The Australian Immunisation Handbook 10th Edition 2013

Pregnancy and breastfeeding below). Data to evaluate the effectiveness of indirect
protection to infants from the cocoon approach are lacking. 28 However, this
approach is expected to reduce infection risk to infants from family members,
known to be an important source of pertussis infection, 13,14 especially for the
youngest infants. 11,12
4.12.4 Vaccines
Pertussis vaccine is available in Australia only in combination with diphtheria,
tetanus and other antigens.
The acronym DTPa, using capital letters, signifies child formulations of
diphtheria, tetanus and acellular pertussis-containing vaccines. The acronym
dTpa is used for formulations that contain substantially lesser amounts
of diphtheria toxoid and pertussis antigens than child (DTPa-containing)
formulations; dTpa vaccines are usually used in adolescents and adults.
Acellular pertussis-containing vaccines have been used for both primary and
booster vaccination of children in Australia since 1999. Whole-cell pertussiscontaining
vaccines were used exclusively before 1997. Between 1997 and 1999
acellular vaccines were used for booster doses. There are a number of acellular
pertussis-containing vaccines that contain three or more purified components
of B. pertussis. In the 3-component vaccines, these components are pertussis
toxin (PT), filamentous haemagglutinin (FHA) and pertactin (PRN). In the
5-component vaccines, fimbrial (FIM) antigens are also included.
Pertussis vaccines provide good protection against severe and typical pertussis,
but substantially less against milder coughing illness. 29,30 Vaccine efficacy of
DTPa vaccines with three or more antigens has been reported as 71 to 78%
for preventing milder symptoms of pertussis and 84% for preventing typical
disease. 30 Epidemiological data suggest that receipt of the 1st dose of the
primary DTPa course significantly reduces the incidence of severe pertussis
disease in young infants, as measured by hospitalisation rates. 31-33 Data on the
duration of immunity following DTPa vaccine indicate that waning occurs 5 to
6 years after the last dose of vaccine. 2,34 However, these studies could not control
for levels of circulating pertussis in the population, which may boost the level
of immunity and lead to over-estimation of the duration of protection against
symptomatic disease. 29,30
Reduced antigen content formulation, dTpa, vaccines are immunogenic. 35-38
A randomised trial in adults reported a point estimate of 92% efficacy against
culture/nucleic acid test-positive disease within 2.5 years of vaccination
with a 3-component monovalent pertussis vaccine. 4 Data on the duration of
immunity to pertussis following a single booster dose of dTpa are limited. Longterm
follow-up of adults vaccinated with dTpa has shown a rapid decline in
levels of pertussis antibodies within the first 2 years after vaccination, with a
continued steady decline out to 10 years after vaccination, although antibody
levels remained above baseline. 39 A similar long-term follow-up of adolescents
304 The Australian Immunisation Handbook 10th edition