http://www.ama-assn.org/sci-pubs/amnews/pick_02/hlsb0527.htm

Whooping cough on rise; vaccine waning over time


Health officials are struggling to control outbreaks while facing limited 
vaccine supplies.

By Victoria Stagg Elliott, AMNews staff. May 27, 2002. Additional information

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Public health officials around the world are warning of a global re-emergence of whooping 
cough. State health officials across the United States are reporting that the incidence peaks 
that characterize the three- to five-year cycles of whooping cough occurrence get higher 
every time. 
And the disease is on the rise in several European countries, said researchers presenting 
data at the European Clinical Congress of Clinical Microbiology and Infectious Diseases 
in Milan last month. 
"It's a big problem, and everyone is concerned it's going to become a bigger one," said 
George A. Pankey, MD, director of infectious disease research at the Ochsner Clinic 
Foundation in New Orleans. 
Reasons for the re-emergence are unclear. Some public health officials suspect that 
because more physicians and public health workers are looking for whooping cough that 
more is being found. Scientists theorize that the bacteria may have become more virulent 
and learned to evade the vaccine, although there is little evidence to support that idea. 
Other experts suggest that the highly contagious nature of the pertussis bacteria combined 
with weaknesses in the vaccine might be to blame. The vaccine's effectiveness wanes over 
time. Most people are left unprotected within a decade of their last booster. 
Arkansas, for example, is in the middle of an outbreak that has already made more than a 
thousand junior high and high school students sick. Local health officials say nearly all of 
those children had received the required vaccine series. 


Because the pertussis vaccine's effectiveness wanes over 
time, many adults may be unprotected. 

"It wasn't that they weren't vaccinated," said Sandra Snow, MD, medical director of 
communicable diseases and immunizations for the Arkansas Dept. of Health. "But their 
immunity had waned." 
Others theorize that changes in the environment are responsible for the incidence increase. 
Some think that when the vaccine first started being used in the 1940s, people would 
receive natural boosters from periodic exposure to pertussis in the environment. But with 
less of the bacteria around, people are left without these natural boosters when they 
finally come into contact with the bacteria. 
"We don't know," said Jan Pelosi, MPH, director of the immunization division of the 
Texas Dept. of Health. "The peaks on the graph keep getting higher. We expect increases 
every three years, but not like this. We haven't had any changes in our reporting system, 
so it's not that. I think we have a true increase in cases." 

Trying to get a grip

Physicians and public health officials are thinking about ways to control the infection 
better, including the possibility of vaccinating adults and adolescents. Many outbreaks 
begin in these groups and then trickle down to children, sometimes killing infants who 
may not be old enough to have received the full vaccination series. 
This option is controversial for several reasons. The vaccine is only approved for use in 
those younger than 7 because it is unclear whether the benefits to adults and adolescents 
outweigh the risks of adverse reactions. There are clinical trials under way to attempt to 
answer this question. 
"If those studies do indeed show side effects in adults are low, we'll probably see 
somebody trying to add it to the tetanus booster," said Patricia Quinlisk, MD, MPH, 
epidemiologist with the Iowa Dept. of Health. 
Public health officials and physicians alike say that there is no point contemplating 
expanding immunization recommendations until there is enough vaccine for children. 
With the vaccine's shortage expected to continue until year's end, the Centers for Disease 
Control and Prevention recommend deferring the last two doses of the five-dose series 
until sufficient supplies are available. 
Back to top.

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 ADDITIONAL INFORMATION: 
Counting whoops


*	1,010 confirmed cases of whooping cough in 1976 (lowest rate ever) 
*	7,867 confirmed cases in 2000 
*	260,000 confirmed cases in 1934 (highest rate historically) 

Source: Centers for Disease Control and Prevention