Interventions to increase vaccination against COVID-19, influenza and pertussis during pregnancy: a systematic review and meta-analysis

BACKGROUND: Pregnant women and their babies face significant risks from three vaccine-preventable diseases: COVID-19, influenza, and pertussis. However, despite these vaccines' proven safety and effectiveness, vaccine uptake during pregnancy remains low. METHODS: We conducted a systematic review (PROSPERO CRD42023399488; January 2012 - December 2022 following PRISMA guidelines) of interventions to increase COVID-19/influenza/pertussis vaccination in pregnancy. We searched nine databases, including grey literature. Two independent investigators extracted data; discrepancies were resolved by consensus. Meta-analyses were conducted using random-effects models to estimate pooled effect sizes. Heterogeneity was assessed using the I2 statistics. RESULTS: Out of 2681 articles, we identified 39 relevant studies (n=168,262 participants) across nine countries. Fifteen studies (39%) were randomised controlled trials (RCTs); the remainder were observational cohort, quality-improvement or cross-sectional studies. The quality of 18% (7/39) was strong. Pooled results of interventions to increase influenza vaccine uptake (18 effect estimates from 12 RCTs) showed the interventions were effective but had a small effect (Risk ratio = 1.07, 95%CI 1.03, 1.13). However, pooled results of interventions to increase pertussis vaccine uptake (10 effect estimates from six RCTs) showed no clear benefit (Risk ratio = 0.98, 95%CI 0.94, 1.03). There were no relevant RCTs for COVID-19. Interventions addressed the "three Ps": patient-, provider- and policy-level strategies. At patient level, clear recommendations from healthcare professionals backed by text reminders/written information were strongly associated with increased vaccine uptake, especially tailored face-to-face interventions, which addressed women's concerns, dispelled myths and highlighted the benefits. Provider-level interventions included educating healthcare professionals about vaccines' safety and effectiveness and reminders to offer vaccinations routinely. Policy-level interventions included financial incentives, mandatory vaccination data fields in electronic health records, and ensuring easy availability of vaccinations. CONCLUSIONS: Interventions had a small effect on increasing influenza vaccination. Training healthcare providers to promote vaccinations during pregnancy is crucial, and could be enhanced by utilising mobile health technologies.