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3a.16 What are the advantages and disadvantages of the new acellular pertussis vaccine?




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This article is from the Childhood Vaccinations FAQ, by Lynn Gazis-Sax lynng@alsirat.com with numerous contributions by others.

3a.16 What are the advantages and disadvantages of the new acellular pertussis vaccine?

The big advantage is that the acellular vaccine has fewer side
effects. The FDA initially held off on approving it for the earlier
shots (while approving it for the fourth and fifth shots), mainly due
to remaining uncertainty as to whether it is as effective as the whole
cell vaccine. Reports from Japan indicated that it is, but a Swedish
clinical trial indicated efficacy of 59% for one, and 64% for the
other acellular vaccine. However, even this trial did show >90%
efficacy against severe pertussis. (Shapiro) More recent results in
Sweden and Italy indicate it is both safe and effective. On July 31,
1996, the FDA licensed one acellular pertussis vaccine for the inital
three shots, and more followed. The American Association of Pediatrics
has issued guidelines for the use of the new vaccine, which can be
found at their web page, http://www.aap.org.

As of 7/14/95, results were available from two large European studies,
involving 9,829 infants in Sweden and 15,601 infants in Italy. The
National Institute of Allergy and Infectious Disease (in the US)
reported that "three similar experimental vaccines effectively
immunized 84% to 85% of the children in the trials, while resulting in
fewer side effects than current, widely used versions." (Wall Street
Journal, 7/14/95, p. A7A) A surprising result of the studies was that
whole cell pertussis vaccine efficacy rates were lower than usual:
"conventional vaccines provided protection for just 36% of children in
Italy and 48% in Sweden. In the US the conventional vaccine proves
effective in 70% to 95% of the children who are vaccinated." Officials
suggested that infants in these studies might have had a higher
intensity of exposure to the bacteria due to the lack of widespread
vaccination in those countries, and that might explain the lower
efficacy. A fourth acellular vaccine provided protection in 58% of the
cases. The high efficacy and low side effects shown for the acellular
pertussis vaccine in these studies will likely lead to requests that
the FDA also approve the acellular vaccine for the earlier pertusis
shots. More information on recent study results can be found in NEJM,
Vol. 333, Number 16, Oct. 19, 1995 (B. Trollfors and others).

From Mike Dedek:

This next one indicates there's a better vaccine that may soon become
available [Note: this vaccine is now available, and recommended for
all doses in the US and some industrialized countries]:

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In Pediatrics 1992; 89; 882-887, May 1992, "Acellular Pertussis Vaccination
of 2-Month Old Infants in the United States", Pichichero, Francis, et. at.:

ABSTRACT: This is the first study in children from the United States
that evaluates the immunogenicity of and adverse reactions to the
Connaught/Biken two-component acellular pertussis vaccine compared
with whole-cell pertussis vaccine when given as a primary immunization
series at 2, 4, and 6 months of age. Three hundred eighty infants
were studied; 285 received acellular diphtheria-tetanus toxoids-
pertussis (DTP (ADTP)) and 95 received whole-cell DTP (WDTP).
Following the third dose, ADTP vaccination produced higher antibody
responses than WDTP to lymphocytosis-promoting factor (enzyme-linked
immunosorbent assay IgG geometric mean titer (GMT) > 131 vs 9 and
Chinese hamster ovary cell assay GMT > 273 vs 16) and to filamentous
hemagglutinin (IgG GMT > 73 vs 10) (all P < .0001). Agglutinin
responses were higher in WDTP compared with ADTP recipients (GMT > 50
vs 37; P > .02). Local reactions were fewer for all three doses
following ADTP vaccination. Fever, irritability, drowsiness,
anorexia, vomiting, and unusual crying all occurred less frequently in
ADTP compared with WDTP recipients for one or more of the three doses.
We conclude that this two-component ADTP vaccine when given as a
primary series produces greater immunogenicity and fewer adverse
effects than the currently licensed WDTP vaccine.

