Supporting Universal Antenatal Pertussis Vaccination

S U P P O R T I N G U N I V E R S A LA N T E N A T A L P E R T U S S I SV A C C I N A T I O N

D R . A L L E N C H E R E R

Pertussis (Whooping Cough) is a serious healthissue, especially in the very young infant. It iscaused by a bacteria, Bordetella pertussis, and istransmitted person to person via aerosoldroplets usually by coughing or sneezing. Theillness typically begins with cold-like symptomswhich may then progress to the characteristicparoxysms of cough terminating with aninspiratory whoop.

In young infants, the illness can proceed tocyanosis, severe respiratory fatigue, apnea, andeven death. Although whole-cell and acellularvaccine formulations against B. pertussis areavailable, primary immunization generally doesnot start until 6-8 weeks and as late as 3 monthsof age in some countries, leaving the infantunprotected during a most vulnerable period.

The incidence of pertussis has steadilyincreased in the United States and elsewheresince the 1980s and especially since 2005. Since2010, 10-50,000 cases of whooping cough havebeen reported each year in the United Stateswith every state represented. More than 48,000cases were reported in 2012, and in Californiaalone, greater than 10,000 cases were reportedin 2014.

Although all ages are affected, the highest ratesof disease and hospitalization occur in infantsless than one year of age. The numbers havebeen accompanied by an alarming increase inthe number of deaths, almost exclusivelyamong infants less than 3 months of age.

One of the causes thought to explain theresurgence of pertussis is the rapid waning ofthe immunity induced by current vaccines.Prior to the 1990s, a whole-cell vaccine was usedand the immunity it induced was longer lasting.

Since then, acellular pertussis vaccines havebeen used exclusively in the United Statesprimarily due to less frequent adverse reactions.

However, these vaccines have been shown toinduce immunity which wanes rapidly over aperiod of several years. As a result, pertussisimmunization is required more frequently and thelikelihood of non-protection is much greater,especially for older children and adults. This isparticularly alarming since such persons are oftenthe caretakers and closest contacts of younginfants. Thus, when considering preventionstrategies for pertussis, it is critical to includeapproaches that prevent pertussis transmission toyoung infants.

In 2001, the Global Pertussis Initiative (GPI) wasestablished in response to the resurgence ofpertussis and in an effort to raise global awarenessabout pertussis and to develop evidence-basedrecommendations for vaccination strategies . Overthe years, the GPI has focused particular attentionon protection of the very young infant and hasemphasized as a primary strategy maternalimmunization during pregnancy which directlyprotects the infant through the passive transfer ofpertussis antibodies from mother to fetus.

Numerous studies have demonstrated that apregnancy booster (Tdap) provides the necessaryprotection to the very young from birth untilinfant-generated immunity is achieved from theprimary series of pertussis immunizations. Basedon studies that demonstrate robust maternalantibody production within 2 weeks of boosterimmunization and ready immunoglobulin transferafter 30 weeks’ gestation, currentrecommendations call for Tdap immunizationbetween 28 and 38 weeks’ gestation.

Since maternal antibody levels declinesignificantly I year post immunization and arealmost non-existent 2 years post immunization,

the Advisory Committee on ImmunizationPractices (ACIP) of the Centers for Disease Controland Prevention (CDC) in 2012 recommendedbooster immunization during every pregnancy. Todate, research finds that vaccination againstpertussis during pregnancy is well tolerated andnot associated with any adverse obstetric, birth, orneonatal outcomes.

Recently, a study from the United Kingdomevaluating antenatal booster immunization andefficacy in preterm births demonstrated with amean gestational age of 29 weeks at time ofimmunization and birth at a mean gestation of 32weeks, protective antibody levels were found atthe start of the primary immunization series.

Unfortunately, despite strong recommendationsby the CDC, the American College of Obstetricsand Gynecology, the American Academy of FamilyPhysicians, and the American Academy ofPediatrics , pertussis immunization rates duringpregnancy remain very low. Clearly, education ofcaregivers and patients must be a goal. Until anew pertussis vaccine with longer duration ofprotection is available, large-scale pertussisoutbreaks will continue and the burden of diseasewill continue to be particularly felt by the veryyoung infant.

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