Abstract
Background:
Tdap vaccine receipt in the immediate postpartum period has not been well studied.
Objectives:
We study factors associated with Tdap vaccine receipt during both pregnancy and the immediate postpartum period.
Design:
Retrospective study of 2844 pregnant patients that delivered.
Methods:
Factors from demographics, medical history, previous obstetric history, prenatal care, and previous vaccination history were included.
Results:
39.7% of patients received the Tdap vaccine, 39.5% received the Tdap vaccine prior to delivery, and 20.8% received the Tdap vaccine between delivery and discharge. Increased age (relative risk ratio (RRR): 0.98, 95% CI: 0.96, 0.99, p = 0.01) and lower number of prenatal care visits of fewer than 11 (RRR: 0.51, 95% CI: 0.41, 0.64, p < 0.001) were associated with decreased likelihood of vaccine receipt before delivery. Spanish language (before: RRR: 2.35, 95% CI: 1.69, 3.25, p < 0.001; after: RRR: 1.68, 95% CI: 1.13, 2.49, p = 0.01) and South Asian languages (before: RRR: 1.55, 95% CI: 1.03, 2.32, p = 0.04; after: RRR: 1.69, 95% CI: 1.06, 2.69, p = 0.03) had similar patterns for increased likelihood of Tdap vaccine receipt before and after delivery. Race/ethnicity of Hispanic (RRR:1.84, 95% CI: 1.31, 2.59, p = 0.001), Asian (RRR:1.65, 95% CI: 1.22, 2.22, p = 0.001), and receipt of influenza vaccine during current pregnancy (RRR: 1.58, 95% CI: 1.31, 1.91, p < 0.001) were associated with increased likelihood before delivery.
Conclusion:
Prenatal Tdap vaccination is the best way to prevent infection with B. pertussis. Postpartum Tdap vaccination provides some protection for those declining prenatal vaccination. We recommend that clinicians recognize that there are different patterns for Tdap vaccine receipt before and after delivery and tailor Tdap vaccine counseling based on these patterns.
Plain Language Summary
We studied 2,844 consecutive people giving birth at our hospital to see who chose to receive the Tdap vaccine during pregnancy and shortly after delivery. We separately analyzed these two options for vaccination timing. About 40% received no vaccination, 40% were vaccinated before birth, and 20% vaccinated after giving birth but before leaving the hospital. Women who had the recommended 11 prenatal visits or more were more likely to receive vaccination than those with 10 visits or fewer; all patients had attended our prenatal clinic. Those with increased age were less likely to receive the Tdap vaccine before delivery. Those speaking Spanish or South Asian languages were more likely to receive the Tdap vaccine both before and after delivery. Race/ethnicity of Hispanic or Asian, and receipt of the influenza vaccine during the current pregnancy were more likely to receive the Tdap vaccine before delivery. Clinicians should be aware of the different patterns for Tdap vaccine receipt before and after delivery and can tailor their Tdap advice based upon these patterns.
Introduction
Pertussis, or whooping cough, is a serious respiratory disease caused by the bacterium Bordetella pertussis. 1 In 2021, 22.5% of infants under 6 months old who were diagnosed with pertussis in the United States needed to be hospitalized. 2 One review reported that the source of infection was maternal in 39%, and paternal in another 16%. 3
Tdap is a recombinant protein vaccine that protects against tetanus and diphtheria as well as against pertussis. 4 Maternal vaccination against pertussis provides passive immunization of the fetus with maternal IgG as well as protecting the mother directly; vaccination during weeks 27–36 gestation has the greatest impact on reducing pertussis infection in infants. 5 The American College of Obstetrics and Gynecology recommends that pregnant women receive Tdap vaccine at 27–36 weeks of gestation. 6 Mothers who do not receive Tdap during pregnancy should receive the Tdap vaccine immediately postpartum to reduce infant pertussis risk. 6 Prenatal immunization is more effective than postpartum vaccination. The mechanisms of protection differ. 3 Antenatal vaccination creates passive immunity through the transportation of antibodies across the placenta. Immunization both before and after delivery protects the newborn through the “cocoon effect,” surrounding the infant with immunized individuals who will not themselves harbor B. pertussis. However, a pregnant woman who previously received Tdap vaccination as an adolescent, adult, or during a previous pregnancy but was not vaccinated during the current pregnancy should not receive Tdap postpartum. 6 Adoption of these guidelines has increased the proportion of women receiving the Tdap vaccine during pregnancy or shortly after delivery. 7
Studies have elucidated factors associated with Tdap vaccine receipt during pregnancy. Older maternal age is associated with increased odds of Tdap vaccine receipt. 8 Hispanic race/ethnicity is associated with higher odds than non-Hispanic blacks for Tdap vaccine receipt. 9 Blacks had lower odds than whites for Tdap vaccine receipt. 8 Medicaid health insurance is associated with lower odds of Tdap vaccine receipt than private insurance. 10
Physician recommendation, availability of Tdap vaccine onsite, and receipt of influenza vaccine during pregnancy were associated with higher odds for Tdap vaccine receipt. 10 Hypertension history and inadequate prenatal care were associated with lower odds of Tdap vaccine receipt. 9 Parity greater than two was associated with lower odds of Tdap vaccine receipt. 9
We are not aware of any studies that determine factors associated with Tdap vaccine receipt in the immediate postpartum period. This paper reports the association of Tdap vaccine receipt during pregnancy and the first few days after delivery while still in hospital with demographic factors, medical history, previous obstetric history, prenatal care during the current pregnancy, and previous vaccination history.
