Pediatr Infect Dis J 1992;11:610-3.
Santosham M, Wolff M, Reid R, et al. The efficacy in Navajo
infants of
a conjugate vaccine consisting of Haemophilus influenzae type b
polysaccharide and Neisseria meningitidis outer-membrane protein
complex.
N Engl J Med 1991;324:1767-72.
Vadheim CM, Greenberg DP, Eriksen E, et al. Reduction of Hib
disease in
southern California, 1983-1991. In: Program and abstracts of the
32nd
Interscience Conference on Antimicrobial Agents and Chemotherapy.
Washington, DC: American Society for Microbiology, 1992;398.
Use of trade names and commercial sources is for identification
only and
does not imply endorsement by the Public Health Service or the U.S.
Department of Health and Human Services.
** Lot numbers of PedvaxHIB with questionable immunogenicity are
1160S,
1724S, 1726S, 2377S, 2379S, 0485T, 2378S, 2380S, 0405T, 0853T,
0172T,
0173T, 0498T, 0774T, 0884T, and 1288T.
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