A basic principle of all communication, not just risk communication, is to segment your audience by the characteristics most relevant to the situation at hand, and then to develop different messages for each audience. The messages can’t be incompatible, of course — but they can and should vary depending on what each particular audience already knows and feels, and on what your goals are with respect to that audience.

Even when talking to a mass audience that cuts across the relevant distinctions, good communicators still do their segmentation thing and address different messages to different groups. “Let me say this to the women of America....” “What’s most important for our allies to bear in mind is....” Doing this in a mass communication has extra advantages, in fact. It not only tells each group what you want them to hear; it also tells everyone else what you think that group needs to hear.

If “shortage” means fewer doses than are medically indicated, the United States has a profound flu vaccine shortage every year. But this year we unexpectedly have fewer doses than people who want them, a supply-versus-demand shortfall. It is generating a lot of communication. At least so far, most of that communication has been extraordinarily deficient in the fundamentals of audience segmentation.

There are other risk communication problems in the way the flu vaccine shortage has been handled: unfounded reassurance, lack of transparency, failure to empathize with people’s emotional reactions, unjustified reports of panic and hysteria, etc. But this column focuses on the audience segmentation problem, and the messages that an audience segmentation approach suggests. We will offer a segmentation scheme for the audience of prospective flu vaccinees — including those that health authorities don’t want to vaccinate this year — on the subject of getting vaccinated.

There are, of course, other audiences for flu vaccine communications: doctors, for example, who are ambivalent about putting public health interests ahead of their patients’ interests; or libertarian policy wonks who are aghast that the United States would resort to expropriation and other draconian, nearly totalitarian measures in response to a less-than-cataclysmic shortfall. And there are other relevant subjects to talk about: good “respiratory etiquette,” for example; or preparedness for a possible pandemic of an entirely new strain of influenza.

But for now, we want to stick to the audience segmentation basics.

Our segmentation is based on two factors. The first factor is the audience’s priority for getting a flu shot this year. It has three values: people targeted for a dose despite this year’s unexpected shortfall; people who would have been targeted for a dose if not for the shortfall; and people who have never been targeted for a dose (although it’s safe for them to get one). The second factor is the audience’s usual behavior. It has two values: people who usually get a shot and people who usually don’t. These two factors make a 3 × 2 matrix, yielding six groups. Tack on children younger than two but older than six months, who are targeted for a vaccine made by Aventis (which is available this year), and you have a total of seven groups to talk to. They add up to everybody in the country, except for a very small eighth group of people for whom a flu vaccination is contraindicated: children under six months and people allergic to something in the vaccine.

Group 1: Targeted for a Vaccine Dose This Year

The first key audience consists of the people that health authorities still want to vaccinate despite the shortage. The biggest components of this group are people aged 65+ and people aged 2–64 with specified chronic illnesses such as asthma, diabetes, and heart disease — people at “high risk” of serious complications and possible death if they get the flu. Pregnant women are included in Group 1, mostly because the flu can complicate their pregnancy. Health care workers are also included, not because they’re at risk themselves if they get the flu but because they are likely to pass it on to their high-risk patients. Finally, the group includes household contacts of children under six months; since the babies are high-risk but too young to be vaccinated, vaccinating their parents gives them the only protection they can get.

(One other group is also targeted, but for different reasons entirely. Soldiers bound for Iraq or other war zones are thought to need a shot so they won’t have to try to fight while they’re sick; they’re high-risk not from the flu but from enemies who can capitalize on the flu. We haven’t seen any numbers on the size of this group. But they have been granted a higher vaccination priority than the medically high-risk target groups. At least so far, there has been very little public discussion of this force protection triage decision. But debate has begun on other groups that might or might not deserve to be targeted for non-medical reasons — Members of Congress, for example.)

Group 1A: Targeted for a shot; usually get one

Size: About 38 million Americans. Included are:

• 24 million people 65 and over (two-thirds of the 36 million in this age range)
• 9 million high-risk people 19–64 (28% of 32 million eligible)
• 680,000 high-risk children 2–18 (out of 6.8 million — only 10%)
• 2.7 million health care workers under 65 (out of 7 million — 38%)
• 500,000 pregnant women (out of 4 million — 12%)
• 1.1 million household contacts of babies under six months (18% of 6.3 million eligible)

Prognosis this year: Despite the shortage, there are more than enough vaccine doses available for everybody in this group to get one ... if nobody else gets one. There are probably enough doses for everybody in this group plus everybody not in this group who has already received a dose ... if nobody else gets one from here on out. There may or may not be enough doses for everybody in this group plus everybody not in this group who has already received a shot plus everybody in Group 1B who is going to want a shot this year for the first time. But even if the redistribution system works perfectly, there are not enough doses for everybody in this group plus everybody in Group 1B.

Thus, many in this group are having to bear the anxiety of worrying whether they’ll get a shot and the hassle of looking for a source, standing in line, etc. And if the demand in Group 1B keeps rising, some — not too many, but some — in this group may end up facing the flu season unwillingly unvaccinated.

