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Original Research

Improving Influenza Vaccination Rates in Pregnancy Through Text Messaging

A Randomized Controlled Trial

Moniz, Michelle H. MD; Hasley, Steve MD; Meyn, Leslie A. MS; Beigi, Richard H. MD, MSc

Author Information
doi: 10.1097/AOG.0b013e31828642b1
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Influenza exposure is common, affecting approximately 11% of pregnant women.1,2 Both pandemic3–8 and seasonal9–11 influenza infections impart disproportionate morbidity to pregnant women with higher rates of serious illness and mortality. Prenatal influenza infection may also be associated with poor pregnancy outcomes, including preterm birth, fetal distress, and cesarean delivery.11

Influenza vaccination is the most effective intervention to mitigate influenza disease during pregnancy.12–14 Both the Centers for Disease Control and Prevention and the American College of Obstetricians and Gynecologists recommend yearly vaccination for all pregnant women regardless of estimated gestational age.1,15 Despite clear advocacy of immunization, vaccine uptake is estimated at only 50% nationally,16–18 a rate well below the Healthy People 2020 target of 80% coverage of pregnant women.19 There is clear need to optimize influenza vaccination of pregnant populations, particularly women unsure about or unwilling to receive the vaccination.

In the past decade, cellular phone text messaging has emerged as a tool available on essentially all mobile phones.20 Advantages of texting include cultural acceptability, rapid and confidential information transmission, and low cost. Texting has been used effectively with some medical illnesses, including diabetes, asthma, hypertension, obesity, bulimia, and substance abuse.21,22 A randomized controlled trial was undertaken to estimate whether text messages encouraging influenza vaccination sent to an ambulatory obstetric population could improve influenza vaccination rates among women unsure about or unwilling to receive the vaccine. We hypothesized that text messaging would enhance vaccine uptake and that patients would be receptive to this means of communication and education.


During two consecutive influenza seasons from September 2010 to February 2012, participants were recruited and enrolled at routine obstetric visits to Magee-Women’s Hospital's outpatient clinic. The trial enrolled women aged 14–50 years who were pregnant at less than 28 weeks of gestation. Participants were required to own a personal cell phone with text messaging capabilities. Women were eligible for participation if they reported not receiving that season's influenza vaccine and if their electronic record lacked documentation of influenza vaccine administration in that season. Women were excluded if they had already received that season's influenza vaccine, if they desired vaccination on the day of potential enrollment, if they had contraindications to vaccination (such as egg allergy or prior adverse reaction to the vaccine), or if they had previously participated in the study. All study participants provided written informed consent in English to trained research staff in a private examination or interview room in the outpatient clinic. The study protocol was approved by the University of Pittsburgh's institutional review board.

Participants were randomized to the two study arms with equal frequency using a permuted block design with random block sizes of two, four, and six. The randomization sequence was generated and group assignments were placed in sequentially numbered, sealed, opaque envelopes by a researcher (L.A.M.) uninvolved in participant recruitment or clinical care. Participants received 12 weekly text messages in one of two text message groups: 1) text messages regarding general preventive health in pregnancy (General); and 2) text messages regarding general preventive health in pregnancy plus the importance of influenza vaccination during pregnancy (Flu).

The general preventive health messages received by all participants covered topics such as the importance of prenatal vitamins, nutritional foods, and seat belt use during pregnancy. The Flu group received additional information in each weekly text message addressing the benefits and safety of influenza vaccination during pregnancy. All text messages were sent through a password-protected online service ( Participants in both groups received usual prenatal care in the outpatient clinic, where prenatal care providers (nurses, midlevel health care providers, physicians) verbally recommend and offer influenza vaccination at each prenatal visit. Health care providers were blind to the groups to which participants were randomized. The flu shot is offered at no cost to clinic patients.

Enrolled participants completed anonymous preintervention and postintervention surveys to assess sociodemographics, preventive health beliefs and behaviors, and attitudes toward text messaging. Preintervention surveys were self-administered and completed on paper at the time of enrollment. Approximately 12 weeks after enrollment (but no later than the 6-week postpartum visit), research staff telephoned participants to complete the exit survey.

