The impact of COVID-19 in pregnancy: Part II. Vaccination to pregnant women

Abstract

Effective strategies are urgently needed to decrease the risk of untoward outcomes of pregnant women with severe acute respiratory syndrome coronavirus 2 (coronavirus disease 2019 [COVID-19]) infection. Pregnant women are a vulnerable population to infectious disease pandemics with dramatically increased infectious diseases-related serious complications, such as the need of hospitalizations, the need of admission to intensive care unit, and the final disease-related death compared with those nonpregnant counterparts or those pregnant women without infection. Several studies have shown that vaccinations in pregnancy are a safe and highly effective strategy, not only for pregnant women but also for fetus and/or newborn because of the passive transplacental transfer of antibodies to the offspring. Active and passive prevention of infectious diseases is approved as effective strategies for women who attempt to become pregnant or during pregnancy. Despite the large and proven scientific evidence, pregnant women still puzzle over whether they should get vaccinated. The question therefore arises: Why are pregnant women so reluctant to receive vaccination? The explanation is more likely in the way that the benefits of vaccination have been communicated “confusedly.” In fact, like virtually all clinical trials, all the COVID-19 vaccine trials have excluded pregnant and lactating women from participating, contributing to uncertainty of safety and efficacy in COVID-19 vaccines that have been well prepared and available for the general adult population worldwide. Moreover, messenger RNA vaccine is a relatively brand-new vaccine, and experience with this type of vaccine is still scarce. It is hard to overcome this innovation deadlock. The knowledge and awareness of pregnant women who are at risk, and full information on the knowledge of vaccines and related preventable diseases in pregnant women may avoid hesitancy and increase vaccine acceptance. The current review is a part two addressing the impact of COVID-19 on pregnant women. We focus on the up-to-date information about the application of vaccination on pregnant women, especially during this COVID-19 pandemic.

Is the Immunization of Pregnant Women against COVID-19 Justified?

“…Blood samples for the immune study were withdrawn 21-26 days after the second vaccine dose and after a median of 12 and 41 days from symptom onset in infected nonpregnant and pregnant women, respectively. The median RBD-IgG binding antibody titers in immunized nonpregnant, pregnant, and lactating women were 37,839, 27,601, and 23,497, respectively, compared to 1321 and 771 in infected pregnant and nonpregnant women, respectively [98]. Similar differences were evidenced when the pseudo-virus neutralizing antibody titers were measured.…”

“…The results of studies published until now show that mRNA COVID-19 vaccines can generate a robust humoral and cell-mediated response in pregnant and lactating women that is quite similar to that observed in nonpregnant women and is significantly superior to that evoked by SARS-CoV-2 infection [19,98,99]. Titers of IgG or IgA antibodies that bind to the SARS-CoV-2 spike receptor binding domain (RBD), serum antibodies that can neutralize viral particles and non-neutralizing antibodies were found to be several times higher in vaccinated women than in SARS-CoV-2-infected patients, regardless of whether they were pregnant, lactating, nonpregnant or nonlactating.…”

“…Moreover, in immunized women, greater CD4 and CD8 T cell responses were evidenced, suggesting the induction of significantly higher immune memory. In the study by Colier et al [98], 103 participants were enrolled. Among them, 30 were pregnant, 16 were lactating, and 57 were neither pregnant nor lactating.…”

“…Similar differences were evidenced when the pseudo-virus neutralizing antibody titers were measured. In vaccinated nonpregnant pregnant and lactating subjects, titers were 901, 910 and 783, respectively, whereas they were 148 and 193 in infected pregnant and nonpregnant women, respectively [98]. Regarding the cellular response, the percentages of spike-specific interferon (IFN)-γ production by CD4 T cells, CD4 central memory T cells, CD8 T cells, and CD8 central memory T cells were comparable in pregnant, lactating, and nonpregnant women.…”

“…The higher immune response of pregnant women to mRNA vaccines than of women with SARS-CoV-2 infection has a significant impact on cord-blood-and breastmilk-specific antibody titers, suggesting efficient transplacental antibody transfer and potential protection of the infant through maternal vaccination and breastfeeding [98][99][100]. In the cord blood of children born to vaccinated women, after the second vaccine dose, the median serum IgG binding antibody titers were at least half of those measured in maternal serum [98][99][100], whereas in breast milk, they were more than 15 times higher than those in infected subjects (25,055 after vaccination and 1593 after natural infection) [98]. A certain degree of protection through breastmilk could be achieved even after the first dose, as specific IgA antibodies could be detected in breastmilk just after the first mRNA vaccine dose [101].…”