**1. Introduction**

Pertussis (or whooping cough) is a worldwide endemic-epidemic respiratory infection, caused by *Bordetella pertussis*, a Gram-negative, aerobic, capsulated bacillus.

Since the 1950s, first, the development of whole-cell and subsequently of acellular vaccines, which may be administered in combination with other antigens (e.g., diphtheria and tetanus toxoids), had a huge impact on the incidence of pertussis and on infant mortality, regardless of the type of vaccine and of the immunization schedule used. However, the duration of protection is not long-lasting, but ranges between 4 and 20 years after natural infection and 4 and 12 years after vaccination [1]. This involved, in particular in the presence of high vaccine coverage, a shift

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of infection to older age groups, with often unspecific and unrecognized clinical features. Adult subjects with atypical pertussis, often asymptomatic or paucisymptomatic, can become a source of infection for younger children, especially those younger than 2 months of age, who have not yet started the vaccination programs for infants [2] .

**3. Epidemiology**

age of 5 years [10].

**4. Clinical aspects**

nity, and the use of antibiotic therapy [14].

of deaths of <1 year old infants.

Before the availability of the pertussis vaccine (introduced in the 1950s), about 80% of cases

Pertussis Immunization in Pregnancy: A Review http://dx.doi.org/10.5772/intechopen.72085 65

In 1974, vaccination was included in the "Expanded Programme on immunization" by World Health Organization (WHO), which allowed a gradual increase in vaccine coverage (CV); in 2008, 82% of newborns had received three doses of pertussis vaccine (avoiding 687,000 deaths)

Despite the excellent results related to the worldwide extensive vaccination, WHO data estimated 16 million cases of pertussis in 2010 (95% of which in developing countries), and 195,000 deaths in the pediatric population. In 2013, pertussis caused about 63,000 deaths in children under the

In the USA, the latest CDC estimates reported 15,737 cases in 2016, with a 86% vaccine coverage with three doses. In particular, an incidence rate of 85.5/100,000 and a percentage of hospitalizations of 44% has been registered in children <6 months of age. In children between 6 and 11 months, incidence rate was 27.1/100,000, and 11.9% of them were hospitalized. In the

With the introduction of vaccination programs, pertussis spreading has shifted to older age

Accordingly to WHO data, this shift may be related to several factors, such as the increased recognition of less frequent manifestations of pathology in older adults, the use of more sensitive lab tests, a more accurate surveillance system that covers the entire life span, and the progressive decay of protective immunity related to a reduction in natural boosters [2].

However, the highest rates of morbidity and mortality attributable to pertussis are reported in children <1 year of age, especially in infants younger than 2 months of age [12]. Infants usually start immunization generally not before 2 months of age and this involves a time frame during which the risk of acquiring pertussis infection transmitted by family members and

Clinical presentation is strictly related to the age of acquisition of the infection, the level of immu-

The disease affects all age groups, especially children, and is one of the most important causes

The severity of clinical manifestations is inversely related to the age of affected subjects. In children who have not yet been vaccinated, pertussis has a typical course and can lead to

same year, 7 deaths were registered; 6 of them involved <1 year old subjects [11].

caregivers (mother, older siblings, grandparents, etc.) is very high [13].

occurred in children <5 years and less than 3% of cases in subjects ≥15 years of age [2].

and in 2014, the CV was estimated almost equal to 86% [2, 3].

groups, thus involving adolescents and adults.

A possible solution to limit the likelihood that an infant can be infected during the first months of life is mother's immunization during pregnancy.

Two important results could be achieved through this approach: the first is placental transmission of immunity induced by vaccination; the second is to prevent the mother from being a potential source of infection for the infant.

In the light of the positive experiences of some countries that have recently introduced vaccination in pregnancy, such as USA, Canada, Australia, and UK, vaccination in the third trimester of pregnancy appears to be one of the cornerstones for the prevention of this infection in infants [3].
