Table 1.
Characteristics of included studies
| Authors | Country | Setting | Study design | Dates of recruitment | Participants Inclusion (I)/Exclusion (E) | Intervention Exposure | Comparisons | N | Outcomes |
|---|---|---|---|---|---|---|---|---|---|
| Abu Raya [26] | Israel | Hospital In−/outpatients not specified | PCS | 2013–2014 | I: pregnant women with singleton births at gestational age ≥ 36 weeks E: pregnant women with a newborn <2000 g; immunologic disorder; immunoglobulins in the previous year; immunosuppressive drugs in the current pregnancy; pertussis infection or pertussis-containing vaccine within 5 years or any vaccine besides Tdap within 2 weeks of delivery. | Tdap ≥20 weeks’ gestation | No Tdap during pregnancy | 81 | Anti-pertussis antibodies in mothers’ and infants’ sera measured by ELISA |
| Abu Raya [27] | Israel | Same as above | PCS | 2013–2014 | I: pregnant women with singleton births; gestational age ≥ 36 weeks; intending to breast feedE: same as Abu Raya et al. [26] | Tdap ≥20 weeks’ gestation | No Tdap during pregnancy | 37 | Anti-pertussis antibodies in breast milk measured by ELISA |
| Dabrera [37] | UK | Community- based data | CCS | 2012–2013 | E: any potentially confounding protective effect from active immunisation. | Any pertussis-containing vaccine at any time in pregnancy | No pertussis-containing vaccine during pregnancy | 113 | Pertussis infection in infants; pertussis related complications as measured by the length of hospital stay in infants |
| De Schutter [28] | Belgium | Hospitals In−/outpatients not specified | PCS | 2013–2014 | E: Women who delivered prematurely, who had received another vaccine or any blood product in the previous month. | Tdap during the 2nd or 3rd trimester | No Tdap during pregnancya | 28a | Anti-pertussis antibodies in breast milk measured by ELISA |
| Donegan [32] | UK | Community- based data | RCS | 2012–2013 for vaccine group/ 2010–2012 for control group | I: women aged ≥12 who had a pertussis-containing vaccination during pregnancy and at least 28 days of follow-up data after vaccination | Any pertussis vaccine at any time during pregnancy | No pertussis-containing vaccine during pregnancy | 38,900 | Obstetric and perinatal complications |
| Gall [5] | US | Hospital In−/outpatients not specified | RCS | 2008–2009 | I: pregnant women who had been admitted to the hospital at the study site and their babies | Tdap at any time during pregnancyb | No Tdap during pregnancy | 104 | Anti-pertussis antibodies in infants’ sera measured by ELISA |
| Hardy-Fairbanks [33] | Not specifiedc | Not specifiedb | PCS | 2006 for vaccine group/ 2008–2009 for control group | E: Women with multiple gestations; serious underlying health issues in either the mother or infant, preterm infants, or infants who needed transfusions or who had been advised not to have blood drawn for health reasons | Tdap at any time during pregnancy | No Tdap during pregnancy | 70 | Anti-pertussis antibodies in mothers’ and infants’ sera measured by ELISA |
| Healy [34] | US | Hospital In−/outpatients not specified | RCS | 2009–2011 | I: Women who delivered at ≥37 weeks’ gestation; received Tdap within 2 years; and had plasma–serum pairs available | Tdap at any time during pregnancy | Tdap before pregnancy | 105 | Anti-pertussis antibodies in mothers’ and infants’ sera measured by ELISA |
| Hoang [30] | Vietnam | Community | RCT | 2012–2013 | I: Women aged 18–41 with low risk for complications.E: Women with: any serious underlying medical condition; febrile illness in the 72 h before injection, receipt of TT vaccine in the past month; receipt of Tdap in the past 10 years; receipt of a vaccine, blood product or experimental medicine in the 4 weeks before or after injection; previous severe reaction to any vaccine | Tdap, 20–30 weeks’ gestation | TT during pregnancy | 103 | Anti-pertussis antibodies in mothers’ and infants’ sera measured by ELISA; vaccine-related adverse outcomes; obstetric and perinatal complications. |
| Kharbanda [24] | US | Community- based data | RCS | 2010–2012 | I: Women with singleton pregnancies with a live birth E: women with live virus vaccines during pregnancy; Tdap in the 7 days after the estimated pregnancy start date or in the 7 days before delivery; incomplete birth data | Tdap at any time during pregnancyd | No Tdap during pregnancy | 123,494 | Obstetric and perinatal complications |
| Kharbanda [25] | US | Community- based data | RCS | 2007–2013 | Same as Kharbanda et al. [24] | Tdap at any time during pregnancyd | No Tdap during pregnancy | 163,138 | Obstetric complications occurring within 42 days of vaccination. |
| Ladhani [35] | UK | Community- based data | RCS | 2012–2014 for vaccine group/ 2011–2012 for control group | I: Any infant eligible for the national immunisation program | Tdap-IPV | No pertussis -containing vaccine during pregnancy | 387 | Antibody responses after primary immunisation in infants’ sera measured by ELISA. |
| Maertens [29] | Belgium | Hospitals In−/outpatients not specified | PCS | 2012–2014 | I: Women aged 18–40 with low risk for complications. E: same as Hoang et al. [30] | Tdap at 22–33 weeks’ gestation | No pertussis-containing vaccine during pregnancy | 99 | Anti-pertussis antibodies in mothers’ and infants’ sera measured by ELISA; obstetric complications |
| Munoz [31] | US | NIH Vaccine Treatment Evaluation Unit | RCT | 2008–2012 | I: Women aged 18–45 with no underlying chronic medical conditions, a singleton, uncomplicated pregnancy with normal first- or second-trimester screening test results E: Women who received Tdap or any tetanus-containing vaccine within the prior 2 years | Tdap at 30–32 weeks’ gestation | Placebo | 45 | Anti-pertussis antibodies in mothers’ and infants’ sera measured by ELISA; vaccine-related adverse outcomes; perinatal complications; pertussis infection in infants |
| Shakib [36] | US | Healthcare database | RCS | 2005–2009 | I: Pregnant women 12–45 years of age and their babies E: Women who had documentation of Tdap vaccine within 3 days prior to the delivery outcome | Tdap at any time during pregnancy | No Tdap during pregnancy | 690 | Pertussis infection in infants; perinatal complications |
RCT randomised control trial, PCS prospective cohort study, RCS retrospective cohort study, CCS case-control study, Tdap a combined tetanus toxoid, reduced diphtheria toxoid, acellular pertussis vaccine, TdaP/IPV a combined tetanus, low-dose diphtheria, five-component acellular pertussis, inactivated polio vaccine, TT tetanus toxoid vaccine, ELISA Enzyme-linked immunosorbent assays
aDe Schutter et al. compared different maternal pertussis vaccination strategies. This review only included women with Tdap during pregnancy (n = 19) and women with no pertussis vaccination for at least for 5 years before delivery (n = 9)
bWomen in the study were encouraged to receive Tdap during the second trimester of pregnancy, but the exact timing of its administration could not be determined
cHardy-Fairbanks et al. did not mention the study setting. The study appears, however, to have been conducted in the United States, according to the available information (the authors’ institutional affiliations and the acknowledgements section). The authors also described cases of pertussis that had been reported in New Hampshire during the period when the study participants were recruited
dTdap vaccine received from 8 days after the last menstrual period to seven to 8 days before delivery