A decline in both pediatric and adult pneumonia-related hospitalizations following the 2000 introduction of the 7-valent pneumococcal vaccine, or PCV7, into the U.S. childhood immunization schedule was sustained over the next decade, a comprehensive assessment of U.S. hospitalizations showed.
The findings allay concerns about whether increases in disease caused by nonvaccine serotypes had eroded the gains made in the years following the PCV7 introduction, according to Dr. Marie R. Griffin of Vanderbilt University, Nashville, Tenn., and her colleagues.
Compared with the estimated annual rates of hospitalization for pneumonia from 1997 through 1999 (the 3 years prior to PCV7 introduction), the rates from 2007 through 2009 (the 3 years prior to a switch to 13-valent pneumococcal conjugate vaccine, or PCV13, in 2010) indicate that the annual rate among children younger than age 2 years declined by 551.1/100,000 children, or 43.2%, which translates to 47,000 fewer hospitalizations annually. The rates among adults aged 85 years or older declined by 1,300.8/100,000, or 22.8%, which translates to 73,000 fewer hospitalizations, the investigators reported in the July 11 issue of the New England Journal of Medicine.
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Since the 2000 introduction of the 7-valent pneumococcal vaccine, or PCV7, both pediatric and adult pneumonia-related hospitalizations have declined.
Although the declines were steepest in those at the "extremes of age," the rates also declined for adults aged 18-39 years, 65-74 years, and 75-84 years (by 8.4, 85.3, and 359.8/100,000, respectively), they said (N. Engl. J. Med. 2013;369:155-63).
"The overall, age-adjusted annual reduction in hospitalization rates from the pre-PCV7 years was 54.8 hospitalizations per 100,000, representing an estimated 168,000 fewer hospitalizations in 2009 than would have been expected," Dr. Griffin and her colleagues wrote.
Annual hospitalization rates for this study were estimated based on hospitalization for pneumonia from any cause as identified using the Nationwide Inpatient Sample database – the largest all-payer U.S. inpatient care database, which includes data from about 8 million hospitalizations each year. Data included in this study were for patients with a first-listed discharge diagnosis of pneumonia or a first-listed discharge diagnosis of meningitis, septicemia, or empyema in addition to a diagnosis of pneumonia.
The marked decline in pneumococcal disease among both vaccinated and unvaccinated individuals is attributable to "herd" immunity provided by PCV7, and although it was previously shown that the introduction of PCV7 had resulted in a nearly 40% reduction in pneumonia-related hospitalizations within 4 years, an increase in disease caused by nonvaccine serotypes – particularly serotype 19A – raised concerns that this "serotype replacement" represented a step backward, the investigators explained.
The findings suggest that these concerns were unwarranted.
Although the declines in hospitalization among adults was more modest and emerged more slowly than the "remarkable early declines" seen in children, they did result in "large absolute overall reductions in hospitalizations for pneumonia," the investigators said.
Still, unvaccinated age groups continue to have some residual burden of pneumococcal disease due to serotypes covered by PCV7, they noted.
"It is not known whether the direct vaccination of adults with PCV13 would prevent pneumonia in adults and whether such efforts would add substantially to the indirect benefits generated by the ongoing PCV13 vaccination program in infants, which may now be reducing the transmission of the additional six vaccine serotypes," they said.
This study was supported by grants from the Centers for Disease Control and Prevention and the Thrasher Research Fund. Dr. Griffin reported receiving grant support through her institution from Pfizer, and coauthor Dr. Carlos G. Grijalva reported receiving consulting fees from GlaxoSmithKline, and grant support through his institution from Pfizer. The remaining authors reported having no relevant financial disclosures.