A case series exploring the human milk polyclonal IgA1 response to repeated SARS-CoV-2 vaccinations by LC-MS based fab profiling.

"Conflict of interest JBvG is the founder and director of the Dutch National Human Milk Bank and a member of the National Health Council. JBvG has been a member of the National Breastfeeding Council from March 2010 to March 2020. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest."

"The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research received funding through the Netherlands Organization for Scientific Research (NWO) TTW project 15575 (SG and AH), the ENPPS.LIFT.019.001 project (AH) and the Roadmap Program X-omics 184.034.019 (AH). This research received further support by Stichting Steun Emma Kinderziekenhuis. JBvG acknowledges the Amsterdam Infection and Immunity Institute for funding this work through the COVID-19 grant (24175). KD acknowledges the Amsterdam Reproduction and Development Institute for funding this work though the AR&D grant (V.000296)."

"This research project was registered at the Dutch Trial Register on May 1st, 2020, number: NL 8575, https://onderzoekmetmensen.nl/nl/trial/23001."