Friday, January 18, 2013

Against Universal Flu Immunization

by Philip Alcabes, Ph.D.

In a strong piece at CNN online yesterday, Jen Christensen points out that no European countries expect the entire population to be immunized against flu — unlike the US, where everyone over the age of 6 months is urged to get flu vaccine every year.

Why does CDC recommend (based on advice by the Advisory Committee on Immunization Practices in 2010) that all Americans — from infancy on up — get immunized against flu?
A few possibilities:

1.  Public health benefit?

No.  Over the past twenty years, flu-vaccine coverage — the proportion of the population that is immunized — has been going up progressively.  But flu hospitalization and mortality rates have been basically constant.  If mass immunization had any public health value, those rates should go down as coverage goes up.

(A technical note: this means that coverage remains below the threshold needed to reduce influenza transmission population-wide, i.e., it isn’t high enough for herd immunity.  But that’s the point.  In order to be of public health benefit, flu vaccine would have to be accepted by almost everybody, every year.  And even that might not be enough:  For a nice explanation of why the efficacy of flu vaccine is limited, see Vincent Racaniello’s blog post.)

2.  Exceptional efficacy of the vaccine?

No.  Based on an observational study of acute respiratory illness patients published this month, the effectiveness of this year’s flu vaccine is 55% against illness caused by influenza type A (which accounts for about 80% of flu cases).  Effectiveness is 70% against type B.  Overall, the chances of being protected against symptomatic flu are less than two out of three.

Jefferson and colleagues found that the overall efficacy of  flu vaccines at reducing influenza A or B infection in children aged 2-16 is only about 65%, and that inactivated vaccines (i.e., the usual injection) had little impact on serious illness or hospitalization from flu-like conditions in this age group.

As with this month’s observational study, Jefferson et al.’s meta-analysis of multiple studies on flu immunization found that the inactivated vaccine had about 73% efficacy at preventing infection in healthy adults — but that efficacy can be as low as about 50% in years when the vaccine isn’t well-matched to the season’s circulating viruses.

Importantly, the Jefferson studies found that effectiveness of immunization — the prevention of serious illness or hospitalization from influenza-like illness — is very low.

There’s no sound public health rationale for encouraging everyone to be immunized against flu every year.

People who are likely to develop serious complications if they are infected can benefit from immunization.  But for most of us, immunization only reduces (by two-thirds) the already rather small chance of infection with influenza.  And it doesn’t protect us much from serious respiratory illness during flu season.

I commented in 2011 on public officials striving to help pharmaceutical companies profit from flu fears. And that’s what we’re seeing again this season — with exaggerated warnings and declarations of flu emergencies. Even though the latest national summary from CDC shows that less than 30% of all influenza-like illness is actually caused by flu this season — and that’s likely an overestimate, since it’s based on testing of more severe cases of acute respiratory illness.  And the surveillance data suggest that the season’s flu outbreak might already be past its peak.

Get immunized against flu if you’re worried.  But keep in mind that vaccination against flu is not going to help the public’s health, and it isn’t highly likely to help yours — it’s primarily your contribution to the profits of Sanofi-Pasteur, Novartis, GSK, or Merck.

Philip Alcabes is a professor in the Adelphi University School of Nursing and director of the Public Health Program. He is an epidemiologist and has studied the history, ethics, and policy of public health.

Friday, January 4, 2013

The Myth of Normal Weight

by Philip Alcabes, Ph.D.

Don’t miss Paul Campos’s commentary on overweight and obesity in today’s NYT.  Responding to the latest report by Katherine Flegal of CDC and coworkers, Campos points out that:

If the government were to redefine normal weight as one that doesn’t increase the risk of death, then about 130 million of the 165 million American adults currently categorized as overweight and obese would be re-categorized as normal weight instead.

The report by Flegal et al., published this week in JAMA, is a meta-analysis of 97 studies on body-mass index (BMI) and mortality.  This new analysis found that mortality risks for the “overweight” (BMI 25-29.9) was 6% lower than that for “normal” BMI (18.5-24.9) individuals.  And those in the “grade 1 obesity” category, with BMIs from 30 to 34.9, were at no higher risk of dying than those in the so-called normal range.   Only those with BMIs of 35 and above were at elevated risk of dying, and then only by 29%.

In other words, people who are overweight or obese generally live longer than those who are in the normal range.  Only extreme obesity is associated with an increased probability of early death.

Flegal and colleagues already demonstrated most of these findings using administrative data, in an article appearing in JAMA in 2005.  There, they reported no excess mortality among people labeled “overweight” by BMI standards, and that about three-quarters of excess mortality among the “obese” was accounted for by those with BMIs above 35.

What’s notable about this week’s publication is that it has attracted the attention of some heavy hitters in the media.  Pam Belluck covered the JAMA report for the NYT.  Although her article seems more interested in propping up the myths about the dangers of fat than in conveying the main points of the new analysis, Belluck does acknowledge that some health professionals would like to see the definition of normal revised.

Dan Childs’s story for ABC News gives a clear picture of the findings, and allows the obesity warriors, like David Katz of Yale and Mitchell Roslin at Lenox Hill, to embarrass themselves — waving the “fat is bad” banner under which they do battle.  MedPage Today gives the storystraight up.   In NPR’s story, another warrior, Walter Willett of Harvard, unabashedly promoting his own persistently fuzzy thinking, calls the Flegal article “rubbish” — but the reporter, Allison Aubrey, is too sharp to buy it from someone so deeply invested.  She ends by suitably questioning the connections of BMI to risk.

Campos’s op-ed piece does the favor of translating the Flegal findings into everyday terms (and without the pointless provisos that burden the NYT’s supposed news story):

This means that average-height women — 5 feet 4 inches — who weigh between 108 and 145 pounds have a higher mortality risk than average-height women who weigh between 146 and 203 pounds. For average-height men — 5 feet 10 inches — those who weigh between 129 and 174 pounds have a higher mortality risk than those who weigh between 175 and 243 pounds.

Is the hysteria about overweight and obesity is over?  I’m sure not.  In today’s article, Campos — who was one of the first to explode the fiction of an obesity epidemic, with his 2002 book The Obesity Myth – reminds us of a crucial fact about public health:

Anyone familiar with history will not be surprised to learn that “facts” have been enlisted before to confirm the legitimacy of a cultural obsession and to advance the economic interests of those who profit from that obsession.

There’s too much at stake with the obesity epidemic for our culture’s power brokers to give it up so quickly.  One day, some other aspect of modernity will emerge to inspire dread (and profits).  In the meantime, we might at least hope to see some re-jiggering of the BMI boogeyman.

Philip Alcabes is a professor in the Adelphi University School of Nursing and director of the Public Health Program. He is an epidemiologist and has studied the history, ethics, and policy of public health.