Monday, November 08, 2010

JID: Epidemiology And Control of Influenza

 

 

# 5036

 

 

The December edition of the Journal of Infectious Diseases (published for the IDSA) contains a couple of interesting offerings (1 study, 1 editorial) on the epidemiology and control of influenza.

 

While vaccination is the best method we have for reducing the incidence of influenza, we know that the way we currently administer vaccines provides less than optimal results.

 

Those over the age of 65, who most years suffer the greatest burden from seasonal flu, are the least likely to mount a robust immune response to the vaccine.  

 

That isn’t to say that there is no benefit to vaccinating the elderly. 

 

The immune response to influenza vaccination no doubt varies from one person to the next, and depends upon a variety of factors including the recipients age and other pre-existing conditions.  

 

 

But as a group, the elderly appear to derive substantially less benefit from vaccination than do those who are younger and have healthier immune systems.  

 

A few past blogs on this phenomenon include:

 

Vaccines: Sometimes You Just Need A Bigger Hammer

Another Study: Flu Vaccines Do Not Reduce Mortality Rates In The Elderly

Study: Flu Vaccines And The Elderly

Flu Shots For The Elderly May Have Limited Benefits

 


All of which leads some researchers to believe that our emphasis on vaccinating the most at risk population – the elderly and those with pre-existing health conditions – may not be the best strategy.

 

Young children, they point out, are basically walking Petri dishes when it comes to respiratory viruses. 

 

They typically shed the virus longer than do adults, are less apt to practice good flu hygiene (covering coughs, sneezes, washing hands, etc.), and since they congregate in schools during flu season, are well positioned to catch – and pass on - whatever is circulating in the community.

 

All of which makes kids terrific spreaders of influenza.

 

They bring it home to their parents and grandparents, who then in turn take it out to the workplace, healthcare facilities, and greater community. 

 

Call it the viral circle of life.

 

Fortunately, as a group children respond pretty well to influenza vaccines – particularly to the LAIV (Live Attenuated Influenza Vaccine).  Which leads many researchers to conclude that the way to control influenza in the greater community is to vaccinate kids.

 

This is an idea that we’ve seen expressed in the past, including:

 

Study: Vaccinating Kids Promotes Herd Immunity
Vax Populi

 

 

Today, we’ve more on this idea.

 

First we’ve the results of a clinical trial, conducted in Texas, on the reduction of community-wide influenza after an aggressive school-based vaccination program in 2007-2008. 

 

Follow the link to read it in its entirety.

 

The Journal of Infectious Diseases 2010;202:1626–1633

© 2010 by the Infectious Diseases Society of America. All rights reserved.

0022-1899/2010/20211-0003$15.00

DOI: 10.1086/657089

MAJOR ARTICLE

Direct and Indirect Effectiveness of Influenza Vaccination Delivered to Children at School Preceding an Epidemic Caused by 3 New Influenza Virus Variants

W. Paul Glezen, Manjusha J. Gaglani, Claudia A. Kozinetz, and Pedro A. Piedra

Abstract (Excerpt)

Results. Almost 48% of children in elementary schools were vaccinated. Significant herd protection attributed to LAIV was detected for all age groups except 12–17‐year‐old students, who were not offered free vaccine. Approximately 2500 medical encounters were prevented at the intervention site. Inactivated vaccine provided marginal protection against the epidemic viruses.

 

Conclusions. LAIV delivered to elementary‐school children before an epidemic caused by 3 new variant influenza viruses generated significant cross‐protection for the recipients and indirect (herd) protection for the community.

 


Basically, researchers compared the results in two Texas communities – one where a school based vaccination program was aggressively mounted, and another (control) community where it was not.   


Even though the uptake of vaccine in the community where the vaccine intervention was mounted was less than 50% - and the vaccine was less than a perfect match - measurable direct benefits to the children and indirect benefits to the community were observed.

 

image

 

 

Were this the only evidence, this would be interesting, but hardly compelling.

 

The accompanying editorial by Edward B. Lewin provides greater context, and provides brief summaries of other studies around the world that have yielded similar results.

 

The editorial, unlike the clinical trial, is a bit easier to digest, particularly for those who are not researchers or clinicians, and is well worth reading in its entirety.

 

The Journal of Infectious Diseases 2010;202:1619–1622

© 2010 by the Infectious Diseases Society of America. All rights reserved.

0022-1899/2010/20211-0001$15.00

DOI: 10.1086/657090

EDITORIAL COMMENTARY

A Paradigm for the Control of Influenza

Edward B. Lewin

Bethesda, Maryland

 

 

The authors of the clinical trial and the editorial combined make a strong argument that free, school- based vaccination programs make for good public health policy.  


That by boosting herd immunity, particularly among school-aged children, we can protect not only them, but the adults they come in contact with that may not be as well protected by the vaccine.

 

Of course, the rub in all of this, is getting enough parents to agree to having their kids get the vaccine every year.  Not necessarily an easy task.

 

But at least, with this study, we have some additional ammunition to back up the recommendation.  

 

 

My thanks to Tetano and Laidback Al on Flutrackers for posting the links to these articles.