Methods
Setting
This is a retrospective study of women with live births or stillbirths that were delivered at 28 weeks or later between March 2017 and July 2023. All data were from a public hospital in Brooklyn, New York. Inclusion criteria were 18 years and older and having at least one prenatal care visit at our hospital. Due to statistical concerns of independence, for those who had multiple deliveries, we only included the first delivery.
We classified patients according to their self-identified primary language. Categories included the primary language of either English, Spanish, languages of the European former Soviet Union states (66 Georgian, 477 Russian, 13 Ukrainian), South Asian languages (37 Bengali, 1 Gujarati, 9 Hindi, 1 Punjabi, 123 Urdu), Central Asian languages (2 Tajik, 66 Uzbek), or Other.
Variables
Demographic variables were age (years), self-identified race/ethnicity (White, Black, Hispanic, Asian, other), primary language (see above), and insurance (private, Medicaid/Medicare (public insurance), or self-pay (no insurance coverage)). Medical history variables were asthma, pre-gestational diabetes mellitus, pre-gestational hypertension, lupus, and rheumatoid arthritis. Parity was characterized as one, two, or greater than two. 9 Entry into prenatal care was categorized as first trimester (<14 weeks of gestation), second trimester (14–27 weeks of gestation, and third trimester (>27 weeks). Number of prenatal visits was categorized as (<11 visits or ⩾11 visits). 11 Two measures of vaccination history were used. One was immunity to measles, mumps, or rubella (MMR). The other was the receipt of the influenza vaccine during the current pregnancy. Each variable was measured as no versus yes. The outcome variable was not receiving the Tdap vaccine during the current pregnancy, receiving the Tdap vaccine during the current pregnancy, or receiving the Tdap vaccine between delivery and discharge from the hospital.
Statistical analysis
Mean and standard deviation described the continuous variable of age. Frequency and percentage described the categorical variables. Multivariate multinomial logistic regression was used for the outcome variable of Tdap vaccination. IBM SPSS Statistics Version 29 (IBM Corporation, Armonk, NY, 2022) and Stata SE Version 17 (College Station, TX, 2021) All p-values were two-tailed. The alpha level for significance was p < 0.05.
Results
There were 4652 deliveries after 28 weeks during the study time frame. We excluded 903 deliveries of women who had previously delivered during the study time frame. We also excluded 905 women without prenatal care visits at our hospital. The sample analyzed thus contained 2844 deliveries. None of the women had a history of receiving the Tdap vaccine before their current pregnancy.
Table 1 shows the sample characteristics. For demographics, the mean age was almost 30 years. The largest non-White percentage for race/ethnicity was Hispanic at 27.6%. Slightly fewer than half the sample spoke English as a primary language. More than three-quarters had public health insurance, Medicaid/Medicare. Medical history revealed 15.5% with hypertension and 4.3% with diabetes. There were 86.4% with a parity of one. Almost half began prenatal care in the first trimester. There were 70.1% with fewer than 11 prenatal care visits. For vaccination history, there were 97.2% with MMR immunity, while 37.2% received influenza vaccine during the current pregnancy. Regarding Tdap receipt, 39.7% did not receive the vaccine during the current pregnancy, 39.5% received the vaccine before delivery, and 20.8% received the vaccine post-delivery while still hospitalized.
Descriptive statistics of the sample.
Former European Soviet Union languages: Georgian, Russian, Ukrainian; South Asian languages: Bengali, Gujarati, Hindi, Punjabi, Urdu; Central Asian languages: Tajik, Uzbek.
