Alleviated humoral and cellular immune response in pregnant women upon vaccination against SARS-CoV-2 infection

Objective The maternal immune adaptation to pregnancy ensures fetal development and survival. Concomitantly, this adaptation can interfere with the response to vaccinations. In our present study, we addressed this hypothesis by comparing vaccine-elicited immune responses between pregnant and non-pregnant women.

Material Pregnant (n=31) and non-pregnant women (n=29) were vaccinated with the mRNA-based COVID-19 vaccine Comirnaty following the same vaccination regimen and dosages. Blood was taken from all study participants 2–6 weeks after the second vaccination.

Method Titers of SARS-CoV-2 immunoglobulin (Ig)G antibodies and IgG subclasses were determined using the DiaSorin LIAISON immunoassay and the Milliplex SARS-CoV-2 Antigen Panel respectively. Deep immune phenotyping of isolated peripheral blood mononuclear cells was performed by flow cytometry. Cellular-mediated immunity was assessed by stimulating T cells with the SARS-CoV-2 spike protein (Prot_S; Miltenyi Biotec), IFN-γ release was subsequently measured using a chemiluminescence analyzer.

Results Anti-SARS-CoV-2 IgG antibody levels were significantly lower in pregnant vaccinees compared to non-pregnant vaccinees. Moreover, a distinct reduction in IgG1 was observable. Flow cytometry analysis revealed a reduction of overall T and B cell frequencies in PBMCs of pregnant vaccinees. Additionally, we observed a decreased IFN-γ response upon stimulation of T cells with the spike protein in pregnant vaccinees, compared to non-pregnant vaccinees.

Summary We here identified a blunted response to vaccination in pregnant women compared to non-pregnant women. Our findings highlight that vaccination schemes and dosages used to immunize pregnant women must be carefully revisited. The recommendations for vaccinations during pregnancy should encompass the unique immunological setting mounted during pregnancy.

Publication History

Article published online:
11 October 2022