TUESDAY, April 11, 2006 (HealthDay News) -- It shields children and adults from pneumonia, meningitis and blood infections and now a new study finds the pneumococcal vaccine protects newborns, too.
Even though newborns don't receive the vaccine until after 2 months of age, immunization of older siblings and adults may be keeping them from getting sick, researchers report in the April 12 issue of the Journal of the American Medical Association.
The study found that babies under 90 days old have developed fewer infections since the vaccine was introduced for use in American children six years ago.
"Children between the ages of two and 23 months of age need to get the pneumococcal disease vaccine. They benefit tremendously from it, as do younger infants and even their grandparents," said the study's lead author, Dr. Katherine Poehling, an assistant professor of pediatrics at Vanderbilt University School of Medicine.
Pneumococcal disease is cause by Streptococcus pneumoniae bacteria. The bacteria can cause a variety of diseases, including ear infections, pneumonia, meningitis and the blood infection bacteremia. The more serious disorders, such as pneumonia, meningitis and bacteremia, are often referred to as "invasive pneumococcal disease."
It's precisely these forms of the disease that the vaccine was developed to protect against. Called the pneumococcal conjugate vaccine (PCV7), the shot was added to the routine U.S. immunization schedule in 2000 for children as young as 2 months old. The current vaccine protects against the seven strains, or serotypes, of pneumococcal disease that commonly cause infections in the United States, according to the U.S Centers for Disease Control and Prevention.
For the new study, researchers included data from nearly 800,000 infants from eight states with active pneumococcal disease-surveillance sites. From that large group, they found 146 confirmed cases of invasive pneumococcal disease.
Eighty-nine cases occurred during the three years prior to the introduction of the vaccine, and only 57 occurred during the three years after the vaccine's introduction. That means that before the vaccine, there were about 12 cases of invasive pneumococcal disease per 100,000 live births, but only about 7 per 100,000 births after the introduction of the vaccine, the study found.
Overall, the rate of invasive pneumococcal disease dropped by 39 percent for infants under 30 days old, 45 percent for babies between 31 and 60 days, and 32 percent for those between 61 and 90 days old.
"These data are the first to suggest that neonates and infants too young to receive PCV7 are benefiting from 'herd immunity.' Herd immunity occurs when vaccinated persons in a population indirectly protect unvaccinated members by impeding the transmission of the infectious agent in the population," the study authors wrote.
The authors also found a steep drop in the incidence of pneumococcal disease among black infants -- from a pre-vaccine level of 17 cases per 100,000 births to just 5.3 cases per 100,000 after the introduction of the vaccine. Black infants had previously had a significantly higher incidence of invasive pneumococcal disease than whites, but the current decline has eliminated that racial difference, the study authors said.
Dr. Graham Krasan, a pediatric infectious disease specialist at William Beaumont Hospital in Royal Oak, Mich., called the study "interesting, because it addresses the question of whether vaccinating a target population with a high prevalence of colonization can positively impact other populations that aren't vaccinated." According to Krasan, this study shows that it can.
Not all the news was good, however. The incidence of invasive disease from several pneumococcal strains that aren't included in the vaccine rose in the three years after the vaccine's debut.
Poehling said, "There's always the potential that some of the serotypes not included in the vaccine will become prominent. If that happens, the strategy would be to add that to the vaccine."
Krasan added that "serotype shifts may take a long time to see on a community scale, so it's an open question if those increases are important."
There's more on the pneumococcal vaccine at American Academy of Family Physicians.