A study in JAMA Pediatrics reported that better antibody response was found in the human milk from lactating women vaccinated with an mRNA-based vaccine compared with a vector-based vaccine.

The study included a total of 4 vaccines - 2 mRNA-based vaccines (BNT162b2 developed by Pfizer-BioNTech and mRNA-1273 developed by Moderna) and 2 vector-based vaccines (AZD1222 developed by Oxford/AstraZeneca and Ad26.COV2.S developed by Johnson & Johnson/Janssen).

It was observed that detectable IgA antibodies were found in the milk of almost all lactating women who received either the Pfizer-BioNTech (96%) or Moderna (97%) mRNA vaccines, while those who received vector-based vaccines hada comparatively lower level of IgA. Only 39% and 48% showed detectable IgA levels in their milk after being vaccinated with the AstraZeneca and J&J vaccines, respectively.

All participants who received both doses of the Pfizer-BioNTech, Moderna, and AstraZeneca vaccines showed detectable IgG antibody levels, which was observed after 23 days of administration of Pfizer-BioNTech vaccine and 32 days from being vaccinated with Moderna shot, compared to 94 days for AstraZeneca jab. Only 28% of participants who received the single-dose J&J vaccine had detectable IgG levels in their milk.

A limitation of this study was that the neutralizing capacity of the human milk antibodies was not measured.

The study concluded that an mRNA-based vaccine was the optimal choice for lactating women. (MedPage Today, March 14, 2022)