whooping cough and vaccination

1. What is pertussis infection?

Pertussis is a disease caused by the bacterium Bordetella pertussis. It is an airborne infection, meaning that an infected person can spread the diseases to others through coughing or sneezing. The incubation period, that is between the timing of contracting the bacteria to onset of symptoms, is 7 to 10 days. The initial symptoms are usually similar to those of common cold, such as runny nose, fever and mild cough. These are usually followed by severe cough, and even a high-pitched “whoop” when breathing. This phenomenon may last for more than a hundred days. Individuals of all ages are at risks of being infected by this condition.

2. How does pertussis affect the baby?

Whooping cough can cause serious and sometimes life-threatening complications in babies. This is especially true within the first 6 months of life. It is important to know that many babies with whooping cough may not cough at all. Instead it may cause them to stop breathing and turn blue. About half of babies who get whooping cough end up in the hospital. Of those babies who get treatment for whooping cough in a hospital, about 1 out of 4 will develop pneumonia and 1 or 2 out of 100 will die.

3. How to prevent pertussis infection?

Beside avoiding contact of the disease, vaccination is the best way to prevent pertussis infection by building up the immunity. In Hong Kong, pertussis vaccination, together with diphtheria and tetanus vaccination (dTap) are given to all new-born babies at the age of 2 months, 4 months and 6 months. Booster dosages are further given at the 18 months of age, and when the children reach primary 1 & 6 later. This vaccination programme has been shown to be very effective in reducing whooping cough infection in Hong Kong. However, for the first 2 months after birth, new-born babies are not protected as they are not yet old enough to receive the first dose of whooping cough vaccination.

4. What are the benefits of pregnant women having whooping cough vaccination?

Vaccination of pregnant women can protect them from pertussis infection during pregnancy. Protective antibodies from vaccination can also pass to the fetus through the placenta so that the new born babies will have a passive immunization before they receive the vaccine at 2 months of age.

5. When are pregnant women usually vaccinated against whooping cough? Are there any side effects?

Pregnant women can receive whooping cough vaccine at gestation 26-34 weeks. Most women have no discomfort or side-effects after vaccination. Potential side-effects include redness, swelling or pain at injection site, fever, fatigue and body ache, but they are usually mild.

6. Can pregnant women be vaccinated after 26 to 34 weeks of pregnancy? Why is 26 to 34 weeks the most suitable time?

Protective antibodies are at their highest level about 2 weeks after getting the vaccine, and it also takes time for them to pass to the fetus. Based on studies, dTap vaccination between 27 to 36 weeks of pregnancy can lower the risk of whooping cough in babies younger than 2 months old by 78%.

In Hong Kong, pregnant women are suggested to vaccinate within gestation 26-34 6/7weeks, but they can still have vaccination after 34 6/7 weeks in case they have not had the chance to do so earlier.

7. For mothers who have not been vaccinated before delivery, can the vaccination after birth decrease the risk of infection of the babies?

For women who have not received any pertussis vaccine during pregnancy, they are recommended to receive one dose of dTaP as early as possible after delivery, preferably before discharge from hospital. This can help protect mother from infection during the postpartum period, hence avoiding transmission to the newborn baby. Also, she can pass some antibodies to the baby via breastfeeding. The efficacy of postpartum vaccination is not as good as antenatal vaccination.

8. Does baby need to be vaccinated against whooping cough after birth?

Yes. The vaccine-induced antibodies from the mother decrease with time and it is a passive immunisation. The baby still needs to receive his/her own active immunisation at 2 months of age.

9. Who are NOT suitable for vaccination against whooping cough?

  • Those who had severe allergic reaction to any vaccine component (including antibiotics or preservatives).
  • Those who had severe allergic reaction after a previous dose of pertussis-containing vaccine.
  • Those who developed encephalopathy (e.g. coma, decreased level of consciousness, prolonged seizures) not attributable to another identifiable cause within 7 days of administration of a previous dose of pertussis-containing vaccine.
This article is contributed by Dr. T.N. Danny Leung
updated on 28.12.2022