**3.2. Children: primary vaccination and booster schedule**

The WHO recommends three doses of vaccine in the primary series, the first dose being given at 6 weeks of age (at the latest at 8 weeks of age). The second dose should be given 4–8 weeks after the first one. The last dose should be given at 6 months of age or at any opportunity after. Delaying the third dose may reduce protection against severe illness in the first year of life. A booster dose is recommended after 1 year of age, preferably in the second year of life, 6 months after the primary vaccination scheme. In countries that use aP vaccine, protection diminishes before the age of 6 years old, whereas those who use wP offer a protection that lasts for 6 years or more. A second booster dose should be given from 4 to 6 years of age for both vaccines [16, 43].

National programs currently administering wP vaccination should continue to use wP vaccines for the primary vaccination series. National programs currently using the aP vaccine may continue to use this vaccine but should consider the need for additional booster doses and additional strategies, such as maternal immunization in case of pertussis resurgence. Only the aP vaccine can be administered in individuals from the age of 7 onward. Vaccination at this age must be based on cost-effectiveness mindset, since the priority is always to maintain high vaccination coverage in the first years of life [16].