...A large case-control study in Britain (National Childhood
Encephalopathy Study) estimated that permanent neurologic deficits may
occur after its administration in 1 in 310000 doses of WDTP. However,
a reanalysis of this and similar studies recently has led to the
widely held conclusion that a causal association between WDTP
vaccination and permanent brain damage has not been demonstrated....

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Public Health Rep 1992; 107: 365-366, May 1992/June 1992, "FDA
Approves New Whooping Cough Vaccine"

The Food and Drug Administration (FDA) has licensed a new whooping
cough
vaccine that may cause fewer side effects in children.

The new vaccine is being approved at this time only for the fourth
and
fifth shots. The current vaccine will continue to be used for the
first three shots. Additional research has been undertaken to
ascertain whether it will be effective for preventing pertussis when
used for primary inmunization -- the first three shots -- in infants.

The new vaccine is acellular, meaning that it is made from only
part of the
pertussis organism, as opposed to the whole organism from which the
current vaccine is derived.

Whooping cough ( pertussis) is a highly contagious disease. As
many as 90
percent of nonimmune household contacts acquire the infection. Since
routine immunization against pertussis became common in the United
States, the number of reported cases of disease and deaths from it
has declined from about 120,000 cases with 1,100 deaths in 1950 to an
annual average in recent years of about 3,500 cases with 10
fatalities.

The new vaccine appears to be as effective in older children as the
current
vaccine and to cause fewer adverse reactions. It has been widely
used in Japan
-- where it was developed -- with apparent success in children older
than 2
years. It will be combined with diphtheria and tetanus toxoids (DTP)
and sold under the brand name Acel-Imune.

Gerald Quinnan, MD, acting director of FDA's Center for Biologics,
where the
vaccine was evaluated and licensed, said that the availability of an
acellular vaccine is a significant step forward in infectious disease
control.

The most common adverse reactions seen in clinical trials of the
acellular
pertussis vaccine included tenderness, redness, and swelling at the
injection site, fever, drowsiness, fretfulness, and vomiting.

The new pertussis vaccine component is produced by Takeda Chemical
Industries Ltd. of Osaka, Japan, and is combined with diphtheria and
tetanus toxoids manufactured by Lederle Laboratories of Wayne, NJ.
Lederle will also distribute the product in the United States. The
vaccine is administered by injection.

The approval of the new vaccine comes at a time when the Federal
Government
is emphasizing early childhood immunizations in the wake of the
largest reported measles outbreak in the nation in 20 years -- with
more than 27,600 cases and 89 deaths reported in 1990.

The aim is to reach a goal of full immunization for 90 percent of
children by
the time they are 2 years old.

*************************************************************************

As of September 1999, results are available from still more
studies. Since 1991, seven studies in Europe and Africa evaluated the
efficacy of eight DTaP vaccines given to infants. The vaccines were by
different manufacturers, with varying number and quantity of
antigens. Number of doses varied (three in some, four in others), as
did other aspects of the study design, such as the case definition for
pertussis and the laboratory method used to confirm the diagnosis. For
this reason, the studies can't be compared directly, but within the
individual studies, the efficacy of whole cell vaccine can be compared
with the efficacy of acellular. Acellular was within the range
expected for whole cell. Estimates of efficacy ranged from 59% to
89%. More serious adverse effects (fever over 105 F, persistent crying
for more than three hours, hypotonic hyporesponsive episodes, and
seizures) happened less often with acellular. Really rare adverse
events (encephalopathy and anaphylactic shock) were too rare to show
up in these studies. Acellular pertussis vaccines have also been used
routinely since 1981 in Japan.

Despite the acellular vaccine's comparable efficacy and few adverse
reactions, the whole cell pertussis vaccine retains one advantage
which ensures some continued use. It is cheaper, and more
organizations know how to make it In developing countries, where
pertussis is a major killer, and money for vaccines in short supply,
it is not clear that the advantages of the acellular vaccine justify
the additional cost.

 

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