MMR, measles, mumps, rubella; SD, standard deviation;
Table 2 shows the multivariate multinomial logistic regression analysis. For Tdap vaccine receipt before delivery, the demographic variables of Hispanic race/ethnicity, Asian race/ethnicity, other race/ethnicity, Spanish language, and South Asian languages were each significantly associated with increased likelihood while increased age was associated with decreased likelihood. There were no significant associations for medical history variables. Those with a parity of two were significantly associated with a decreased likelihood of vaccine receipt. A number of prenatal care visits of fewer than 11 was significantly associated with a decreased likelihood of vaccine receipt. Receipt of influenza vaccine during the current pregnancy was significantly associated with increased likelihood. For Tdap vaccine receipt after delivery, Spanish language, South Asian languages, and Central Asian languages were each significantly associated with increased likelihood. Those with parity greater than two were significantly associated with decreased likelihood.
Multinomial multivariate logistic regression analysis for receipt of Tdap vaccine.
Confidence intervals could not be calculated for lupus and rheumatoid arthritis for certain analyses. There were no multicollinearity concerns as indicated by variance inflation factor values <10. The Box-Tidwell test indicated the linearity of the logit of the outcome variable with the continuous predictor variable of age. Pseudo R-square = 0.06.
CI, confidence interval; MMR, measles, mumps, rubella; RRR, relative risk ratio.
Discussion
A striking finding in our study is the large number of people who did not receive the Tdap vaccine prior to delivery but who were vaccinated during postpartum hospitalization. The 60.3% of those vaccinated included 39.5% vaccinated before delivery and 20.8% after delivery. Thus, slightly over a third of vaccinations occurred postpartum. Unfortunately, 39.7% of our sample never received the Tdap vaccine. Clearly, though, failure to receive vaccine during antepartum visits did not represent a firm preference not to be vaccinated. Perhaps the reality of having a newborn baby influences parents to take measures to protect their child’s health. Although Tdap vaccination during pregnancy is the best time for a mother’s antibody response and passive antibody transfer to her future child, postpartum maternal Tdap vaccination offers some protection to a newborn child.12,13 Those caring for pregnant patients should understand that postpartum hospitalization represents a good opportunity to achieve substantially higher vaccination rates.
Previous research reports that antepartum Tdap vaccine receipt during the 2011–2017 interval increased from 1% to 56% for patients with commercial insurance and 0.5%–31.4% for patients with Medicaid insurance. 14 Our findings for total Tdap vaccination receipt are at the high end of previous research findings. We are aware of only one study that reports the percentage of Tdap vaccine receipt after delivery while still in hospital. 8 This study found that depending upon the month, 36%–61% received the Tdap vaccine during pregnancy, while Tdap vaccine receipt immediately after delivery ranged from below 1% to 10%. We observed a much higher percentage of vaccine receipt following delivery. Part of our institutional protocol involves postpartum discussion between physicians and individual unvaccinated patients. This commitment to vaccine education may make a difference. Also, we suggest that cultural patterns in our sample may have influenced Tdap receipt after delivery. Understanding cultural attitudes toward vaccination could inform patient education and lead to higher vaccination uptake during pregnancy.
There was a different pattern for significant predictors for Tdap vaccine receipt before and after delivery. Spanish language and South Asian languages were the only variables significantly associated with an increased likelihood of Tdap vaccine receipt both before and after delivery. For Tdap vaccine receipt before delivery, race/ethnicity of Hispanic, Asian, and others and receipt of influenza vaccine during the current pregnancy were each significantly associated with increased likelihood. Increased maternal age and number of prenatal care visits of fewer than 11 were each significantly associated with decreased likelihood. For Tdap vaccine receipt after delivery, Central Asian languages were significantly associated with increased likelihood. A parity of two was significantly associated with a decreased likelihood of Tdap receipt before delivery, while a parity greater than two was significantly associated with a decreased likelihood of receipt after delivery.
Hispanic race/ethnicity had an increased likelihood of Tdap vaccine receipt during pregnancy but no such association occurred after delivery. Regarding language, patients who spoke Spanish had an increased likelihood of Tdap vaccine receipt both during pregnancy and after delivery. Previous research also shows that Hispanic race/ethnicity was associated with a higher likelihood of Tdap vaccine receipt; however, Spanish interpreter use was not associated with higher Tdap vaccine receipt. 9 These findings are contradictory to those found in our study. Individuals classified as Hispanic race/ethnicity display great cultural heterogeneity. One region with Spanish-speaking Hispanics may have a different pattern from another region with Spanish-speaking Hispanics. Also, many Hispanics in the United States do not use Spanish as their primary language. Consequently, the different pattern for Tdap vaccine receipt for Hispanic race/ethnicity and Spanish speakers is unclear.
