Medical Tribune September 2008 SFV
David Brill
The influenza vaccine appears to be
less effective than previously thought
at preventing pneumonia among the
elderly.
Research published recently in The Lancet
found that US senior citizens who were
vaccinated were no less likely to get community-
acquired pneumonia during flu
season than those who were not. [2008 Aug
2;372(9636):398-405]
The findings prompted a leading infectious
diseases expert in Singapore to call for
more studies into the efficacy of the vaccine
and the causes of pneumonia – a common
complication of influenza.
The study was conducted at the Group
Health Center for Health Studies in Seattle,
US. Lead author Dr. Michael Jackson said
that for the time being doctors should continue
to encourage their older patients to
get the flu jab.
“We know it’s effective in younger,
healthy seniors. We don’t know how effective
it is in the older seniors and seniors that have
chronic medical problems but it’s a very low
risk vaccine with an extremely low rate of side
effects so even a small amount of protection,
if it’s there, is beneficial,” said Jackson,
who is presently an epidemiologist at the US
Centers for Disease Control and Prevention.
The study could have two different interpretations,
the authors wrote. It is currently
unclear whether the vaccine is ineffective
at preventing influenza infection among
people who are at risk of pneumonia, or
whether influenza infection is only responsible
for a small proportion of pneumonias
in this group.
“The controversy calls for additional
studies to assess vaccine effectiveness, improve
understanding about causes of pneumonia
in elderly individuals and the impact
on health secondary to influenza illness not
restricted to pneumonia,” said associate professor
Leo Yee Sin, clinical director of the
Communicable Disease Centre in Singapore.
She noted, however, that conducting
randomized control trials could be difficult
given the ethical problems associated with
not vaccinating certain people.
Leo added that current recommendations
for vaccine strategy are “under intense
review,” as mortality studies have failed to
show that influenza-related deaths actually
decrease as vaccine coverage increases.
The paper by Jackson et al. was a nested
case-control study involving 1,173 confirmed
cases of pneumonia and 2,346 controls,
selected from a population of immunocompetent
seniors aged 65 to 94, who were
enrolled in a health maintenance organization
in Washington state, US.
Observational studies had previously
found that the influenza vaccine reduced
the odds of being admitted for pneumonia,
but were typically based on the International
Classification of Disease codes that are
assigned to a patient’s visit. These studies
did not adjust for important health differences
between vaccinated and unvaccinated
participants and were therefore subject
to confounding.
As a result these studies have tended to
overestimate the efficacy of the vaccine, Jackson
said. His research addressed these issues
by reviewing medical records to identify
more detailed patient information, which
could then be taken into account in risk adjustment
models.
When applying a fully adjusted model
– controlling for smoking history, previous
pneumonia episodes and use of corticosteroids
and bronchodilators, among other
factors – the odds ratio for developing pneumonia
during influenza season was 0.92
among those who had been vaccinated (95
percent CI 0.77 – 1.10; P=0.35).
David Brill
The influenza vaccine appears to be
less effective than previously thought
at preventing pneumonia among the
elderly.
Research published recently in The Lancet
found that US senior citizens who were
vaccinated were no less likely to get community-
acquired pneumonia during flu
season than those who were not. [2008 Aug
2;372(9636):398-405]
The findings prompted a leading infectious
diseases expert in Singapore to call for
more studies into the efficacy of the vaccine
and the causes of pneumonia – a common
complication of influenza.
The study was conducted at the Group
Health Center for Health Studies in Seattle,
US. Lead author Dr. Michael Jackson said
that for the time being doctors should continue
to encourage their older patients to
get the flu jab.
“We know it’s effective in younger,
healthy seniors. We don’t know how effective
it is in the older seniors and seniors that have
chronic medical problems but it’s a very low
risk vaccine with an extremely low rate of side
effects so even a small amount of protection,
if it’s there, is beneficial,” said Jackson,
who is presently an epidemiologist at the US
Centers for Disease Control and Prevention.
The study could have two different interpretations,
the authors wrote. It is currently
unclear whether the vaccine is ineffective
at preventing influenza infection among
people who are at risk of pneumonia, or
whether influenza infection is only responsible
for a small proportion of pneumonias
in this group.
“The controversy calls for additional
studies to assess vaccine effectiveness, improve
understanding about causes of pneumonia
in elderly individuals and the impact
on health secondary to influenza illness not
restricted to pneumonia,” said associate professor
Leo Yee Sin, clinical director of the
Communicable Disease Centre in Singapore.
She noted, however, that conducting
randomized control trials could be difficult
given the ethical problems associated with
not vaccinating certain people.
Leo added that current recommendations
for vaccine strategy are “under intense
review,” as mortality studies have failed to
show that influenza-related deaths actually
decrease as vaccine coverage increases.
The paper by Jackson et al. was a nested
case-control study involving 1,173 confirmed
cases of pneumonia and 2,346 controls,
selected from a population of immunocompetent
seniors aged 65 to 94, who were
enrolled in a health maintenance organization
in Washington state, US.
Observational studies had previously
found that the influenza vaccine reduced
the odds of being admitted for pneumonia,
but were typically based on the International
Classification of Disease codes that are
assigned to a patient’s visit. These studies
did not adjust for important health differences
between vaccinated and unvaccinated
participants and were therefore subject
to confounding.
As a result these studies have tended to
overestimate the efficacy of the vaccine, Jackson
said. His research addressed these issues
by reviewing medical records to identify
more detailed patient information, which
could then be taken into account in risk adjustment
models.
When applying a fully adjusted model
– controlling for smoking history, previous
pneumonia episodes and use of corticosteroids
and bronchodilators, among other
factors – the odds ratio for developing pneumonia
during influenza season was 0.92
among those who had been vaccinated (95
percent CI 0.77 – 1.10; P=0.35).
No comments:
Post a Comment