Pertussis (Whooping Cough) Prevention

Dr. Parang Mehta, MD.

Whooping cough is a highly infectious disease, with a secondary attack rate of 97%.  This means that almost all susceptible people exposed to a person with whooping cough will go on to develop the disease.

Who's not susceptible?  If someone has had whooping cough recently, or been vaccinated recently, they're immune.  Immunity to whooping cough is not lifelong.  It starts waning after 5 years, and is almost non-existent after 12 years.  In countries where this disease is common, people keep getting the infection, and this keeps boosting their immunity.  In countries like America, where the disease is rare, most adolescents and adults are susceptible to whooping cough.

It is well to remember that it was the most common infectious disease cause of death in children, before vaccination was introduced.  Measures to prevent spread of the disease from persons with whooping cough, as well as vaccination of children with the vaccine, continue to be important.

Preventing Whooping Cough Spread

Children with whooping cough should be isolated, to prevent spread of the disease to other children in school and daycare.  Keeping other children in the home safe is more difficult -- they can be protected by giving protective antibiotics (see sidebar).

Isolation is needed till the child is infective.  If antibiotics (usually erythromycin) have been prescribed, the child is non-infective after 5 days, and isolation can be relaxed.

Met Someone With Whooping Cough?

Whooping cough is both highly infectious and troublesome.  Persons who have this disease cough a lot, spreading the bacteria in cough droplets into the air.  Any child who has come in close contact with an affected person (home, school, creche, daycare, etc) is likely to be infected and get the disease.

Children who have received pertussis vaccine doses in the past, should have their series completed.  However, even fully immunised children who come into contact with whooping cough at home, daycare, or school must be given protective antibiotics.

The usual recommendation is erythromycin for 2 weeks, because there is good evidence of its effectiveness.  Other choices are azithromycin and clarithromycin.

What is Infectiousness?

Infectiousness of a disease refers to the possibility of people exposed to the disease to later develop that disease.  Dangerous diseases like hepatitis B and AIDS are poorly infectious, because they are only transmitted by blood contact, or by sexual activity.

On the other hand, viral colds and chicken pox are very infectious, because the person with the disease is releasing large number of viruses into the air around him by coughing and sneezing.  Other children can get the disease by simply being in the same classroom as him for a school day.  

Secondary attack rate is the proportion of susceptible persons exposed to a particular disease who will get the disease.  For example, if there are a hundred children in a class, and forty have been vaccinated against pertussis, then the number of susceptibles if sixty.

Though pertussis is highly infectious, the champion is probably measles, with a secondary attack rate approaching 100%.  Chicken pox in the home setting is almost as bad, but this falls to 60-70% in the school setting.

Whooping Cough Vaccination

Whooping cough (Pertussis) vaccination is a part of the childhood vaccinaiton schedule in almost all countries, though the timing and number of doses differ.  It is available in various combinations with tetanus, diphtheria, injectable poliomyelitis, Hemophilus influenzae type b, and hepatitis B vaccines.  Three doses are given in the first year, starting at 6-8 weeks of age, at intervals of 4-8 weeks.  Two boosters are generally recommended, one each in the second and fifth year.

Two types of pertussis vaccines are available.  The older, whole cell vaccine, has been in use for many decades.  The newer one, called acellular partussis vaccine, is a recent introduction.  Combinations of the whole cell vaccine with diphtheria and tetanus vaccines are called DTP or DTwP, combinations of the acellular vaccine are called DTaP.  Acellular pertussis vaccine is not more effective than the whole cell vaccine, but it has fewer side effects.

Whooping cough vaccination is often associated with side effects, mostly pain, swelling, and redness at the injection site.  This can last up to 24 hours, and is more severe with the boosters in the second and fifth years.  It can be treated with fever and pain medicines.  Other side effects are high fever, seizures, excessive crying, and a limp unresponsive state after the injection.  The last three are contraindications for further doses of this vaccine.  

Whooping cough (Pertussis)

 

Last Revision: May 22, 2020