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Senior Citizens Not Getting Pneumonia Due to Vaccine
for Children
Oct. 25, 2005 - The incidence of pneumonia among
senior citizens age 65 and older, as well as all adults 50 and up, has
decreased substantially. One may assume its due to the pneumonia
vaccine, and this would be correct. But not the vaccine for older
adults. This decrease is linked to the introduction of a pneumonia
vaccine for children in 2000, according to a study in the October 26
issue of JAMA.
The pneumococcal conjugate vaccine (PCV-7) was
licensed for use in infants and young children in March 2000, according
to background information in the article. Use of PCV-7 in children can
affect pneumonia transmission in the community. Pneumonia causes
substantial illness and death among older adults. Consistent with the
ability of PCV-7 to interrupt transmission, declines in invasive
pneumococcal disease incidence among older adults were observed in 2001,
the year after PCV-7 introduction.
Catherine A. Lexau, Ph.D., M.P.H., of the Minnesota
Department of Health, St. Paul, Minn., and colleagues conducted a study
to determine whether the observed early decline among adults aged 50
years and older has continued over the 4 years since pneumococcal
conjugate vaccine licensure, whether disease characteristics have
changed, and whether the spectrum of patients acquiring invasive
pneumococcal disease has changed.
The study included population-based surveillance
data of invasive pneumococcal disease in 8 U.S. geographic areas (total
population, 18,813,000), 1998-2003.
The researchers found that the incidence of
invasive pneumococcal disease among adults aged 50 years or older
declined 28 percent, from 40.8 cases/100,000 in 1998-1999 to 29.4 in
2002-2003.
During 2002 and 2003, the overall rate of invasive
disease among persons aged 65 years or older (41.7 cases/100,000) was
lower than the Healthy People 2010 goal of 42 cases/100,000.
Among adults aged 50 years or older, incidence of
disease caused by the 7 conjugate vaccine serotypes declined 55 percent
from 22.4 to 10.2 cases/100,000.
In contrast, disease caused by any of the 16
serotypes only in polysaccharide vaccine did not change, and disease
caused by serotypes not in either vaccine increased somewhat, from 6.0
to 6.8 cases/100,000.
Between 1998-1999 and 2002-2003, the proportion of
case-patients with human immunodeficiency virus infection increased from
1.7 percent (47/2,737) to 5.6 percent (124/2,231), and those with any
co-existing illness that is an indication for pneumococcal
polysaccharide vaccination increased from 62.3 percent (1,842/2,955) to
72.0 percent (1,721/2,390).
The researchers estimate that 12,500 fewer cases
and 1,100 fewer deaths occurred among older Americans in 2002 and 2003,
compared with the numbers of cases and deaths occurring before the
vaccine was available.
"Several factors support the hypothesis that the
declines in invasive disease reported here likely occurred because of
decreased community transmission of vaccine-type pneumococci from young
children, many of whom have received PCV-7, say the authors.
Studies of pneumococcal carriage indicate that
conjugate vaccines reduce carriage of vaccine-type pneumococci in
vaccinated children. Likewise, unvaccinated children in close contact
with vaccinated children or living in communities in which the vaccine
is being used also have experienced reductions in pneumococcal carriage
and disease caused by PCV-7 serotypes.
In this analysis, the overall decline in invasive
disease incidence was mainly due to a decrease in disease caused by
PCV-7 serotypes, suggesting a specific conjugate vaccine effect.
In addition, the timing of the changes among older
adults coincided with uptake of vaccine in children; incidence first
declined in 2001, following initial use of PCV-7 among young children in
the last half of 2000, and then dropped further in 2002-2003 as vaccine
coverage in children increased.
"We have documented a consistent decrease in
incidence of invasive pneumococcal disease in an age group at high risk
for serious disease and death from these illnesses.
Policy makers elsewhere who are considering
whether to incorporate PCV-7 into their routine infant immunization
programs and who are weighing its cost-effectiveness should consider the
benefits seen in older adults. However, it is unknown whether this herd
effect will be similar in all settings and population subsets.
The size of the effect may differ in populations
with different serotype distributions or with a higher or lower
prevalence of chronic conditions among older adults. We look forward to
results from other populations to see if similar effects will occur. In
the U.S. population, use of PCV-7 for children has been an effective
means of preventing disease in older adults," the researchers conclude.
(JAMA.2005; 294:2043-2051. www.jamamedia.org)
Editor's Note: Financial support for this project
was provided in part by the CDC Emerging Infections Program.
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