Vaccine Effectiveness of monovalent BNT162b2 Vaccine in Pregnant Women
Page last reviewed 11 November 2022
Key Points
Key Points are meant to be a scientific, factual summary of the available information focusing on monovalent Pfizer- BioNTech COVID-19 Vaccine or mRNA COVID-19 vaccines, as supported by referenced publications within this section. Conclusions should not be drawn from the inclusion or absence of information.
- Data on vaccine efficacy in pregnant women has been limited, as this population was excluded from Phase 3 clinical trials. SARS-CoV-2 infection during pregnancy has been associated with increased risk of maternal hospitalization, ICU admission, mechanical ventilation, and other adverse maternal outcomes, such as pre-term delivery and stillbirth.1-4
- Three Real-World Evidence (RWE) studies on vaccine effectiveness (VE) of monovalent BNT162b2 and mRNA vaccination during pregnancy and one study on the impact of maternal vaccination during pregnancy on COVID-19 hospitalization in infants are described in this summary.1-4 The studies cannot be compared due to differences in study design and methodology.
- A retrospective, observational, population-based cohort study in Israel analyzed VE against SARS-CoV-2 infection, hospitalization and death.1 VE results for BNT162b2 are summarized below:
Table Data
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Confirmed infection*
*Confirmed infection= laboratory-confirmed infection with positive SARS-CoV-2 RT-PCR
| Study | Dagan et al, Nat Med1 N= 21,722 |
|---|---|
| Population | Pregnant women, ≥ 16 years |
| Endpoint time period | 7-56 days after 2nd dose |
| Study period | December 2020- June 2021 Alpha (B.1.1.7) predominance |
| Vaccine effectiveness (VE) outcome: | VE% (95% CI) |
| 96 (89- 100) |
Symptomatic infection
| Study | Dagan et al, Nat Med1 N= 21,722 |
|---|---|
| Population | Pregnant women, ≥ 16 years |
| Endpoint time period | 7-56 days after 2nd dose |
| Study period | December 2020- June 2021 Alpha (B.1.1.7) predominance |
| Vaccine effectiveness (VE) outcome: | VE% (95% CI) |
| 97 (91-100) |
Hospitalization
| Study | Dagan et al, Nat Med1 N= 21,722 |
|---|---|
| Population | Pregnant women, ≥ 16 years |
| Endpoint time period | 7-56 days after 2nd dose |
| Study period | December 2020- June 2021 Alpha (B.1.1.7) predominance |
| Vaccine effectiveness (VE) outcome: | VE% (95% CI) |
| 89 (43-100) |
- Another retrospective, observational, population- based study of 15,060 pregnant women in Israel, mean age 31 years, reported a significantly lower risk of RT-PCR confirmed SARS-CoV-2 infection in pregnant women vaccinated with at least 1 dose of BNT162b2. Compared to unvaccinated pregnant women, the vaccine effectiveness for BNT162b2 vaccination against SARS-CoV-2 infection was 78% (95% CI, 57-89) in vaccinated pregnant women, ≥ 28 days after a first dose of vaccine, during a period of Alpha B1.1.7 predominance.2
- A case-control, test- negative design study, based on electronic medical record data from multiple facilities, estimated VE of mRNA vaccines against COVID-19- associated Emergency Department (ED)/ Urgent Care (UC) encounters or hospitalization in pregnant women ages 18-45 years, during a period of Delta (B.1.617.2) and Omicron (B.1.1.529) predominance, compared to unvaccinated non-pregnant women in the US.3
- mRNA vaccination during pregnancy, including with a booster dose, provided protection against ED/UC visits and hospitalization.
- VE estimates were observed to be higher against hospitalization and lower during a period of Omicron predominance.
