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PCV7 may have reduced pneumococcal infections among White Mountain Apache population
Rate of pneumococcal infections decreased among children, remained stable among adults.
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The incidence of pneumococcal infections among White Mountain Apache children has dramatically decreased since the introduction of routine vaccination using the seven-valent pneumococcal conjugate vaccine, according to findings published recently in Clinical Infectious Diseases.
However, among children aged younger than 5 years, the rate of invasive pneumococcal disease remains almost six times greater in the White Mountain Apache population than in the general U.S. population.
Katherine O’Brien, MD, MPH, of the Johns Hopkins Bloomberg School of Public Health, addressed this disparity in an interview with Infectious Diseases in Children. She said that she is satisfied with the performance of PCV7 (Prevnar, Wyeth) in this trial. “If a product can be shown to be efficacious in a setting where the burden of disease is high, then it is almost certainly efficacious in a setting where the burden is lower,” she said. “A high burden setting sets a high bar for a vaccine’s performance.”
O’Brien also discussed how the specific concerns of this population are associated with those of the general U.S. population. “Underlying conditions related to high rates of invasive pneumococcal disease such as diabetes, cardiac disease and alcohol abuse are prevalent in this community. Reducing these conditions in this population underscores the importance of doing so in all populations,” she said.
Methods and results
The researchers from Alaska, Arizona and Maryland collected surveillance data from several hospitals on and surrounding the Fort Apache Indian Reservation in Northern Arizona from 1991 to 2006. They divided this duration into three time periods: from 1991 to 1997 was the pre-PCV7 baseline period, from 1998 to 2000 was the trial period for the vaccine, and from 2001 to 2006 was the period defined by routine immunization.
The researchers identified 246 cases of invasive pneumococcal disease during the study years. Overall, the rate of invasive pneumococcal infections decreased from 126.2 cases per 100,000 person-years during the baseline period to 86.6 cases per 100,000 person-years during the final time period.
Among children aged younger than 5 years, the rate of pneumococcal disease attributable to PCV7 serotypes of Streptococcus pneumoniae decreased by 92%, according to the researchers. The rate for non-PCV7 serotypes of S. pneumoniae decreased by 44% in the same age group. The rate for adults remained unchanged.
“There are essentially no cases of vaccine serotype invasive pneumococcal disease seen among White Mountain Apache children anymore,” O’Brien said.
Through Dec. 31, 2007, the last reported case of invasive pneumococcal disease caused by PCV7-type strains in a child aged younger than 5 years was in 2003. The researchers believe that PCV7 may have contributed to the reduction of all invasive pneumococcal infections among children in this population. However, the researchers stressed the need for vaccines with broader serotype coverage to further reduce the disparity between the rate of pneumococcal infections in the White Mountain Apache and the general U.S. population. – by Rob Volansky
For more information:
- Lacapa R, Bliss SJ, Larzelere-Hinton F, et al. Changing epidemiology of invasive pneumococcal disease among White Mountain Apache persons in the era of the pneumococcal conjugate vaccine. Clin Infect Dis. 2008;47:476-484.