BACKGROUND AND PURPOSE:

• Gray et al. (AJOG, 2021) evaluated the immunogenicity (ability to provoke an immune response) and reactogenicity (ability to provoke expected adverse reactions) of COVID-19 mRNA vaccination in pregnant and lactating women vs non-pregnant controls

METHODS:

• Prospective cohort study
• Participants (≥18 years)
  • Pregnant or nursing
  • Non-pregnant and of reproductive age
• Exposure
  • COVID-19 vaccine (Pfizer or Moderna mRNA vaccine)
• Study design
  • SARS-CoV-2 IgG, IgA and IgM were quantified in sera and breastmilk
  • Timepoints: Baseline | Second vaccine dose | 2 to 6 weeks post second vaccine | Delivery
  • Titers compared to those of pregnant women 4 to 12 weeks following natural infection (ELISA platform used)
  • Neutralizing antibody titers were evaluated for a participant subset who delivered
  • Post-vaccination symptoms were assessed via questionnaire
  • Differences between groups was assessed, including using statistical tools to account for multiple sampling

RESULTS:

• 131 vaccine recipients | Cord blood obtained from 10 deliveries
  • Pregnant: 84
  • Lactating: 31
  • Non-pregnant: 16
• Compared to non-pregnant women, pregnant and lactating women had similar vaccine-induced antibody titers (p=0.24)
  • Pregnant: Median (IQR) 5.59 (4.68 to 5.89]
  • Lactating: Median (IQR) 5.74 (5.06 to 6.22)
  • Non-pregnant: Median (IQR) 5.62 (4.77 to 5.98)
• All vaccine-induced titers were significantly higher than those induced by natural SARS-CoV-2 infection during pregnancy (p<0.0001)
• Vaccine-generated antibodies were present in all umbilical cord blood and breastmilk samples
  • IgG breast milk levels rose concurrently with maternal serum levels
• While neutralizing antibody titers were lower in umbilical cord vs maternal sera, the difference was not statistically significance (p=0.05)
  • Umbilical cord sera: median (IQR) 52.3 (11.7 to 69.6)
  • Maternal sera: 104.7 (61.2 to 188.2)
• Second vaccine dose increased SARS-CoV-2-specific IgG but not IgA, such that IgG was the dominant serum antibody for all groups by 2 weeks post-second vaccine
• Reactogenicity was similar across pregnant, lactating and non-pregnant groups

CONCLUSION:

• Pregnant and lactating women who received either of the COVID-19 mRNA vaccines experienced robust vaccine-induced immunity
  • Immunogenicity and reactogenicity in pregnancy were similar to that seen in non-pregnant women
• The vaccine-induced immunity response was significantly greater than the immune response caused by natural SARS-CoV-2 infection
• Immune transfer to neonates could occur via breastmilk or placenta
• While the authors are clear that this study does not address possible fetal risks, they conclude

While the absolute risk of severe COVID-19 is low in pregnant women, pregnancy is a risk factor for severe disease

These data provide a compelling argument that COVID-19 mRNA vaccines induce similar humoral immunity in pregnant and lactating women as in the non-pregnant population

Learn More – Primary Sources:

COVID-19 vaccine response in pregnant and lactating women: a cohort study

Related ObG Topics:

Covid-19 Vaccines, Pregnancy & Fertility

Guidance on COVID-19 Vaccine Including Pregnancy

Maternal Outcomes and COVID-19: Results from a Large US-Based Cohort

Safety and Efficacy Data of BNT162b2 COVID-19 Vaccine

The Moderna Vaccine: Study Results Presented to ACIP CDC Committee