Influenza Vaccination in Pregnant Women: A Systematic Review

Table 2

Outcomes and the quality of evidence of influenza vaccination in pregnant women.

Outcome	Population	Study	Followup (weeks)	Measure of association	Result (95% CI)	Quality of evidence
Influenza-like illness	Mothers	Hulka 1964 [34]	12 to 30	RR	0.56 (0.35–0.91)†	High
		Zaman et al. 2008 [38]	24 to 36*	IRR	0.64 (0.43–0.96)†
	Infants	Zaman et al. 2008 [38]	24	IRR	0.71 (0.54–0.93)†	High
Influenza-like illness with fever >38°C	Mothers	Zaman et al. 2008 [38]	24 to 36*	IRR	0.57 (0.30–1.09)†	Moderate^a
	Infants	Zaman et al. 2008 [38]	24	IRR	0.72 (0.49–1.05)†	Moderate^a
Laboratory-confirmed influenza	Infants	Zaman et al. 2008 [38]	24	IRR	0.37 (0.15–0.95)†	Moderate^a
		Eick et al. 2011 [40]	26	RR	0.59 (0.37–0.93)
Acute upper respiratory tract infection	Mothers	Munoz et al. 2005 [36]	1.1 to 26	RR	1.84 (0.87–3.87)†	Very low^a,b
	Infants	Munoz et al. 2005 [36]	5 to 26	RR	1.13 (0.87–1.44)†	Very low^a,b
		France et al. 2006 [37]	≤13	RR	0.83 (0.64–1.08)†
Hospitalization for influenza-like illness	Mothers	Munoz et al. 2005 [36]	6	RR	3.67 (0.23–58.47)†	Very low^a,b
	Infants	Black et al. 2004 [35]	≤17	HR	0.63 (0.30–1.29)	Very low^a,b,c
		Munoz et al. 2005 [36]	1.1 to 26	RR	3.73 (0.23–59.39)†
		France et al. 2006 [37]	≤13	RR	1.39 (0.42–4.58)†
		Eick et al. 2011 [40]	26	RR	0.61 (0.45–0.84)
Medical visit for influenza-like illness	Mothers	Black et al. 2004 [35]	16 or less	HR	1.00 (0.84–1.20)	Moderate^a
		Munoz et al. 2005 [36]†	1.1 to 26	RR	1.35 (1.02–1.78)†
		Zaman et al. 2008 [38]	24 to 36*	IRR	0.75 (0.39–1.44)†
	Infants	Black et al. 2004 [35]	≤17	HR	0.96 (0.89–1.03)	Moderate^a
		France et al. 2006 [37]	≤13	RR	0.96 (0.86–1.07)
		Zaman et al. 2008 [38]	24	IRR	0.58 (0.41–0.82)†
		Eick et al. 2011 [40]	26	RR	0.92 (0.73–1.16)
Prematurity	Infants	Black et al. 2004 [35]	At birth	RR	1.10 (0.97–1.23)†	Very low^a,b
		Munoz et al. 2005 [36]	At birth	OR	0.67 (0.32–1.32)
		Zaman et al. 2008 [38, 39]	At birth	OR	0.48 (0.08–2.74)	Moderate^a
		Omer et al. 2011 [41]‡	At birth	OR	0.60 (0.38–0.94)
		Sheffield et al. 2012 [42]†	At birth	OR	0.86 (0.78–0.95)
Small for gestational age	Infants	Zaman et al. 2008 [38, 39]	At birth	OR	0.44 (0.19–0.99)	Moderate^a
		Omer et al. 2011[41]^‡	At birth	OR	0.74 (0.47–1.15)
		Sheffield et al. 2012 [42]†	At birth	OR	1.00 (0.93–1.07)
Stillbirths	Infants	Sheffield et al. 2012 [42]†	All months	OR	0.61 (0.42–0.88)	Moderate^a
Neonatal death	Infants	Sheffield et al. 2012 [42]†	All months	OR	0.55 (0.35–0.88)	Moderate^a

IRR: incidence rate ratio; RR: relative risk; HR: hazard ratio; OR: odds ratio.
Notes: ∗women were followed during pregnancy, beginning at two weeks after vaccination until delivery and continuing for 24 weeks after delivery. †Data calculated by the authors from information available in the paper. ‡Outcome measured at the peak of the influenza season.
Reasons for rating down the on-the-quality assessment using the GRADE approach.
aSerious imprecision: low number of events.
bThe study design was observational.
cSerious inconsistency: results vary greatly across studies.