SARS-CoV-2 mRNA vaccination in lactating mothers: an observational study to assess longer-term immune responses in blood and breast milk, infections and health status after coronavirus (COVID-19) mRNA vaccination in Zurich, Switzerland

SARS-CoV-2 mRNA vaccination in lactating mothers (VLAC): characterization of immune responses in serum and breast milk of lactating women

Status

Active, not recruiting

Phases

Unknown

Study type

Observational

Source

ISRCTN

Registry ID

ISRCTN12344753

Enrollment

Registered

2023-07-28

Start date

2021-11-02

Completion date

Unknown

Last updated

2023-08-07

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

COVID-19 (SARS-CoV-2 infection) Infections and Infestations

Interventions

Individuals receiving any of the mRNA SARS-CoV-2 vaccines approved in Switzerland at the Corona Center of the UZH, who are randomly selected and invited for study participation will be asked to provid

usually day of first vaccine dose), and 3-4 weeks, 6 weeks, 3 months and 6 months after baseline. The questionnaires can be filled before or during the study visits (see below) and will collect the fo

Eligibility

Sex/Gender

Female

Inclusion criteria

Inclusion criteria: 1. Lactating women receiving any of the mRNA SARS-CoV-2 vaccines approved in Switzerland at the Corona Center of the UZH 2. Aged =18 years 3. Able to follow the study procedures 4. Providing informed consent

Exclusion criteria

Exclusion criteria: 1. Non-lactating individuals 2. Having insufficient knowledge of the German language 3. Previously received SARS-CoV-2 vaccine

Design outcomes

Primary

Measure	Time frame
1. Presence of anti-SARS-CoV-2 IgG antibodies in blood and breast milk before receiving the first dose of a vaccine (baseline), at 3-4 weeks and at 6 weeks, tested using the Corona Immunitas serology test from CHUV (Centre Hospitalier Universitaire Vaudois) 2. Presence of anti-SARS-CoV-2 IgA antibodies in blood and breast milk before receiving the first dose of a vaccine (baseline), at 3-4 weeks and at 6 weeks, tested using the Corona Immunitas serology test from CHUV (Centre Hospitalier Universitaire Vaudois)	—

Measure

Time frame

1. Presence of anti-SARS-CoV-2 IgG antibodies in blood and breast milk before receiving the first dose of a vaccine (baseline), at 3-4 weeks and at 6 weeks, tested using the Corona Immunitas serology test from CHUV (Centre Hospitalier Universitaire Vaudois) 2. Presence of anti-SARS-CoV-2 IgA antibodies in blood and breast milk before receiving the first dose of a vaccine (baseline), at 3-4 weeks and at 6 weeks, tested using the Corona Immunitas serology test from CHUV (Centre Hospitalier Universitaire Vaudois)

—

Secondary

Measure	Time frame
1. Proportion of individuals with measurable neutralizing antibodies against the trimeric SARS-CoV-2 spike protein of SARS-CoV-2 variants in serum and breast milk before receiving the first dose of an mRNA SARS-CoV-2 vaccine (baseline), before the second vaccine dose (usually 4 weeks after the first vaccine dose) and 2 weeks after the second vaccine dose (usually 6 weeks after the first vaccine dose), tested using a cell-free neutralization assay based on the competitive inhibition of ACE2 binding to spike protein trimer-bearing beads. 3. Proportion of lactating women and their infants who received a SARS-CoV-2 and experience a SARS-CoV-2 infection after vaccination, assessed with own standardized questionnaires including the information about positive results in SARS-CoV-2 PCR or rapid antigen tests 4. Proportion of lactating women and their infants who experience adverse effects after vaccination of the mother, assessed using own standardized symptom diary handed out at baseline and subsequently collected 6 weeks after baseline. 5. Comparison of differences in antibody level in breast milk according to the age of the mother, age of the baby, duration of lactation, circumstances of birth (e.g., prematurity) and other factors	—

Measure

Time frame

1. Proportion of individuals with measurable neutralizing antibodies against the trimeric SARS-CoV-2 spike protein of SARS-CoV-2 variants in serum and breast milk before receiving the first dose of an mRNA SARS-CoV-2 vaccine (baseline), before the second vaccine dose (usually 4 weeks after the first vaccine dose) and 2 weeks after the second vaccine dose (usually 6 weeks after the first vaccine dose), tested using a cell-free neutralization assay based on the competitive inhibition of ACE2 binding to spike protein trimer-bearing beads. 3. Proportion of lactating women and their infants who received a SARS-CoV-2 and experience a SARS-CoV-2 infection after vaccination, assessed with own standardized questionnaires including the information about positive results in SARS-CoV-2 PCR or rapid antigen tests 4. Proportion of lactating women and their infants who experience adverse effects after vaccination of the mother, assessed using own standardized symptom diary handed out at baseline and subsequently collected 6 weeks after baseline. 5. Comparison of differences in antibody level in breast milk according to the age of the mother, age of the baby, duration of lactation, circumstances of birth (e.g., prematurity) and other factors

—

Countries

Switzerland

Outcome results

None listed

Source: ISRCTN (via WHO ICTRP) · Data processed: Feb 4, 2026