Pertussis (also known as whooping cough) is a highly contagious, vaccine-preventable respiratory tract disease, caused by the bacteria Bordetella pertussis. It can affect people of all ages, however young unimmunised or partially immunised infants are the most vulnerable group with the highest rates of complications and death. Recent surveillance data and an increase in the number of pertussis outbreaks being reported nationally, indicate an increase in the incidence of pertussis disease in South Africa.To date there is no data on the effect of vaccinating HIV-infected pregnant women with pertussis-containing vaccines, although there is no reason to think that vaccinating these women would be harmful for them or their foetus. The knowledge gaps on the immunogenicity, safety and VE of pertussis vaccination of HIV-infected pregnant women should be addressed. Adacel which is a registered and licensed vaccine manufactured by Sanofi Pasteur, will be tested in this study.

Inclusion Criteria:

• Pregnant women age ≥18 years to <39 years (vaccinated group only).
• Gestational age 20-36 weeks documented by the approximate date of the last menstrual period and corroborated by physical or sonargraphic exam (vaccinated group only).
• Documented to be HIV-infected or HIV-uninfected.
• Good general maternal health.
• Able to understand and comply with planned study procedures.
• Able and willing to provide written informed consent for themselves and infant

Exclusion Criteria:

• Receipt of any live licensed vaccine ≤14 days prior to study initiation.
• Any significant (in the opinion of the site investigator) acute illness.
• Use of anti-cancer systemic chemotherapy or radiation therapy ≤48 weeks of study enrolment or has immunosuppression as a result of an underlying illness or treatment.
• Long term use of glucocorticoids, including oral or parenteral prednisone ≥20 mg/day or equivalent for more than 2 consecutive weeks (or 2 weeks total) ≤12 weeks of study entry, or high-dose inhaled steroids (>800 mcg/day of beclomethasone dipropionate or equivalent) ≤12 weeks before study entry (nasal and topical steroids are allowed).
• Receipt of corticosteroids for preterm labour ≤14 days before study entry.
• Receipt of immunoglobulin or other blood products (with exception of Rho D immune globulin) ≤12 weeks prior to enrolment in this study or is scheduled to receive immunoglobulin or other blood products (with the exception of Rho D immune globulin) during pregnancy or for the first 24 weeks after delivery.
• Receipt of IL2, IFN, GMCSF or other immune mediators ≤12 weeks before enrolment.
• Uncontrolled major psychiatric disorder.
• History of a severe adverse reaction to previous vaccines (vaccinated group only).
• Any condition that would, in the opinion of the site investigator, place the subject at an unacceptable risk of injury or render the subject unable to meet the requirements of the protocol.
• Pregnancy complications (in the current pregnancy) such as pre-term labour, hypertension (BP >140/90 in the presence of proteinuria or BP >150/100, with or without proteinuria or currently on antihypertensive medication) and pre-eclampsia.