In order to assess the safety of breastfed infants after their mother's postpartum immunization with a combined measles-mumps-rubella (MMR) vaccine, the purpose of this study is to investigate whether measles vaccine strain is excreted in breast milk of breastfeeding women with negative rubella and measles serologies.

This is a multicentre prospective study, to evaluate the safety of infant from 50 breastfeeding women, analyzable for primary endpoint, after postpartum immunization with MMR vaccine.

During the screening period, eligibility will be determined based on the inclusion and exclusion criteria. Medical records of pregnant women will be screened by study investigators, who will then propose to the woman to participate to the study during a phone call or a follow-up visit. Screening visit could take place 4 months before delivery planned date up until the day of delivery.

The investigator will explain the study to the woman. A copy of the informed consent documents will be given to the woman for reading and for further information about the study (by email, by post, or personally).

If the woman is willing to participate to the study and after she had given her screening informed consent, a blood sample for measles serological analysis will be drawn.

After signing the consent, women meeting all the inclusion criteria and none of the exclusion criteria will be vaccinated in post partum and before the exit of the maternity at day 0.

Each woman will have a blood draw at day 0 and breast milk samples as well as urine samples at the hospital at day 0 before vaccination.

Each included woman will also provide breast milk and urine home samples at days 7, 11 and 14 after vaccination. Reminder calls will be performed at days 7, 11 and 14 after vaccination.

Women will then be followed and vaccinated 8 weeks after the first vaccination, visit V1.

Each infant will be followed during 8 weeks. An optional blood sample for immunological analysis will be drawn at week 8 (visit v1). Informed consent form signed by the person(s) holding parental authority (both parents or mother only if the father has no parental authority) is needed for the infant to be included as well.

Diary cards will be used to follow the infant and the mother. If Infant and/or mother develop(s) suspected measles symptom(s), they will be evaluated by a study physician as soon as possible, preferably within 24 to 72 hours of acute measles symptom(s) onset.

In case of mother symptoms, infant will be also seen by a physician during mother's supplementary visit.

The visit at day 0 (V0) of the study will be performed at the maternity. The other visits, screening visit, V1 and supplementary visit (SV), will be performed either at the maternity or at the corresponding CIC if applicable. Home samples at 7, 11 and 14 days after vaccination will be directly sent at the laboratory of virology at Limoges. Home sampling can also be performed at the maternity or CIC according to their internal organization.

Inclusion Criteria:

Women:

• Pregnant woman
• Age ≥ 18 years
• Planning to breastfeed her infant (mixed feeding is allowed)
• Having a negative serology for rubella during pregnancy
• Negative serology for measles based on the result from local laboratory
• Affiliated to a social security regimen

Infants:

• Informed consent form signed by the person(s) holding parental authority.
• Term newborn (≥36LMP)

Exclusion Criteria:

Women:

• Woman having a multiple pregnancy

• Woman planning to get pregnant in the month following the 2nd vaccination

• Woman with known or suspected HIV infection

• Woman with known or suspected immunodeficiency

• Woman with family history of hereditary immune deficiency

• Woman not mastering enough the reading / understanding of the French language to be able to consent to participate to the study

• Woman incapable to follow the procedures of the study and to respect study visits for the whole period of the study.

• Woman with contraindication for MMR vaccination:

  • Scarce hereditary problems of fructose intolerance
  • Woman with history of hypersensitivity to the active substances or to any of the excipients of the vaccine
  • Administration of human gammaglobulins in the past 3 to 11 months depending on the dose of human globulins administered (except for Rhophylac®)
  • Acute severe febrile illness within 7 days prior to injection

• Woman under systemic corticosteroids (prednisone, or equivalent ≥10 mg/day) within the previous 15 days or planning to use corticosteroids (i.e. prednisone, or equivalent ≥10 mg/day) during the 15 days following vaccination

• Woman under immunosuppressive therapy within the previous 3 months before vaccination or planning to use immunosuppressive therapy during the 15 days following vaccination Woman participating in any clinical trial with another investigational product 28 days prior to visit V0 or intent to participate in another clinical study with another investigational product at any time during the conduct of this study

• Any other reason which, according to the investigator, may interfere with the evaluation of the study objectives

• Woman with documented history of measles vaccination (1 or 2 doses) and/or history of documented measles

Infants:

• Blood draw is contraindicated or cannot be performed
• Infant with family history of hereditary immune deficiency
• Infant with suspected or confirmed immunodeficiency
• Any other reason which, according to the investigator, may interfere with the evaluation of the study objectives