As a result of multiple national and local interventions to increase awareness of influenza in the face of the 2009 H1N1 pandemic, we anticipated a clinic vaccination rate of 45%. A sample size of 70 women in each arm would have 80% power to determine whether the vaccination rate increased 55% from the estimated baseline to at least 70% in the intervention arm based on a Fisher’s exact test evaluated at a .050 two-sided significance level. The anticipated difference in group-specific proportions was chosen because of the 300% increase in national vaccination rates of some pregnant populations (from approximately 15% to approximately 45%) observed before and after the 2009 H1N1 influenza pandemic.16,17 Allowing for a 35% attrition rate to account for loss to follow-up, participants requesting no further messages, spontaneous abortions, premature deliveries, and pregnancy complications that might preclude further participation, 216 women were enrolled to ensure 140 women were available at study conclusion for data analysis. The prespecified primary outcome was uptake of the influenza vaccine. Vaccine receipt was verified by review of the clinic's electronic medical record, which automatically documents date of vaccination at the time of vaccine administration. Record review was conducted after exit surveys were completed by a researcher (M.H.M.) unaware of participants' randomization allocation. Secondary end points included demographics, knowledge about and attitudes toward preventive health behaviors during pregnancy (including influenza vaccination), and reported acceptability of text messaging as a means of education and health promotion during pregnancy. These were assessed through participant responses on preintervention and postintervention surveys. Differences in the frequency of influenza vaccine uptake during pregnancy, enrollment characteristics, and self-reported reasons for declining influenza vaccination were assessed using Fisher’s exact test. The Mann-Whitney U test was used to assess differences in the median days to vaccination between the two groups. Statistical analyses were performed using IBM SPSS Statistics 20 software, and all tests evaluated at the two-sided .05 significance level.


Approximately 2,100 obstetric patients received care in the Magee Outpatient Clinic during the study's enrollment periods. Of these, 216 were enrolled in the study (Fig. 1). Eight patients were excluded from the General group and four patients from the Flu group because of enrollment failures. The final intention-to-treat analysis included 204 participants, 100 in the General group and 104 in the Flu group. For the per-protocol analysis, 18 patients in the General group and 28 patients in the Flu group were deemed nonevaluable because they never received text messages, their pregnancy was terminated early (by miscarriage or abortion), or they were lost to follow-up. A total of 158 participants were thus included in the per-protocol analysis (82 in the General group, 76 in the Flu group).

Fig. 1
Fig. 1:
Enrollment and follow-up of participants.Moniz. Text Messaging and Influenza Vaccination. Obstet Gynecol 2013.

A comparison of the two groups at baseline revealed no differences between the groups (Table 1). Greater than half of participants were African American (66%), whereas an additional 27% were white. Educational attainment was low with 90% reporting equivalent to or less than high school education. The majority were unmarried (91%), lived in households with less than $40,000 annual income (88%), and had public or no insurance (88%).

Table 1
Table 1:
Comparison of Baseline Characteristics According to Study Group

The overall influenza vaccination rate among participants was 32% with no difference between participants in the General (31% [n=31]) compared with Flu (33% [n=34]) groups (difference 1.7%, 95% confidence interval [CI] −11.1 to 14.5%; Table 2). Similarly, there were no observed differences in the per-protocol analysis, in which the influenza vaccine uptake was 33% (n=27, General) compared with 37% (n=28, Flu, difference 3.9%, 95% CI −11.0 to 18.8%). Among those participants who did receive the influenza vaccine, timing of vaccination was no different between the two groups (median interval from study enrollment to vaccination was 30 days [range 0–217 days] in General compared with 32.5 days [range 0–119 days] in Flu; P=.45). Vaccinated participants were more likely than nonvaccinated participants to have reported on the baseline survey that influenza vaccination during pregnancy was somewhat or very important (63.1% vaccinated participants compared with 25.9% unvaccinated participants, P<.001); vaccination status of these participants endorsing the importance of the flu vaccine was not affected by treatment arm. Year-to-year variation did not affect the primary outcome (vaccine coverage 35.7% in General compared with 37.9% in Flu, P>.99 in the 2010–2011 season and 29.2% in General compared with 30.7% in Flu, P=.86 in the 2011–2012 season); data from the per-protocol analysis are similarly unaffected by yearly variation. The overall background influenza immunization rate in the outpatient clinic was approximately 25% in the 2010–2011 influenza season and approximately 50% in the 2011–2012 season, producing an average background immunization rate of 37% during the study period.

Table 2
Table 2:
Uptake of Influenza Vaccine According to Study Group

When given multiple choices for the reasons they declined influenza vaccination, participants who were unvaccinated most commonly selected the following: they did not like shots (15%), they were afraid of vaccine side effects (23%), and they had a bad experience with the flu vaccine in the past (15%) (Table 3).

