**9. Conclusions**

end of the second and the beginning of the third trimester, preferably after the 20th week. If the vaccine has not been given during pregnancy, one dose of dTap should be given immediately after delivery. In 2012, the recommendation was extended to all women at each new pregnancy,

This indication was based on the results of some studies which showed that the production of protective antibodies after vaccination is maximum in the first month and is much lower even after less than 1 year; after 1 year, the antibody protection provided by the mother is no longer sufficient to protect the baby in his first months of life, unless vaccination is made during pregnancy. It has been confirmed that dTap administration should preferably take place during the second trimester of gestation, especially between the 27th and 36th week [49, 50], although a study conducted by Abu Raya et al. has shown that avidity of IgG antibodies against *Bordetella pertussis* is greater if vaccination is performed between the 27th and

Recently, an observational perspective study [53] has been conducted in Switzerland to evaluate the best time for maternal vaccination in order to adequately protect preterm infants who, among newborns, are a group even more susceptible and at risk. Antibody levels, expressed as geometric mean titers, were evaluated in preterm children born from two cohorts of women vaccinated with dTap, one in the second and one in the third trimester. The results showed a significantly higher level of antibodies in infants born from mothers vaccinated in the second compared to those vaccinated in the third trimester. One possible explanation is that immunization during the second trimester allows a longer transfer time and a higher accumulation of antibodies in newborns This is the first study showing the benefits of maternal immunization in the second trimester for preterm infants. Noteworthy, these interesting results have to be validated as it is well known that the placental transfer of antibodies is greatly effective during

There is no evidence of adverse effects on the fetus after maternal vaccination with inactivated or toxoid vaccines, and coadministration of dTap and flu vaccines is allowed, and it is safe in

A study conducted in New Zealand evaluated the safety of dTap vaccine administered during pregnancy; a cohort of 403 newborns was followed for 6–12 months after birth (84% of whom completed a 12-months follow-up), monitoring over time the onset of possible adverse effects related to vaccination. Several parameters such as gestational age at birth, growth parameters, evidence of congenital abnormalities, immunization status, timeliness of immunization, and possible appearance of pertussis infection after birth were considered. The study showed that there were no significant differences in birth weight, gestational age at birth, congenital anomalies or altered growth parameters, comparing newborns from immunized or unvaccinated mothers. No cases of pertussis occurred in the cohort studied, in spite of the high rates of disease in the community and there were no adverse events related to vaccination. Therefore, these data can be added to the growing pool of evidence that dTap vaccine administration during pregnancy is an adequate and safe strategy to reduce the impact of pertussis in infants [56].

In the United States, the CDC recommends a dose of dTap at each pregnancy, between the 27th and 36th week of gestation (preferably between 28th and 32th). dTap vaccine is also recommended

regardless of their previous vaccination status [48].

30th week of gestation [51, 52].

70 Pertussis - Disease, Control and Challenges

the last trimester of pregnancy.

pregnancy and can optimize the immune response [54, 55].

Although the impact of pertussis has been considerably reduced since the introduction of vaccination programs in the 1950s, the disease continues to be a public health issue, especially in children in their first months of life.

The spread of *B. pertussis* in the cohort of infants is facilitated by the circulation of the pathogen among older age groups (where cases are often atypical and misdiagnosed) that easily become sources of infection for unvaccinated children. The shift of the disease to the older age groups is related to waning immunity occurring after both natural infection and immunization.

It is therefore necessary to implement vaccination strategies taking into account the most vulnerable groups. On one hand, it is recommended to administer booster doses with dTpa vaccine every 10 years to maintain effective immune protection in previously vaccinated population. On the other hand, it is necessary to adopt a preventive strategy addressed to younger babies, already starting immunization in the prenatal age. Women's vaccination in the third trimester of pregnancy appears to be an effective tool as it allows, through the transplacental passage of specific antibodies, newborn's protection in the first few months of life, at least until he reaches the right age to start immunization.

For a more complete protection of the infant, it would be desirable to simultaneously promote the cocoon strategy, immunizing all members of the family and those who will be in close contact with the newborn, to avoid the transmission of the bacterium by these subjects.

Given the new epidemiological situation and on the basis of the scientific evidence, vaccination in the third trimester of pregnancy is currently recommended in several countries such as the United States, Canada, Australia and other European countries (UK, Italy, etc.).
