By Rebecca H. Allen, MD, MPH

Associate Professor, Department of Obstetrics and Gynecology, Warren Alpert Medical School of Brown University, Women and Infants Hospital, Providence, RI

Dr. Allen reports she receives grant/research support from Bayer and is a consultant for Merck.

SYNOPSIS: In this cross-sectional analysis, pregnant women disproportionately accounted for 24-34% of influenza-associated hospitalizations among women aged 15 to 44 years, and infants younger than 2 months of age comprised the highest proportion of pertussis deaths. The reasons why pregnant women did not elect recommended immunizations included not believing they were effective, not knowing they should receive Tdap every pregnancy, and being concerned that the vaccines would harm the fetus.

SOURCE: Lindley MC, Kahn KE, Bardenheier BH, et al. Vital signs: Burden and prevention of influenza and pertussis among pregnant women and infants — United States. MMWR Morb Mortal Wkly Rep 2019;68:885–892.

This cross-sectional study was conducted by the Centers for Disease Control and Prevention (CDC) to estimate influenza and Tdap vaccination rates among pregnant women. This researchers also evaluated influenza hospitalization among pregnant women and infant hospitalization and death associated with influenza and pertussis. To ascertain vaccination rates, an internet survey was conducted March 27-April 8, 2019, among U.S. adult women ages 18-49 years who reported being pregnant any time since Aug. 1, 2018. A total of 2,626 women completed the survey, and the data were weighted to reflect age, race/ethnicity, and geographic distribution of the U.S. population of pregnant women. Participants’ pregnancy and vaccination status was self-reported and not verified via medical record review. To assess hospitalization rates, data from national surveillance systems (Influenza Hospitalization Surveillance Network and the Influenza-Associated Pediatric Mortality Surveillance System) for the 2010-2011 through 2017-2018 influenza seasons were queried to quantify the proportion of influenza-associated hospitalizations among pregnant women ages 15-44 years and the number of influenza-associated hospitalizations and deaths among infants younger than 6 months of age. From 2010-2017, pertussis case counts, hospitalizations, and mortality in infants younger than 2 months of age also were obtained from the National Notifiable Diseases Surveillance System.

During the 2010-2011 through 2017-2018 influenza seasons, 2,341 influenza-associated hospitalizations among pregnant women were reported. Pregnant women accounted for 24-34% of the hospitalizations among women ages 15 to 44 years. During the same period, among infants younger than 6 months of age, there were 100 laboratory-confirmed influenza-associated deaths, with an average rate of influenza-associated hospitalizations of 133 per 100,000. From 2010-2017, there were 3,928 pertussis hospitalizations among infants younger than 2 months of age, with 77 deaths, accounting for 69% of pertussis deaths among infants younger than 12 months of age.

In the internet survey conducted as part of this study, 53.7% of eligible respondents reported influenza vaccination before or during pregnancy, and 54.9% reported Tdap vaccination during pregnancy. Only 35% of participants reported receiving both vaccines. Compared to the referent group, vaccination coverage for both influenza and Tdap was lower among non-Hispanic black women, and women who had less than a college education, were unmarried, lived below the poverty line, lived in the South, were publicly insured, and did not report a vaccination offer or referral from a healthcare provider. Healthcare provider offer or referral for vaccination was reported by 73.3% of respondents for influenza vaccine and 76.0% of respondents for Tdap. Among those who received an offer or referral, 65.7% received the influenza vaccine and 70.5% received the Tdap. Participants most commonly reported opting not to receive the influenza vaccine because they believed it was ineffective (17.6%). For Tdap, the most commonly reported reason for not getting vaccinated was not realizing that it was needed during each pregnancy (37.9%). For both vaccines, the second most common reason for electing not to receive the vaccine was concern about safety risks to their infant (influenza = 15.9%; Tdap = 17.1%).

COMMENTARY

This timely report by the CDC emphasizes that we all can do more to encourage pregnant women to receive influenza and pertussis vaccines. While pregnant women make up only 9% of the population of women ages 15 to 44 years, they accounted for 24-34% of influenza hospitalizations during the eight years of surveillance. Infants younger than 2 months of age cannot receive the Tdap vaccine themselves and infants younger than 6 months of age cannot receive the influenza vaccine. Therefore, their protection against these diseases relies on antibodies passed through the placenta during pregnancy from their mother’s immunization.1,2 It is estimated that influenza vaccination during pregnancy lowers the risk of influenza hospitalization in pregnant women by an average of 40% and by 72% in infants younger than 6 months of age.3 Similarly, Tdap vaccination during pregnancy lowers the risk of whooping cough in infants younger than 2 months of age by 78% and hospitalization due to whooping cough by 91%.

While there are limitations to self-reported data, this study found that vaccination rates were higher among women who reported being offered or referred for vaccination. However, one-third of women whose providers did offer or refer them for vaccination remained unvaccinated. Unfortunately, the study also showed that immunization rates were lower among women of lower socioeconomic status. We need to do a better job of combating myths that influenza and Tdap vaccines are unsafe or do not work and try to engender trust in the healthcare system. Additionally, OB/GYNs should try to stock recommended vaccines in their offices, since studies show that immunization rates are higher when a healthcare provider can offer and administer a vaccine during the same visit.4

The CDC and the American College of Obstetricians and Gynecologists further recommend that healthcare providers:1-3

  • Discuss the benefits and safety of vaccination with pregnant women early and often.
  • Strongly recommend influenza and Tdap vaccines to pregnant women.
  • Offer influenza and Tdap vaccines to pregnant women or provide referrals to other vaccination providers.
  • Reinforce that maternal vaccination is the best way to protect babies from influenza and whooping cough.

REFERENCES

  1. [No authors listed]. ACOG Committee Opinion No. 732: Influenza vaccination during pregnancy. Obstet Gynecol 2018;131:e109-e114.
  2. Committee on Obstetric Practice, Immunization and Emerging Infections Expert Work Group. Committee Opinion No. 718: Update on immunization and pregnancy: Tetanus, diphtheria, and pertussis vaccination. Obstet Gynecol 2017;130:e153-e157.
  3. Centers for Disease Control and Prevention. Vaccinating pregnant women. Available at: https://www.cdc.gov/vitalsigns/maternal-vaccines/index.html. Accessed Nov. 18, 2019.
  4. [No authors listed]. ACOG Committee Opinion No. 772: Immunization implementation strategies for obstetrician-gynecologists. Obstet Gynecol 2019;133:e254-e259.