Vaccine responses in infants after acellular pertussis vaccination during pregnancy in Thailand
BACKGROUND: Current pertussis immunization strategies fail to protect infants younger than the starting age of a primary immunization schedule. Increasing the load of maternal antibodies is the only way to offer passive temporary protection from birth. Vaccination during pregnancy is already used as a strategy in some industrialized countries to close the pertussis susceptibility gap in young infants.
GAP: High titers of maternal antibodies do not seem to interfere with infant immune responses to acelullar pertussis (aP) vaccines, yet little is known on possible interference with whole cell (wP) pertussis vaccines used in young infants.
1) Interference of high titers of maternal pertussis-specific antibodies with humoral responses in the infant could be expected after a primary series of 3 vaccines, when wP vaccines are used in contrast to when aP vaccines are used.
2) Functionality of the antibodies in infants after vaccination in the presence of maternal antibodies may be affected by these maternal antibodies and the used vaccine.
METHODS: A randomized controlled prospective cohort study is conducted involving 370 Thai pregnant women. They receive an aP containing vaccine during pregnancy and the offspring is vaccinated with either aP or wP vaccine and is followed up until one month after the booster dose, given at the age of 18 months.
RESULTS: The reactogenicity of Tdap vaccine administered during pregnancy was not affected by prior tetanus toxoid immunization. High transplacental antibody against B. pertussis antigens in the cord blood provides evidence of antibody transfer and should thus help to protect newborns from pertussis during early life. Interference with infant immune responses to wP vaccination is reported in the presence of high titers of maternal antibodies. The effect diminishes after a booster vaccination with a wP vaccine in the second year of life.
IMPACT: Vaccinating pregnant women with an aP containing vaccine offers high titers of maternal antibodies from birth until vaccination. Interference of a large amount of maternal antibodies with wP infant vaccination is confirmed but disappears after a booster dose. Therefore, recommendation of this strategy can be considered to be safe and effective in countries using wP vaccines in infants as well, taking into account the blunting effect. If functionality of infant antibodies to pertussis is higher when different vaccines are used in mother and child, the present study will even support the use of heterologous vaccines.
Human, Pertussis, Pregnancy, Vaccine