The lower number of prenatal care visits was associated with a lower likelihood of Tdap vaccine receipt during pregnancy, but no such association occurred after delivery. However, timing of entry into prenatal care was not associated with a higher or lower rate of Tdap receipt before or after delivery. This is similar to a previous report that a lower number of prenatal care visits was associated with lower Tdap vaccine receipt, but the timing of entry into prenatal care was not associated with a higher or lower rate of Tdap receipt. 7 The number of visits may be more important for acceptance of the Tdap vaccine than the time of the first prenatal visit. More visits allow more opportunities for vaccine education.
Patients who were vaccinated with the influenza vaccine during the current pregnancy were more likely to receive the Tdap vaccine during the current pregnancy. However, MMR immunity was not associated with Tdap receipt. Our finding regarding influenza vaccination is consistent with previous research. 9 We suggest that this association is due to a general positive receptivity for receiving vaccines. MMR immunity is not a good proxy to assess vaccine acceptability because immunity is almost universal. This MMR immunity is due either to widespread vaccination or previous infection.
Increased parity was associated with a lower likelihood of Tdap vaccine receipt. This finding is similar to findings in previous research which showed a higher likelihood of Tdap vaccine receipt with a parity of one but a lower likelihood of Tdap vaccine receipt with a parity greater than two. 9 We speculate that the increasing experience of raising a child after each pregnancy may influence maternal vaccination choices.
In summary, we can consider possible factors that may contribute to whether patients receive vaccination. Global environment, such as the wealth of the society, and whether society members are trustful of government and generally adhere to rules and norms, influences vaccine acceptance. 15 Even in places where people tend to trust and follow general rules and norms, there may be minority groups such as Christian Scientists who for strongly held religious or ideological reasons will decline all vaccination. These factors are beyond institutional control.
Individual preferences, whether cultural or idiosyncratic, are not necessarily stable and are susceptible to change. This is shown by the high vaccine acceptance we observed after delivery in women who were offered, but did not receive, antepartum Tdap. Our findings also suggest that openness to vaccination may be related to language and race/ethnicity—and thus by extension to culture.
Education has the potential to persuade pregnant women to accept Tdap. The higher likelihood for vaccination rates in women who had 11 or more prenatal visits may be due to increased exposure to prenatal education. It also is possible that having a newborn child in the hospital room may emphasize the vulnerability of that child and sway the child’s mother to be vaccinated as a tangible way to protect the new child.
Finally, the commitment of the healthcare system to vaccination is likely to be important. Good education, as compared to pro-forma notification of vaccine availability, may result in improved vaccination rates. If patients give birth at home or in other non-medical settings, vaccines may not be available for early postpartum administration. This is more of an issue for low-income and middle-income nations with fewer resources and more home deliveries.
A strength of our study is that this is the first study to use a multivariate analysis for Tdap vaccine receipt after delivery while still in hospital. There are some study limitations. First, we did not directly measure cultural attitudes. Future research should consider the role of cultural attitudes in influencing Tdap vaccine receipt. Second, we did not measure the level of direct education about Tdap vaccination during prenatal care. Some clinicians may have used pro-forma notification while others may have taken substantial time to discuss the potential benefits of Tdap vaccination. Third, our medical records indicated that no one received the Tdap vaccine before their current pregnancy. It is possible that some women previously received the Tdap vaccine and if they did not receive the Tdap vaccine during their current pregnancy, the recommendation is that they did not need to receive it postpartum. Many of our patients are recent immigrants to the United States. We only had access to medical records at our hospital. Women may not know if they received the Tdap vaccine when they were living outside of the United States.
In conclusion, we demonstrated an ability to achieve a high rate of Tdap vaccine uptake from the antepartum through the immediate postpartum period. Prenatal Tdap vaccination is more effective than postpartum vaccination. The ability to increase vaccine uptake rates after delivery for those declining prenatal vaccination shows that parturients can be receptive to vaccine education even after delivery. Furthermore, protection of the mother from pertussis infection provides indirect protection for her infant, as does vaccination of everyone who frequently comes into content with the infant; this is less effective than prenatal maternal vaccination.
We can infer that attitudes against vaccination often are not stable. This, and differences in vaccine receipt associated with language and racial/ethnic variables, suggests that culturally sensitive education can improve Tdap vaccination rates. Finally, the association between a lower number of prenatal care visits and lower vaccine receipt demonstrates the likely importance of the prenatal care program for obtaining high Tdap vaccination rates.
