Humoral immune response to SARS-CoV-2 in pregnant and nonpregnant women following infection

Abstract

Background: Immune changes that occur during pregnancy may place pregnant women at an increased risk for severe disease following viral infections like SARS-CoV-2. Whether these immunologic changes modify the immune response to SARS-CoV-2 infection during pregnancy is not well understood.

Objective: This study aimed to compare the humoral immune response to SARS-CoV-2 infection in pregnant and nonpregnant women. The immune response following vaccination for SARS-CoV-2 was also explored.

Study design: In this cohort study, 24 serum samples from 20 patients infected with SARS-CoV-2 during pregnancy were matched by number of days after a positive test with 46 samples from 40 nonpregnant women of reproductive age. Samples from 9 patients who were vaccinated during pregnancy were also examined. Immunoglobulin G and immunoglobulin M levels were measured. Trends in the log antibody levels over time and mean antibody levels were assessed using generalized estimating equations.

Results: The median number of days from first positive test to sampling was 6.5 in the pregnant group (range, 3-97) and 6.0 among nonpregnant participants (range, 2-97). No significant differences in demographic or sampling characteristics were noted between the groups. No differences in immunoglobulin G or immunoglobulin M levels over time or mean antibody levels were noted among pregnant and nonpregnant participants following SARS-CoV-2 infection for any of the SARS-CoV-2 antigen targets examined (spike, spike receptor-binding domain, spike N-terminal domain, and nucleocapsid). Participants who were vaccinated during pregnancy had higher immunoglobulin G levels than pregnant patients who tested positive for all SARS-CoV-2 targets except nucleocapsid antibodies (all P<.001) and had lower immunoglobulin M spike (P<.05) and receptor-binding domain (P<.01) antibody levels.

Conclusion: This study suggests that the humoral response following SARS-CoV-2 infection does not seem to differ between pregnant women and their nonpregnant counterparts. These findings should reassure patients and healthcare providers that pregnant patients seem to mount a nondifferential immune response to SARS-CoV-2.

Keywords: COVID-19; antibodies; immunity; immunoglobulin G; immunoglobulin M; pregnancy; vaccination.

Figure 1

Immunoglobulin G levels following SARS-CoV-2 infection by pregnancy status Log IgG levels with 95% confidence bands over time in pregnant (solid line, light gray band) and nonpregnant (dashed line, dark gray band) patients for (A) spike, (B) nucleocapsid, (C) NTD, and (D) RBD proteins. Repeated measures from the same patient coded by color. IgG, immunoglobulin G; NTD, N-terminal domain; RBD, receptor-binding domain.

Figure 2

Immunoglobulin M levels following SARS-CoV-2 infection by pregnancy status Log IgM levels with 95% confidence bands over time in pregnant (solid line, light gray band) and nonpregnant (dashed line, dark gray band) patients for (A) spike, (B) nucleocapsid, (C) NTD, and (D) RBD proteins. Repeated measures from the same patient coded by color. IgM, immunoglobulin M; NTD, N-terminal domain; RBD, receptor-binding domain.

Figure 3

Mean antibody levels following SARS-CoV-2 infection or vaccination by pregnancy status Box plots of log IgG and IgM levels in pregnant positive, nonpregnant positive, and pregnant vaccinated participants; asterisk indicates significant differences in the mean antibody level at P<.05 adjusted for time since infection or vaccination and controlling for repeated measures within the same patient. IgG, immunoglobulin G; IgM, immunoglobulin M.