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Pertussis (Whooping Cough) Vaccine Found Effective Only for a Few Years

Health In Focus   - G J E 4
Highlights
  • Researchers from the University of Toronto carried out a study to understand the effectiveness of acellular pertussis vaccine.
  • The vaccine lowered incidence of pertussis in Canada
  • The immunity provided by the vaccine lasts only for a period of 3 years with loss of immunity after 7 years.
The vaccine that is currently available for pertussis is highly effective for a period of three years, after which its effect dwindles, says a study by researchers from The University of Toronto.
Pertussis (Whooping Cough) Vaccine Found Effective Only for a Few Years
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Dr. Natasha Crowcroft from The University of Toronto adds "Despite waning immunity of the whooping cough vaccine, it's important to note that the number of cases of pertussis in Canada is still quite low. The most effective way parents can prevent whooping cough is to have their children immunized on time."

‘Vaccination at the right time could prevent infection.’
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The Pertussis Vaccine

The pertussis vaccine is an acellular vaccine, as it does not contain the full organism, and is used to protect against a bacterial infection that is spread by coughing or sneezing.

The current vaccine has been used in Canada since 1997 and also used in other countries like Australia, New Zealand, Europe and North America. It is administered to children, teenagers, infants and adults to prevent the incidence of pertussis.

Symptoms of Pertussis

Pertussis is also called the whooping cough because of the characteristic whoop that is heard when the patient coughs. The initial symptoms include
  • Mild fever
  • Low grade runny nose
  • Occasional cough
As the condition advances it can lead to
  • Exhaustion
  • Nausea and vomiting
  • Characteristic whoop during persistent cough
Vaccination Chart for Infants

Infants should be protected against whooping cough to avoid the severe infection that it can lead to. The following is the time of vaccination for infants
  • At 60 days after birth
  • At 120 days after birth
  • At 180 days after birth
  • Between 1 year 3 months to 1 and a half years.
  • Between 4 to 6 years
Though the current research by Dr. Crawford shows that the effectiveness of the vaccine could wane over time, she is quick to add that she doesn't want anyone to avoid taking the vaccine altogether.

Decrease in Disease Incidence after Pertussis Vaccine

  • The incidence of pertussis prior to Canada's vaccination program was 156 cases per 100 000 people.
  • After the vaccination program had started, the incidence lowered to 2 per 100 000 in 2011 to 13.9 in 2012.
This shows that the pertussis vaccine program conducted in Canada was highly effective in lowering the incidence of pertussis.

Study on Effectiveness of Pertussis Vaccine

The researchers studied 5867 people between the years between 1992 to 2013. Out of which
  • 486 tested positive for the presence of pertussis
  • 5381 were negative for pertussis
Results
  • Up to 3 years after vaccination, there was immunity against the infection.
  • 7 years after vaccination, there was little immunity.
  • The risk of getting pertussis increased by 27% every year.
When the effectiveness of the newer acellular pertussis vaccine was compared with the whole organism vaccine used in certain countries, it was found that those individuals who received the newer vaccine during the first three infant vaccinations were twice as likely to get pertussis when compared with individuals who received the whole organism vaccine.

The researchers of the study conclude by saying "... our finding that the low-effectiveness whole-cell vaccine is still better for priming than the currently used acellular vaccine nearly 2 decades after the change in practice has profound implications for understanding the effectiveness of the pertussis vaccine."

Canada changed from using the whole organism vaccine to the acellular vaccine due to poor effectiveness of the whole organism vaccine that was used earlier. However, newer whole organism vaccines that are available in the market are found to be effective.

The results of this study are supported by other studies conducted in The United States and in The U.K that have shown a decreased immunity over a period of time.

Corrective Measures

The lack of immunity after a period of 7 years is an alarming fact in the fight against pertussis. The optimum level of immunity can be maintained by
  • Vaccinating pregnant women.
  • Re-immunizing children after 7 years.
  • Re-immunizing when going to pertussis prone areas.
This study provides an insight into the corrective measures that need to be incorporated in vaccinating against pertussis in Canada. These measures will serve to provide the right defence against the disease and prevent its spread.

References:
  1. Pertussis (Whooping Cough) Vaccine - (http://www.vaccines.gov/diseases/pertussis/)
  2. Pertussis (Whooping Cough) - Signs and Symptoms - (http://www.cdc.gov/pertussis/about/signs-symptoms.html)
Source: Medindia
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