This study has been designed to investigate if:

1. BMI affects the immunogenicity of influenza and pertussis vaccines given during pregnancy.
2. If pertussis vaccine co-administered with influenza vaccine impacts on the immunogenicity of the influenza vaccine.
3. If BMI affects transplacental antibody transfer efficiency following maternal vaccinations.

A clinical observation study to determine whether obesity during pregnancy is associated with altered immunogenicity of influenza and pertussis vaccines during pregnancy. The study will also assess vaccine specific antibody concentrations in cord blood collected from vaccinated women at the time of delivery to estimate any effect of obesity on transplacental transfer of antibodies and will measure and compare cytokine profiles between obese and non-obese participants to determine any correlation with immune responses. This study will enrol 150 pregnant women (50 obese and 100 non-obese) during 2017-2019 to receive a recommended, licensed influenza vaccine (FluQuadri) as well as pertussis vaccination (Adacel) for women enrolled in their third trimester, as part of routine antenatal care. Local and systemic adverse events will be captured using a 7 day diary card and unexpected or serious adverse events will be recorded for the duration of the study. Blood samples will be collected to measure antigen specific vaccine antibody responses. The proportion of influenza vaccine recipients achieving seroprotective antibody titres at 4 weeks post vaccination and persisting at 6 months post vaccination be compared between obese and non-obese recipients.

Inclusion Criteria:

• Participants who, in the opinion of the study staff, can and will comply with the requirements of the protocol (eg. return for follow-up visits, blood collection etc).
• Pregnant women aged 18 years and over at the time of vaccination.
• Able to understand the information sheet and provide a written informed consent.

Exclusion Criteria:

• Any major illness that, in the investigator's judgment, will substantially increase the risk associated with the subject's participation in the study, or interfere with the evaluation of the study objectives.
• History of serious medical conditions (eg cardiac, respiratory, renal, hepatic disorders, diabetes requiring treatment with insulin).
• History of seasonal influenza or dTpa vaccination within the last 6 months prior to enrolment.
• History of any immunosuppressive condition or currently on immunosuppressive medication.
• Any contraindication to influenza or dTpa immunisation.
• Anaphylaxis following a previous dose of any influenza or pertussis containing vaccine.
• History of anaphylaxis to egg.
• Past history of Guillain Barre Syndrome.
• Bleeding diathesis or condition associated with prolonged bleeding that may contraindicate intramuscular injection or blood draw.
• Receipt of immunoglobulins, blood or blood products within the past 6 months.

Pregnant women

A total of 150 healthy pregnant women

Individual participant data (IPD) will not be made available to share with other researchers