Updated Guidelines for Pertussis Vaccination During Pregnancy
Prevention of pertussis in infants has been a matter of great concern owing to the heavy burden of fatality. Pertussis, also known as whooping cough is a highly contagious bacterial disease characterised by uncontrollable, violent coughing. Compared with older children and adults, infants aged less than 1 year of age have substantially higher rates of pertussis and the largest burden of pertussis-related deaths.
Infants aged ≤ 2 months deserve special attention since they are too young to be vaccinated. This vulnerable age group accounts for the majority of pertussis cases, hospitalizations, and deaths. Vaccination against pertussis is provided through the combination vaccine called DPT. DPT is protective against the infectious diseases diphtheria and tetanus in addition to pertussis. At least eight variants of the DPT vaccines are available; variations are due to the type of components used. Tdap, for example contains reduced concentrations of diphtheria and pertussis antigens. The 'a' in 'ap' indicates that the acellular pertussis toxoid has been used. These modifications are meant to reduce side effects.
The Advisory Committee on Immunization Practices (ACIP), the body that provides advice and guidance on effective control of vaccine-preventable diseases in the U.S. civilian population, has updated its recommendations for use of Tdap in unvaccinated pregnant women and persons who have or anticipate having close contact with an infant aged <12 months.
Based on the available data from studies, ACIP concludes that Tdap is safe in pregnant women and causes no 'elevated frequency or unusual patterns of adverse events'. A woman vaccinated with Tdap during pregnancy is likely to be protected at time of delivery, and therefore less likely to transmit pertussis to her infant.
An infant receives protective antibodies against pertussis from its mother. It has been found that this form of protection is greater when the mother has received vaccination during or before pregnancy. Infants born to unvaccinated mothers are at risk of suffering from the infection.
A programme called cocooning has been recommended by ACIP since 2005. This is the strategy of vaccinating pregnant women immediately after delivery and all other close contacts of infants aged <12 months with Tdap to reduce the risk for transmission of pertussis to infants. Various cocooning programmes succeeded in covering postpartum mothers (postpartum-after delivery). But they had limited success in vaccinating fathers or other family members. ACIP however concludes that cocooning likely provides indirect protection to infants and firmly supports vaccination with Tdap for unvaccinated persons who anticipate close contact with an infant.
Both tetanus and diphtheria toxoids (Td) and tetanus toxoid vaccines have been used extensively in pregnant women worldwide to prevent tetanus in the new born. These vaccines when administered during pregnancy do not damage the development of embryo, i.e. they are not teratogenic.
Tdap may be administered after 20 weeks' gestation, says ACIP. Vaccination of the mother during pregnancy is more cost effective and prevents a greater proportion of infant cases and deaths than postpartum maternal vaccination.
The updated guidelines published by the ACIP are summarized below:
· Tdap vaccination has been recommended for all pregnant women who previously have not received Tdap. Tdap should be given during pregnancy, preferably during the third or late second trimester (after 20 weeks' gestation). If not administered during pregnancy, Tdap should be administered immediately after delivery (postpartum).
· Adolescents and adults (e.g., parents, siblings, grandparents, child-care providers, and health-care personnel) who have or anticipate having close contact with an infant aged <12 months should receive a single dose of Tdap to protect against pertussis if they have not previously received Tdap. Tdap should be given at least 2 weeks before beginning close contact with the infant.
· If a tetanus and diphtheria booster vaccination is indicated during pregnancy for a woman who has previously not received Tdap (i.e., more than 10 years since previous Td), then Tdap should be administered during pregnancy, preferably during the third or late second trimester (after 20 weeks' gestation).
· A tetanus toxoid-containing vaccine might be recommended for wound management in a pregnant woman if 5 years or more have elapsed since last receiving Td. If a tetanus booster is indicated for a pregnant woman who previously has not received Tdap, Tdap should be administered instead.
· Pregnant women who have never been vaccinated against tetanus should receive three doses of vaccination containing tetanus and reduced diphtheria toxoids at 0, 4 weeks, and 6 to 12 months. Tdap should replace 1 dose of Td, preferably during the third or late second trimester (after 20 weeks' gestation) of pregnancy.
Reference: Updated Recommendations for Use of Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis Vaccine (Tdap) in Pregnant Women and Persons Who Have or Anticipate Having Close Contact With an Infant Aged <12 Months; Morbidity & Mortality Weekly Report. 2011;60(41):1424-1426.