Pneumococcal vaccination has been associated with declines in pneumonia in both vaccinated and unvaccinated persons. In a new study from the CDC, U.S. hospitalizations for pneumonia were assessed before and after the initiation of the 7-valent pneumococcal vaccination program in children.
Pneumococcal pneumonia accounts for 20 to 60% of community-acquired of pneumonia.
• When was the 7-valent pneumococcal vaccine introduced and what effect did it have?
The introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) into the U.S. infant immunization schedule in 2000 resulted in major reductions in the incidence of invasive pneumococcal disease in all age groups. The marked decline in disease among unvaccinated persons in addition to those who were vaccinated is attributable to the indirect, or “herd,” protection provided by PCV7. By preventing the acquisition and carriage of vaccine serotypes in the nasopharynx of vaccinated children, PCV7 interfered with this key step in the pathogenesis of pneumococcal disease and reduced the transmission of vaccine serotypes.
• What did this study demonstrate about the rates of hospitalization for pneumonia among children in the study period?
Whereas rates of hospitalization for pneumonia among children younger than 2 years of age declined substantially after the introduction of PCV7 in 2000, rates of decline among older children were much lower and stable throughout. Most of the decline in hospitalizations among young children occurred soon after the introduction of PCV7. The decline was sustained through the late PCV7 years, and rates for children younger than 2 years of age and those 2 to 4 years of age were lower in the late PCV7 years than in pre-PCV7 years. Rates of decline among children 5 to 17 years of age were the lowest of those in all age groups and changed little over the study period.
Morning Report Questions
Q: What effect did childhood vaccination with PCV7 have on the adult population?
A: Hospitalization rates for pneumonia in most adult age groups also appeared to decline beginning in 2000. For adults 65 years of age or older, rates declined progressively, and rates in the late PCV7 years were lower than those in pre-PCV7 years. Soon after PCV7 was introduced, small declines occurred among adults 18 to 39 years of age, and rates in the late PCV7 years remained significantly lower than those in pre-PCV7 years for this age group; however, the rates actually increased modestly among adults aged 40 to 64 years of age.
Q: What was the estimated reduction in invasive pneumococcal disease in adults and in children seven years after the introduction of the PCV7 vaccine?
A: Before the introduction of PCV7, vaccine serotypes caused 80% of invasive pneumococcal disease in young children. The proportion of invasive pneumococcal disease caused by vaccine serotypes was considerably lower in adults, but it increased with increasing age, reaching 51% in those 85 years or older. Seven years after the introduction of PCV7, invasive pneumococcal disease caused by vaccine serotypes was almost eliminated in children younger than 5 years of age and declined by more than 85% in all unvaccinated age groups. Total cases of invasive pneumococcal disease, which include cases caused by vaccine serotypes and cases caused by nonvaccine serotypes, declined by 76% among children younger than 5 years of age and by43%, 40%, 18%, and 37% among persons 5 to 17 years of age, 18 to 49 years of age, 50 to 64 years of age, and 65 years of age or older,respectively. These total reductions in invasive pneumococcal disease encompass the decline in vaccine-serotype disease and the increase in nonvaccine serotype disease.