Tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination is recommended for all pregnant women between 27 and 36 weeks’ gestation to prevent whooping cough in infants. However, coverage among pregnant women remains low.

To find out why, California Department of Public Health researchers conducted a survey of mothers who recently delivered children. In the study reported in Morbidity & Mortality Weekly Report, the team interviewed 66 mothers, 30% of whom had received Tdap vaccine, with infants younger than age 4 months who had pertussis.

They found that women who received care at clinics stocked with Tdap vaccine were more likely to be vaccinated. On the other hand, women covered by Medicaid were less likely to be vaccinated than those with private insurance, even when treated in clinics that stocked Tdap vaccine.

“This finding is consistent with a previous survey demonstrating that receipt of influenza vaccine by pregnant women was more likely among those whose prenatal care providers offered vaccination on-site,” noted the researchers. “However, even when prenatal care providers stocked Tdap vaccine on-site, women insured by Medicaid were less likely to receive Tdap vaccination than were women with private insurance. Previous Tdap vaccination coverage estimates among pregnant women in California were also lower among those insured by Medicaid (40%) than among those with private insurance (65%).

Reasons for this disparity are not known; however, a need exists to reduce financial barriers to stocking and administering Tdap vaccine in prenatal clinics, particularly among those serving Medicaid patients.”

The researchers suggest that promoting on-site prenatal vaccination, educating providers about Tdap recommendations, and strengthening off-site referrals will likely improve Tdap vaccination coverage during pregnancy.

The study emphasizes that a recommendation by prenatal-care providers for their pregnant patients to receive Tdap is important, especially when the vaccine is not available on-site. The authors urge that pregnant patients be provided with specific information about where to get Tdap and that clinicians follow up to make sure that vaccination occurred.

In this survey, about 40% of unvaccinated mothers said that they never received a recommendation or referral for Tdap vaccine or opted not to get the vaccine for other reasons. Results indicate that 40% of unvaccinated mothers, including one who originally refused Tdap vaccination, were immunized postpartum. Of the 40 mothers not vaccinated during pregnancy, 20% refused prenatal Tdap.

Researchers cite evidence that fewer infants of mothers who were vaccinated according to recommendations required hospitalization after developing pertussis, compared with infants of unvaccinated mothers.

What was puzzling about the results, according to the report, is that vaccination was readily available to mothers who did not receive it. In California, pharmacists are permitted to provide immunizations, and all routinely recommended adult vaccines are covered by Medicaid when administered in a provider’s office or in a pharmacy. Furthermore, recent state regulations require pharmacists to notify providers of immunizations administered and to enter all doses into the California Immunization Registry, making it possible for providers to know whether vaccine referrals to pharmacies had the desired effect.

“However, stocking vaccines on-site in prenatal clinics is the best way to ensure that all pregnant women are vaccinated and reduce the incidence of pertussis among infants too young to be vaccinated,” study authors advise.

« Click here to return to Vaccine Update.