The switch from the 7-valent pneumococcal conjugate vaccine, or PCV7, to the 13-valent pneumococcal conjugate vaccine, or PCV13, in children was associated with major declines in pneumococcal disease in U.S. adults, according to research published in Clinical Infectious Diseases.
Universal PCV7 immunization of birth cohorts began in 2000, and “the widespread use of the 7-valent pneumococcal conjugate vaccine among young children in the U.S. also resulted – via a herd effect – in reduced levels of [invasive pneumococcal diseases (IPD)] among older children and adults,” the researchers wrote. “However, by 2010, increasing numbers of cases of IPD due to non-vaccine serotypes began to erode the reductions in disease in both adults and children.”
In part of a response to the increased cases, “PCV13 was introduced in the U.S. for use in children in all children less than 2 years of age and as catch-up dosing for children between the ages of 2 and 5 years in 2010,” the researchers reported. “Two years later, in 2012, PCV13 was recommended for adults at least 18 years of age with immunocompromising conditions, and in 2014, the recommendation was expanded to include all adults at least 65 years of age,”
The researchers measured the impact of replacing PCV7 with PCV13 on disease burden in adults by using a retrospective design and data from two U.S. health care claims repositories. They studied the changes in rates of pneumococcal disease among U.S. adults aged 18 years and older between 2007 and 2015, stratified by age and risk profile, including healthy, at risk and high risk. Analysis was limited to hospitalized patients with pneumonia. The researchers estimated the rate ratios for 2007-2010 (pre-PCV13), 2011-2012 (peri-PCV13) and 2013-2015 (post-PCV13) to compare IPD, all-cause hospitalized pneumonia (ACHP) and pneumococcal pneumonia among three risk groups.
The study population included 56.6 million people, who amassed a total of 158.1 million person-years of observation during the study period.
The researchers reported that IPD and ACHP rates increased with age, with rates 2 to 27 times higher in people aged at least 75 years compared with those of people aged 18 to 49 years, and by comorbidity, with rates 4 to 20 times higher in the high-risk cohort compared with those of the healthy cohort.
“From pre- to post-PCV13 period, IPD rates declined 5% to 48% and ACHP rates declined 4% to 19% across age and risk groups (ACHP did not decline in persons aged 75 or older),” the researchers wrote. “The decline in IPD and ACHP was attenuated among older adults and those with comorbidities; accordingly, rate ratios among at-risk and high-risk persons (vs. healthy counterparts) increased during the peri- and post-PCV13 periods compared with pre-PCV13 period.”
The researchers concluded that their findings suggest that the switch to PCV13 was associated with large declines in IPD among all adults in the U.S., “irrespective of age and risk profile and substantial decreases in ACHP in U.S. adults in ACHP except those aged 75 years and older.”
They noted that older adults and those with comorbidities experience the highest incidence of disease.
“In the long term, we need new strategies such as expanded valency vaccines or modulation of the chronic inflammatory state associated with chronic disease and aging. In the short term, pneumococcal and influenza vaccination are recommended for prevention, and uptake of both is below recommended levels in adults.”– by Bruce Thiel
Pelton reports receiving financial support from Pfizer Inc. for participation in the study design, data analysis and data interpretation, and serving as an advisory board member for and receiving research grants from Pfizer, Merck and GSK. Please see the full study for other authors’ relevant financial disclosures.