Pilot Sequential Multiple Assignment Randomized Trial for RSV Vaccine Uptake in Pregnancy

Respiratory syncytial virus (RSV) is the leading cause of hospitalization and death among infants. Each year, up to 80,000 children are hospitalized due to RSV-associated lower respiratory tract infection, with infants having the highest risk. 50% of childhood deaths from RSV are in infants <6 months old. 1 in every 28 deaths among children aged 28 days to 6 months are attributed to RSV. Childhood RSV is also associated with long-term morbidity particularly a 12-fold higher risk of developing asthma. RSV prevention strategies are urgently needed to protect young infants particularly given their vulnerable immunity at birth. Passive immunity via transfer of IgG antibodies from immunized pregnant women offers an evidence-based solution and is endorsed by the American College of Obstetricians and Gynecologists and the Centers for Disease Control. In 2023, the FDA approved the RSVpreF vaccine for use during 32-36 weeks of pregnancy to protect infants from RSV-associated respiratory infection.

Despite the availability of the RSVpreF vaccine and formal guidelines recommending this vaccine in pregnancy during the 2023 RSV season, RSV vaccine uptake among pregnant individuals at our center was astoundingly low. In a review of 676 eligible patients, less than 10% received the RSV vaccine. Similar trends were seen with the COVID-19 and influenza vaccines in pregnancy where pregnant individuals were vaccinated at half of the rate of non-pregnant individuals. General barriers and facilitators for antenatal vaccine uptake have been well studied and are centered on provider recommendation, women's knowledge and beliefs about the safety of the vaccine, and logistical barriers such as on site availability. However, a recent initiative to offer on-site COVID-19 vaccination at a high risk pregnancy clinic resulted in only a 3% uptake of the vaccine among eligible, high-risk obstetric patients, suggesting that vaccine hesitancy, not availability, is a critical driver of the low vaccination rates in this population. Therefore, novel and multiple interventions are needed to address patient motivation and hesitancy, in addition to vaccine availability, to optimize vaccine uptake in pregnancy.

The central hypothesis is that a multimodal approach is needed to enhance RSVpreF vaccine uptake in pregnancy rather than the current standard of care that relies solely on physician recommendations at routine prenatal visits and/or mass messaging to the public. The investigators propose a pilot sequential multiple assignment randomized trial (SMART) to evaluate the effectiveness of a bundle of evidence-based and sequential strategies and test the following aims:

Aim 1: Assess the effectiveness of early (28-30 week) and low-intensity interventions to increase prenatal RSV vaccination uptake The investigators will compare vaccination uptake rates among pregnant patients 28-30 weeks gestation who are randomized to receive one of two low-intensity and universally acceptable interventions: physician counseling at prenatal visits vs routine counseling + patient visual aid administration (Figure 1). The investigators hypothesize that the combination of a visual aid with routine counseling will increase vaccination uptake rates by 34 weeks gestation. The investigators will explore whether demographic, clinical, or psychosocial factors modify the effects of each intervention.

Aim 2: Assess the effectiveness of late (34-36 week) higher-intensity interventions to increase prenatal RSV vaccination uptake for those who remain unvaccinated at 34 weeks gestation. The investigators will compare vaccination uptake rates in patients who remain unvaccinated at 34 weeks between two higher-intensity interventions: targeted patient phone calls encouraging vaccination versus individual physician reminders on the day of patient appointment. The investigators hypothesize that targeted patient calls will result in the highest vaccination uptake rates due to prior literature supporting the efficacy of this intervention. The investigators will explore whether demographic, clinical, or psychosocial factors modify the effects of each intervention.