WEDNESDAY, April 5, 2006 (HealthDay News) -- The vaccine to prevent serious infections such as invasive pneumonia and meningitis has significantly reduced the rate of these illnesses, and has also curtailed the spread of antibiotic-resistant strains of pneumococcal disease in young children and adults.
A new report from the U.S. Centers for Disease Control and Prevention found that since the introduction of the pneumococcal conjugate vaccine (Prevnar) in 1999, the incidence of penicillin-resistant infection from the seven strains included in the vaccine has dropped by nearly 90 percent.
"The rates of resistant disease in young children dropped dramatically following the introduction of the conjugate vaccine. The effect of the vaccine was really quite large. In 2004, there were 13,000 fewer illnesses [caused by the strains in the vaccine] than there were in 1999," said study co-author Dr. Cynthia Whitney, chief of the respiratory disease branch at the CDC.
The findings appear in the April 6 issue of the New England Journal of Medicine.
The bacterium Streptococcus pneumoniae causes a variety of pneumococcal diseases, according to the CDC. Some are relatively mild, such as ear infections, while others are potentially life-threatening, such as pneumonia, meningitis and blood infections. Pneumococcal disease is spread from person to person through respiratory secretions. Children have an increased risk of developing pneumococcal disease.
Beginning in 2000, the pneumococcal conjugate vaccine became available for infants and children. The vaccine included the seven strains, or serotypes, of the bacteria that commonly cause pneumococcal disease in the United States.
According to Whitney, the CDC surveillance from 1998 through 2004 included about 17 million people from across the country.
The researchers found the rates of serious pneumococcal disease that were resistant to penicillin peaked in 1999, at 6.3 cases per 100,000. By 2004, that number was down to 2.7 cases per 100,000 -- a decrease of 57 percent. Rates of pneumococcal disease resistant to multiple antibiotics also dropped significantly, from 4.1 to 1.7 per 100,000 -- a 59 percent drop.
When the researchers looked specifically at the incidence of disease caused by serotypes in the vaccine, the decrease was even more significant. The rate of penicillin-resistant pneumococcal disease caused by vaccine serotypes was down 87 percent for children and adults. In children younger than 2, the incidence was down 98 percent. In adults over 65, there was a 79 percent drop in the rates of penicillin-resistant pneumococcal disease caused by conjugate vaccine strains.
However, not all the news was good. There was a slight increase in the incidence of pneumococcal disease caused by strains that weren't included in the vaccine.
"Fortunately, the amount is small, especially relative to the big drop in the other serotypes, but it's a trend we think is worth watching because this bacteria has shown an ability to adapt in the past," said Whitney.
Dr. Graham Krasan, a pediatric infectious disease specialist at William Beaumont Hospital in Royal Oak, Mich., said he expects that some of these emerging strains will likely be included in second-generation versions of pneumococcal vaccine.
"The reassuring thing is, even with emergence of these replacement strains, the incidence has still declined substantially," said Krasan. However, he did point out that the incidence of invasive pneumococcal disease is probably higher than reported because the bacteria can't always be isolated from blood samples.
However, that doesn't take away from the vaccine's success, he said.
"The pneumococcal vaccine, as predicted, is quite effective in decreasing life-threatening invasive disease in children, and in decreasing some of the penicillin non-susceptible and other antibiotic-resistant organisms," Krasan said.
Some parents had hoped the pneumococcal vaccine would decrease the rate of childhood ear infections, but Krasan said the vaccine hasn't had a dramatic effect on these less-serious infections. He said the reason is that S. pneumoniae is only one of many bacteria that can cause ear infections.
However, Whitney noted that, with the decrease in antibiotic-resistant organisms, medications may be more effective in treating these infections.
"This doesn't mean that doctors can go back to treating invasive pneumococcal disease with simple penicillin again, but with fewer resistant strains around, there will be fewer treatment complications and failures. For parents, it means when children have ear infections or pneumonia, they won't have to worry about resistant infections as much, though we all still need to be concerned about antibiotic resistance," she said.
The National Foundation for Infectious Diseases has more information on pneumococcal disease.