Understanding Pertussis Infection
Pertussis, or whooping cough, is a respiratory disease caused by the bacterium Bordetella pertussis. The infection spreads through the air when an infected person coughs or sneezes. Symptoms usually start as a mild cold, but progress to a severe cough, which may be accompanied by a high-pitched “whoop” sound when breathing. Pertussis can last for more than 100 days, and individuals of all ages are at risk of contracting the disease.
The Impact of Pertussis on Babies
Whooping cough can cause life-threatening complications, especially in infants under 6 months old. Babies with whooping cough may not cough at all, but the infection can cause them to stop breathing and turn blue. Half of babies with whooping cough end up in the hospital, and of those who receive treatment, 1 out of 4 will develop pneumonia and 1 or 2 out of 100 will die.
Prevention of Pertussis Infection
Vaccination is the best way to prevent pertussis infection and build immunity. In Hong Kong, pertussis vaccination (dTap) is given to all newborns at 2, 4, and 6 months of age, with booster dosages at 18 months and primary 1 & 6. This vaccination program has been highly effective in reducing whooping cough infections in Hong Kong. However, newborns are not protected during the first 2 months after birth as they are too young to receive the vaccine.
Benefits of Whooping Cough Vaccination for Pregnant Women
Vaccinating pregnant women can protect them from pertussis infection during pregnancy and pass protective antibodies to the fetus through the placenta. This provides passive immunity to the newborn baby before they receive the vaccine at 2 months of age.
Timing and Side Effects of Whooping Cough Vaccination for Pregnant Women
Pregnant women should receive whooping cough vaccination between gestation weeks 26-34. Most women experience no discomfort or side-effects, but potential side-effects include redness, swelling, or pain at the injection site, as well as fever, fatigue, and body aches, though they are usually mild.
Late Vaccination and Timing for Optimal Protection
Protective antibodies are at their highest level about 2 weeks after vaccination, and it takes time for them to pass to the fetus. Based on studies, dTap vaccination between gestation weeks 27-36 can lower the risk of whooping cough in babies younger than 2 months old by 78%. Pregnant women in Hong Kong are suggested to vaccinate within gestation weeks 26-34 6/7, but they can still receive the vaccine after 34 6/7 weeks if they have not done so earlier.
Postpartum Vaccination for Unvaccinated Mothers
Mothers who have not received pertussis vaccine during pregnancy should receive one dose of dTaP as soon as possible after delivery, preferably before discharge from the hospital. This protects the mother from infection during the postpartum period, which can be transmitted to the newborn baby. The mother can also pass antibodies to the baby through breastfeeding, though the efficacy of postpartum vaccination is not as good as antenatal vaccination.
Vaccination for Babies
Babies need to receive their own active immunization at 2 months of age, even if they received passive immunity from their mother.
Who Should Not Be Vaccinated
Those who have had a severe allergic reaction to any vaccine component or a previous dose of pertussis-containing vaccine