While the measles outbreak was making headlines around the country, another vaccine related outbreak was already an epidemic.
In the last five years, state health officials twice declared whooping cough (also known as pertussis) an epidemic – once in 2010 and again in 2014. Eleven thousand people were sickened and three infants died.
Whooping cough is a serious infection of the respiratory system caused by bacterium. It is easily spread from person to person.
Symptoms include runny nose, nasal congestion, fever and severe coughing that can sometimes end in the “whooping” sound when a person gasps for air.
Pertussis mainly affects infants younger than 6 months old before immunizations, and kids 11 to 18 years old whose immunity has started to fade.
Although whooping cough can also make adults very ill, sometimes leading to pneumonia and hospitalization, another major concern is that adults are the most common source of infection in infants.
An analysis of a recent whooping cough epidemic in Washington state shows that the effectiveness of the Tdap vaccine (tetanus, diphtheria and pertussis) used to fight the illness waned significantly over time.
For adolescents who received all their shots, effectiveness within one year of the final booster was 73 percent. The effectiveness rate plummeted to 34 percent within two to four years.
The vaccine has changed over the years and those changes may be responsible for the fading effectiveness. The pertussis protection is from the acellular pertussis vaccine. It was introduced in 1997 to replace the whole-cell vaccine, which caused more side effects. Monday's report confirms earlier analysis that the acellular pertussis vaccine may be safer, but less effective, than the old one.
The latest analysis does not mean or even suggest that children and adults should not get the pertussis vaccine. Someone who is vaccinated, but becomes sick with whooping cough, should have a less severe course of illness. The Tdap vaccine is also recommended for college students who did not receive the vaccine as a preteen or teen.
The authors said that new vaccines are "likely needed to reduce the burden of pertussis disease." But Dr. Art Reingold, who leads the CDC's Advisory Committee on Immunization Practices group on pertussis, said he doesn't know of any pertussis vaccine development in the pipeline.
An added dose doesn’t seem to help either according to research that was presented to the ACIP group. "(An additional dose) would have very little impact on pertussis," Reingold said, "in terms of cases prevented."
Unvaccinated babies are at the highest risk for whooping cough. Since infants can’t be vaccinated until they are 2 months old, the Centers for Disease Control and Prevention (CDC) recommends that women get the Tdap vaccine during the last trimester of their pregnancy.
"Babies will be born with circulating antibodies," Reingold said, "and there's pretty good evidence that that will reduce the risk of hospitalization and death in babies."
Reingold also drew an interesting distinction between measles and pertussis having to do with herd immunity. If a large enough percentage of the population is immunized against measles, both individuals and the broader community are protected against outbreak. That's because the measles vaccine protects you against the virus that actually causes the measles illness.
But in pertussis, toxins that are released by bacteria cause the disease. The pertussis vaccine protects you against those toxins, but may not prevent you from spreading the bacteria to others — and causing illness in them.
While the vaccine is helpful in reducing symptoms, Reingold believes that "Pertussis is not going to go away with the current vaccine."
Sometimes there can be a bit of confusion between the DTaP and Tdap vaccines; the letters are similar and they are used to help prevent the same diseases.
DTaP is the vaccine that helps children younger than 7 - years - old develop immunity to diphtheria, tetanus and pertussis. Tdap is the booster immunization given at age 11 that offers continued protection.
The Tdap vaccine is the one discussed in this study published in the journal Pediatrics.
Sources: Lisa Aliferis, http://www.npr.org/blogs/health/2015/05/05/404407258/whooping-cough-vaccines-protection-fades-quickly