Objective Pregnancy is a known risk factor for severe Coronavirus disease 2019. It is important to develop safe vaccines that elicit strong maternal and fetal antibody responses. Methods Registries (ClinicalTrials.gov, the WHO Clinical Trial Registry, and the European Union Clinical Trial Registry) and databases (MEDLINE, ScienceDirect, Cochrane Library, Proquest, Springer, medRxiv, and bioRxiv) were systematically searched in June 20–22, 2021, for research articles pertaining to Covid-19 and pregnancy. Manual searches of bioRxiv and medRxiv were also conducted. Inclusion criteria were studies that focused on Covid-19 vaccination among pregnant women, while review articles and non-human studies were excluded. Infection rate, maternal antibody response, transplacental antibody transfer, and adverse events were described. Results There were 13 observational studies with a total of 48,039 pregnant women who received mRNA vaccines. Of those, three studies investigated infection rate, six studies investigated maternal antibody response, seven studies investigated antibody transfer, three studies reported local adverse events, and five studies reported systemic adverse events. The available data suggested that the mRNA-based vaccines (Pfizer–BioNTech and Moderna) can prevent future SARS-CoV-2 infection. These vaccines did not show clear harm in pregnancy. The most commonly encountered adverse reactions were pain at the injection site, fatigue, and headache, but these were transient. Antibody responses were rapid after the first vaccine dose. After the booster, antibody responses were stronger and associated with better transplacental antibody transfer. Longer intervals between first vaccination dose and delivery were also associated with higher antibody fetal IgG and a better antibody transfer ratio. Conclusions The SARS-CoV-2 mRNA vaccines are encouraged for pregnancy. These vaccines can be a safe option for pregnant women and their fetuses. Two vaccine doses are recommended for more robust maternal and fetal antibody responses. Longer latency is associated with higher fetal antibody responses. Further research about its long-term effect on pregnancy is needed. Systematic review registration PROSPERO (CRD42021261684).

Vaccine effectiveness (VE) and the urgency of booster vaccination against SARS-CoV-2 Omicron variant need evaluation. A systematic search was conducted from 1–6 April, 2022. VE difference (VED) estimates were assessed using random-effects and meta-regression analyses were performed for evaluating VE over time. Compared to full dose, booster dose of overall vaccines provided better protection against any and severe Omicron infections within 3 months (p < 0.001), and within 3 months or more in any, severe, and symptomatic infections (p < 0.001). From meta-regression analysis of overall vaccines, the full-dose VE against any and symptomatic Omicron infections reduced per month by 2.45% and 5.5%, respectively; whereas booster dose effectiveness against any and symptomatic Omicron infections reduced per month by 1.79% and 1.14%, respectively. The VE estimates of booster dose provide excellent protection against symptomatic infection compared to full dose. The VE estimates of Ad26.COV2.S, BNT162b2, ChAdOx1 nCov-19, and mRNA-1273 against Omicron infection are generally moderate, despite the VE estimates declining over time.

The use of remdesivir for pregnant patients with coronavirus disease 2019 (COVID-19) showed conflicting results in prior studies. We aimed to systematically review its efficacy and safety for this population from the existing literature. Methods: On July 26, 2021, registries (ClinicalTrials.gov) and databases (MEDLINE, ScienceDirect, Cochrane Library, JSTOR, DOAJ, and medRxiv) were systematically searched for research articles investigating remdesivir use in pregnant people with COVID-19. Clinical outcome, hospitalization duration, laboratory outcome, mortality, and adverse events were investigated. Results: We obtained 13 observation studies with 113 pregnant people. In these studies, remdesivir improved the clinical condition of pregnant patients with COVID-19, especially those who had a better clinical status at baseline and received earlier remdesivir treatment. Most fetuses were delivered via cesarean section, primarily because of emergency causes. No vertical transmissions were noted. The most reported adverse event was transaminitis, in which 10-day remdesivir treatment yielded more incidence than the 5-day treatment. Conclusions: In pregnancy, the use of Remdesivir in combination with other COVID-19 treatments is inconclusive but its use should be followed with careful monitoring of adverse reactions and transaminase enzyme levels. Further studies are required to confirm its finding.