- Vaccine Effectiveness - VE% (95% CI)- against outcomes of interest, at listed times post last vaccine dose, are summarized below:
Table Data
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ED/UC encounters
(N= 32,842)
| VE% (95% CI) of 2 doses of mRNA vaccine in pregnant women Reference [Unvaccinated] | VE% (95% CI) of 2 doses of mRNA vaccine in non- pregnant women Reference [Unvaccinated] | VE% (95% CI) of 3rd(booster) dose of mRNA vaccine in pregnant women Reference [Unvaccinated] | VE% (95% CI) of 3rd(booster) dose of mRNA vaccine in non- pregnant women Reference [Unvaccinated] | ||||
|---|---|---|---|---|---|---|---|
| Delta | Omicron | Delta | Omicron | Delta | Omicron | Delta | Omicron |
| ≥ 14 days: 83 (68-91) 14-149 days: 84 (69-92) ≥ 150 days: 75 (5- 93) |
≥ 14 days: 16 (–22-42) 14-149 days: 3 (–49-37) ≥ 150 days: 42 (–16-72)** |
≥ 14 days: 83 (82-84) 14-149 days: 88 (87-89) ≥ 150 days: 77 (75-79) |
≥ 14 days: 22 (19-26) 14-149 days: 36 (31-41) ≥ 150 days: 18 (14-22) |
≥ 7 days: 81 (33-95) 7-119 days: 81 (30-95) ≥ 120 days: NC* |
≥ 7 days: 65 (41-79) 7-119 days: 79 (59-89) ≥ 120 days: –124 (–414-2)** |
≥ 7 days: 91 (88-93) 7-119 days: 90 (88-92) ≥ 120 days: 96 (73-99) |
≥ 7 days: 59 (56-62) 7-119 days: 69 (66-72) ≥ 120 days: 16 (7-25) |
Hospitalizations
(N= 2,088)
| VE% (95% CI) of 2 doses of mRNA vaccine in pregnant women Reference [Unvaccinated] | VE% (95% CI) of 2 doses of mRNA vaccine in non- pregnant women Reference [Unvaccinated] | VE% (95% CI) of 3rd(booster) dose of mRNA vaccine in pregnant women Reference [Unvaccinated] | VE% (95% CI) of 3rd(booster) dose of mRNA vaccine in non- pregnant women Reference [Unvaccinated] | ||||
|---|---|---|---|---|---|---|---|
| Delta | Omicron | Delta | Omicron | Delta | Omicron | Delta | Omicron |
| ≥ 14 days: 98 (96-99) 14-149 days: 99 (96-100) ≥ 150 days: 96 (86-99) |
≥ 14 days: 77 (28-93) 14-149 days: 86 (41-97) ≥ 150 days: 64 (–102- 93)** |
≥ 14 days: 93 (91-95) 14-149 days: 95 (93-97) ≥ 150 days: 90 (87-93) |
≥ 14 days: 53 (41-63) 14-149 days: 64 (44-77) ≥ 150 days: 50 (35-61) |
≥ 7 days: 97 (79-100) 7-119 days: 97 (79-100) ≥ 120 days: NC* |
≥ 7 days: 76 (27-92) 7-119 days: 86 (28-97) ≥ 120 days: –53 (–1254-83)** |
≥ 7 days: 99 (96-100) 7-119 days: 99 (95-100) ≥ 120 days: NC* |
≥ 7 days: 68 (54-78) 7-119 days: 73 (60-82) ≥ 120 days: 47 (5-71) |
Footnotes
*NC= not calculated due to sample size being too small; ** The negative and wide confidence intervals observed were due to limited sample size and to lower case counts during periods of Omicron predominance, resulting in more limited power for VE estimation
- A case-control, test- negative design RWE study assessed the effectiveness of maternal mRNA COVID-19 vaccination during pregnancy against hospitalization for COVID-19 among 537 case and 512 control infants younger than 6 months of age, during a period of Delta (B.1.617.2) and Omicron (B.1.1.529) predominance in the US.4
- The overall VE% (95% CI) of maternal vaccination against hospitalization among infants was 52(33-65); 80(60-90) during the Delta period, and 38 (8-58) during the Omicron period.
- VE% (95% CI) was 69 (50-80) when maternal vaccination was given after 20 weeks of pregnancy and 38 (3-60) in the first 20 weeks of pregnancy.
- mRNA COVID-19 vaccination during pregnancy was observed to provide protection against maternal SARS-CoV-2 infection, ED/UC visits, and hospitalizations, in the studies described in this summary.1-3
References: (1) Dagan; (2) Goldshtein; (3) Schrag; (4) Halasa