Table 3
Table 3:
Self-Reported Reasons for Declining Influenza Vaccination*

Despite these objections among participants who were not vaccinated, 52% reported that they would get or consider getting the flu shot if it were recommended to them by their prenatal care provider.

The majority of participants in both groups reported that they liked receiving text messages (90%), found them to be helpful (89%), believed that this was a good way for physicians to help patients improve their health (94%), and wanted to continue receiving text messages about how to stay healthy (84%; Table 4). More than 70% of participants felt that receiving text messages about how to stay healthy during pregnancy increased their satisfaction with their prenatal care.

Table 4
Table 4:
Acceptability of Text Messaging


In this investigation, text messages stating the benefits of the influenza vaccine were not effective at increasing influenza vaccination rates during pregnancy among a low-income, urban, ambulatory obstetric population. Overall vaccine uptake was 32% with no significant difference observed in the two study groups. The interval from study enrollment to time of vaccine receipt was also not different between the study groups. Unvaccinated participants' primary reasons for declining influenza immunization were apprehension about vaccine safety and lack of awareness of vaccine need. Despite these concerns, more than half reported that they would get or consider getting the flu shot if it were recommended to them by their prenatal care provider. The text messaging program assessed in this investigation did not translate into higher maternal vaccination rates, suggesting that it was not an effective replacement for direct face-to-face recommendation of influenza vaccination.

These findings differ from those of some other investigators. Text message reminders have been shown to increase rates of hepatitis series completion in adult travelers, receipt of secondary shots in the human papillomavirus vaccine series in adolescents, and influenza vaccination of children.23–25 These studies' findings in adult travelers, adolescents, and children may not be generalizable to obstetric populations. Additionally, prior studies have enrolled individuals with willingness to receive vaccination (in two described studies, participants had already received the first dose of multidose vaccine series). In contrast, the current investigation specifically excluded pregnant women already willing to receive the influenza vaccine, thus potentially selecting for a more vaccine recalcitrant population than other published trials.

The current investigation importantly begins to delineate some of the potential limitations of text messaging as a medium for patient–health care provider communication and patient behavioral change within obstetric populations. These findings come at a time of mounting excitement about mobile technologies for healthcare in the United States. At a national level, the high-profile Text4baby program for pregnant women, with more than 700 supporting partners and more than 250,000 enrollees as of January 2012,26 exemplifies how mobile health technologies are being embraced to improve maternal health. The outcomes of such a widespread intervention among obstetric populations, however, have not been specifically defined. In the current investigation, text messages were well received and positively affected satisfaction with prenatal care but did not increase influenza vaccine uptake. These data highlight the challenges posed by a likely vaccine intractable group and begin to delineate a specific target population in whom texting technology may not suffice to motivate behavioral change.

Conclusions drawn from this investigation are subject to a few limitations. Data were gathered at a single urban, tertiary care facility and results may not be generalizable to patients seen in different settings or with different sociodemographic characteristics. The sociodemographic profile of study participants, however, closely matches that of the overall clinic population, suggesting that selection bias was minimal. The online system used to send text messages allows verification only that messages were sent to patients, not that messages were received. The primary outcome was assessed through review of the clinic's electronic record, which may not uniformly account for patients receiving the vaccine elsewhere. Study outcome may have been affected by flaws in the clinic's overall vaccination process (we cannot verify, for example, that health care providers offered the influenza vaccine to unvaccinated obstetric patients at every prenatal visit). It is also possible that the prestudy estimation of potential benefit was too high. Although this investigation was not powered to detect more modest benefits from a texting intervention, it is unclear whether much smaller differences would be clinically relevant. Lack of observed effect may not have been solely (or even partly) a failure of texting technology itself, but may have reflected an inadequacy in the content or tone of the messages sent. Future investigations should consider assessing more individualized texts appearing to come directly from the patient's health care provider, unequivocally stating the need for vaccination and specifically addressing known patient barriers to vaccination (eg, fear of side effects, unawareness of vaccine need).

Despite these limitations, this article describes a randomized, adequately powered trial of the novel intervention text messaging applied within the context of obstetric care for the important prenatal intervention of influenza vaccination. Although in this investigation text messaging was not able to elicit increased influenza vaccination rates, it highlights the need for ongoing vaccine efforts. Given the known and emerging benefits of influenza vaccination in pregnancy, continuing research is needed to define communication strategies that will improve vaccine uptake among pregnant women unsure about or unwilling to receive influenza vaccination.


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© 2013 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.