Objective: Pregnancy is a risk factor for severe Covid-19. Looking for safe vaccines that evoke protective maternal and fetal antibody response is important. Methods: We searched from registries (ClinicalTrials.gov, the WHO Clinical Trial Registry, and the EU Clinical Trial Registry) and databases (MEDLINE, ScienceDirect, Cochrane Library, Proquest, and Springer) up until June 20, 2021. Articles were selected based on inclusion and exclusion criteria after duplicates were removed. Infection rate, maternal antibody response, placental antibody transfer, and adverse events were described. This systematic review was performed with quality assessment and semi-quantitative synthesis according to PRISMA guidelines. Results: Twelve observational studies with a total of 40.509 pregnant women included. The mRNA based vaccines (Pfizer-BioNTech and Moderna) can prevent future SARS-CoV-2 infections (p=0.0004). Both vaccines did not affect pregnancy, delivery, and neonatal outcomes. The most commonly encountered adverse reactions are injection-site pain, fatigue, and headache but only transient. Antibody responses were rapid after the prime dose of vaccines. After booster, antibody responses were higher and associated with better placental antibody transfer. Longer intervals between first vaccination dose and delivery were also associated with higher antibody fetal IgG and better antibody transfer ratio. Conclusions: The Pfizer-BioNTech and Moderna vaccines are efficacious for preventing future SARS-CoV-2 infections. These vaccines can be considered as a safe option for pregnancy and their fetus. Two doses of vaccines were recommended for more robust maternal and fetal antibody responses. Longer latency was associated with higher fetal antibody responses.

Background: There is a need for evaluation regarding vaccine effectiveness (VE) and the urgency of booster vaccination against Covid-19 B.1.1.529 (Omicron) variant. Methods: Systematic search was conducted on April 6th, 2022, on databases (PubMed, ScienceDirect, CENTRAL, Web of Science, Scopus). VE difference (VED) estimates were assessed using random-effects model and DerSimonian-Laird tau estimators. Two models result, i.e., within 3 months and within 3 months or more, are compared. VE versus time meta-regression analysis was evaluated using mixed-effects model with Restricted-Maximum Likelihood tau estimators and Hartung-Knapp adjustments. Results: Ad26.COV2.S, BNT162b2, ChAdOx1 nCov-19, and mRNA-1273 vaccines were included in the analyses. Compared to full dose, booster dose of overall vaccines provided better protection against any (VED=22% (95%CI 15%-29%), p<0.001), severe (VED=20% (95%CI 8%-32%), p=0.001) and symptomatic (VED=22% (95%CI 11%-34%), p<0.001) Omicron infections within 3 months, as well as within 3 months or more (VED=30% (95%CI 24%-37%), p<0.001 for any, VED=18% (95%CI 13%-23%), p<0.001 for severe and VED=37% (95%CI 29%-46%), p<0.001 for symptomatic infections). The meta-regression analysis of overall vaccines revealed that the full dose VE against any and symptomatic Omicron infections were significantly reduced each month by 3.0% (95%CI 0.9%-4.8%, p=0.004) and 5.2% (95%CI 3.3%-7.1%, p=0.006), respectively; whereas booster dose effectiveness against severe and symptomatic Omicron infections were decreased by 3.7% (95%CI 5.1%-12.6%, p=0.030) and 3.9% (95%CI 1.2%-6.5%, p=0.006), respectively. Conclusion: Compared to full dose only, a booster dose addition provides better protection against B.1.1.529 infection. Although the VE estimates of Ad26.COV2.S, BNT162b2, ChAdOx1 nCov-19, and mRNA-1273 vaccines against B.1.1.529 infection after both full and booster doses are generally moderate, and the booster dose provides excellent protection against severe infection, it is important to note that the VE estimates decline over time, suggesting the need for a regular Covid-19 booster injection after certain period of time to maintain VE.