Featured Research

from universities, journals, and other organizations

Benefits Of Flu Vaccine Substantially Overestimated Says Study

Date:
December 21, 2005
Source:
University of Bristol
Summary:
Studies of influenza vaccine effectiveness in elderly people substantially overestimate vaccine benefits, according to new research from the US published today in the International Journal of Epidemiology (IJE), edited at the University of Bristol.

Studies of influenza vaccine effectiveness in elderly people substantially overestimate vaccine benefits, according to new research from the US published today in the International Journal of Epidemiology (IJE), edited at the University of Bristol.

Research by Dr Lisa Jackson and colleagues at Group Health Co-operative, Seattle, found evidence of serious bias in estimates of influenza vaccine effectiveness in seniors. Their study suggests that the association between vaccination and risk of death is influenced by the fact that relatively healthy seniors (that is, those already less at risk from dying) are more likely to get vaccinated.

However, the research does not indicate that there is NO benefit in vaccinating the elderly, just that the differences in health between seniors who receive vaccine and those who do not make it difficult or impossible to tell what benefit is being derived from the vaccine.

A commentary on the papers also published today in the IJE argues that there are reasons to seek ways to augment current vaccination strategy, for example, vaccinating health care workers, nursing home personnel and school children, who are the major spreaders of flu within the community. This would further decrease flu deaths in the elderly by reducing transmission of the virus. It could be done while better vaccines for the elderly are developed along with the use of new technologies to better evaluate effectiveness.

Dr Jackson and colleagues studied 73,527 people aged 65 and over during an eight year period. They evaluated the association of flu vaccination and risk of death, and the association of flu vaccination and risk of hospitalisation for pneumonia, in periods before, during and after flu season.

Since a protective effect of vaccination should be specific to flu season, they would expect to find reductions in risk of death or hospitalisation during the season. However, they found the greatest reductions in the period before flu season when there should be no true vaccine effect.

The reductions in risk before flu season suggest the presence of bias -- due to preferential receipt of vaccine by relatively healthy seniors -- on the estimates of flu vaccine effectiveness observed during flu season.

The researchers then looked at 252 people aged over 65 who had died during a flu season and 572 age-matched controls. Using the subjects' medical records, they identified people with 'functional limitations', such as requiring assistance to walk or bathe.

They found that functional limitations were associated with both an increased risk of death and a decreased likelihood of influenza vaccination, and so may confound the association of influenza vaccination and risk of death.

In a commentary on the studies, Professor Paul Glezen of Baylor College of Medicine, Houston said: "During the period from 1989 to 1997 the vaccination rate for people aged over 65 in the US increased from 30 to 67 per cent. Despite this increase, mortality and hospitalisation rates continued to increase rather than decline as would be expected if the vaccine was optimally effective.

"The study by Dr Jackson and her colleagues concludes that elderly people who choose to take the vaccine are, contrary to the findings of earlier cohort studies, in better health than those who fail to get the vaccine. This suggests that better studies of the benefits of flu vaccine in elderly and other high-risk groups are necessary to guide strategies for flu control.

"In the meantime, other strategies should be considered in addition to vaccinating the elderly. Many studies have shown that school children have the highest rates of flu infection each year and that they are the major spreaders of flu in the community and introducers into the household. Immunization of school children, therefore, would reduce exposure of vulnerable patients to flu.

"One of the problems with current vaccination strategy is that high-risk persons are relatively inaccessible; no improvement in vaccine coverage has occurred since 1997. School children could be accessible through school-based vaccine clinics allowing rapid administration of vaccine to large numbers, representing all socioeconomic groups, within a short period of time."



Story Source:

The above story is based on materials provided by University of Bristol. Note: Materials may be edited for content and length.


Cite This Page:

University of Bristol. "Benefits Of Flu Vaccine Substantially Overestimated Says Study." ScienceDaily. ScienceDaily, 21 December 2005. <www.sciencedaily.com/releases/2005/12/051221091232.htm>.
University of Bristol. (2005, December 21). Benefits Of Flu Vaccine Substantially Overestimated Says Study. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2005/12/051221091232.htm
University of Bristol. "Benefits Of Flu Vaccine Substantially Overestimated Says Study." ScienceDaily. www.sciencedaily.com/releases/2005/12/051221091232.htm (accessed July 22, 2014).

Share This




More Health & Medicine News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

TheStreet (July 21, 2014) New research shows Gilead Science's drug Sovaldi helps in curing hepatitis C in those who suffer from HIV. In a medical study, the combination of Gilead's Hep C drug with anti-viral drug Ribavirin cured 76% of HIV-positive patients suffering from the most common hepatitis C strain. Hepatitis C and related complications have been a top cause of death in HIV-positive patients. Typical medication used to treat the disease, including interferon proteins, tended to react badly with HIV drugs. However, Sovaldi's %1,000-a-pill price tag could limit the number of patients able to access the treatment. TheStreet's Keris Lahiff reports from New York. Video provided by TheStreet
Powered by NewsLook.com
$23.6 Billion Awarded To Widow In Smoking Lawsuit

$23.6 Billion Awarded To Widow In Smoking Lawsuit

Newsy (July 20, 2014) Cynthia Robinson claims R.J. Reynolds Tobacco Company hid the health and addiction risks of its products, leading to the death of her husband in 1996. Video provided by Newsy
Powered by NewsLook.com
Tooth Plaque Provides Insight Into Diets Of Ancient People

Tooth Plaque Provides Insight Into Diets Of Ancient People

Newsy (July 19, 2014) Research on plaque from ancient teeth shows that our prehistoric ancestor's had a detailed understanding of plants long before developing agriculture. Video provided by Newsy
Powered by NewsLook.com
Contaminated Water Kills 3 Babies in South African Town

Contaminated Water Kills 3 Babies in South African Town

AFP (July 18, 2014) Contaminated water in South Africa's northwestern town of Bloemhof kills three babies and hospitalises over 500 people. The incident highlights growing fears over water safety in South Africa. Duration: 02:22 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins