WebMD Medical News
Laura J. Martin, MD
April 13, 2010 -- Military personnel and young people had higher swine flu
infection rates when the disease swept Singapore in 2009, a new study
The finding comes from an analysis of blood samples taken from nearly 3,000
people before, during, and after the H1N1 swine flu was detected in Singapore
from June to September 2009.
Scientists found variations in antibody levels in the groups tested, which
included 838 people from the general population, 1,213 military members, 558
from an acute care hospital, and 300 people (staff and residents) from
long-term care facilities.
In blood samples drawn before or early in the epidemic, high levels of
titers were found in 2.6% of the general population, 9.4% of military
personnel, 6.6% of hospital staff, and 6.7% of people at long-term care
facilities. Titer is a term used to describe the concentration of antibodies in
Researchers looked for a fourfold increase in antibody titers over time in
the second or third blood sample to indicate that a person had developed a new
case of swine flu infection during the epidemic time period. The researchers
say 13% of people in the community participating in the study developed a new
swine flu infection during the epidemic, a finding that “supports the case for
targeted vaccination in populations.”
“Our study also shows the variation in infection risks, with younger age
groups and military personnel having much higher infection rates,” the authors
write. “The lower infection rates in older participants corroborate other
The study also shows that people “with higher baseline titers have
significantly lower infection rates, perhaps indicative of protection against
2009 A (H1N1) infection.”
The researchers say the wide variations in antibody development in various
age groups suggest that interventions need to be tailored to the population at
The study is published in the April 14 issue of the Journal of the
American Medical Association.
SOURCES:News release, Journal of the American Medical Association.Chen, M. Journal of the American Medical Association, April 14, 2010;
vol 303: no 14: pp 1383-1391.
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