Prognosis in future years: No major impact. These are people who usually get their flu shot. Assuming the supply problem is solved before next year’s flu season — a chancy assumption, we realize — Group 1A will be back on their annual schedule in October 2005.

Key messages:
(1) We owe you an apology for policy errors that allowed the shortage to materialize. We owe everyone that apology, but you especially, since your need is high and you have been diligent in the past about meeting it. Your previous practice of getting your flu vaccination contributed to the size of this year’s order for vaccine doses; you certainly had reason to expect that there was, in effect, “a shot with your name on it.”

(2) Even though most of you will in fact get the shot, we cannot guarantee that, though we wish we could. You may need to bear more anxiety and more hassle than usual, and more than you should have to cope with — but in the end you’ll probably get your shot. Hang in there.

(3) It isn’t irrational of you to want to line up, even if some officials are telling you to go home and wait till later in the season. After all, some of you may be left without a shot — and in previous years you’ve always been advised to get vaccinated early. So don’t let anyone call you hysterical or panicky. Lining up in an orderly, patient fashion is understandable and respectable under the circumstances; in fact, it is resourceful and resilient. And it’s good practice for all of us; learning how to manage the lines is an essential preparedness skill for a possible pandemic or a bioterrorist attack. So if you do line up — despite the advice to go home and wait — please bundle up, bring a hot drink in a thermos and a light folding chair if you can, and try to recruit a younger relative or a healthy friend to come with you.

Group 1B: Targeted for a shot; usually don’t get one

Size: About 57 million.

• 12 million people 65 and over (one-third of 36 million)
• 23 million high-risk people 19–64 (72% of 32 million)
• 6.1 million high-risk children 2–18 (90% of 6.8 million)
• 4.3 million health care workers under 65 (62% of 7 million)
• 3.5 million pregnant women (88% of 4 million)
• 5.2 million household contacts of babies under six months (82% of 6.3 million)

Prognosis this year: Some in this group — it’s too soon to tell how many — are going to want flu shots this year ... even though they usually don’t bother. Health officials automatically allow for modest increases in demand, along with population increases, when they guesstimate how many doses they’ll need in the coming year. But the psychology of shortages and the high level of media coverage this year assure a greater-than-usual demand spike.

People in Group 1B who decide they want the shot this year have the same odds of getting it as those in Group 1A, who have wanted it every year. The priority list is based on vulnerability, and vulnerable Johnnies-come-lately have the same priority as the vulnerable diligent. If a 1B person gets a dose instead of a 1A person, that may well be unfair in some sense, and certainly infuriating to the 1A person. But it’s not a public health issue. Mortality and morbidity risk are the same for 1A and 1B. And to the extent that 1B people get doses that would otherwise have gone to people in lower-risk groups, overall mortality and morbidity this year could actually decline.

Prognosis in future years: Here is the biggest public health silver lining of this year’s shortfall: There is a real chance of wooing people out of Group 1B and into Group 1A. Assuming no supply problems in future years, this means that overall demand will go up, the number of high-risk people getting vaccinated will go up, and the annual average of 36,000 flu deaths a year (about 90% of them Group 1 people over 65) will go down.

Key messages:
(1) We wish we had enough vaccine for all of you. You need it, and it’s wonderful that you want it. And it is our fault you may not get it this year. For decades we have tried to warn people about the seriousness of the annual flu season — the need for all high-risk people to get themselves vaccinated and the need to make the vaccine supply more robust and less vulnerable to the kind of shortage we face this year. We failed, and we’re sorry.

(The risk communication frame here: The messenger should always take the blame when the message doesn’t get through. Even if it is arguably more Congress’s fault, or manufacturers’ fault, or capitalism’s fault, or the public’s fault for not heeding your prior warnings, the bottom line is that you failed to persuade all these entities that there were 36,000 deaths a year worth trying to prevent, and that the vaccine production system was precarious.)

(2) The paradox is that our failure to solve the shortage problem may actually help us solve the other problem — the problem of getting everyone in the high-risk groups on board. Tell your doctor, your pharmacist, your family, and your friends that you will definitely want a shot in 2005 ... and every year thereafter. We’ll do everything we can to make sure that shot is there for you.

(3) Obviously there are no guarantees. But there is a very good chance you can get your shot this year too. Thanks to the sacrifice of people in lower-risk groups, we have enough for all the high-risk people who wanted a shot last year. We’re not sure yet if we have enough for all the high-risk people who are going to want one this year. But we want you to want one! Please bear with the anxiety, the lines, the hassle. Please don’t give up. And if you don’t get your shot this year, we hope you will be able to come back next year, and we hope you will still want to, and we hope there won’t be another shortfall!

Group 2: Normally targeted for a dose, but not this year

Because of this year’s shortfall, some people who were previously targeted for the flu vaccine are not being targeted this year. There are two big subgroups in this category.

The first subgroup is healthy people aged 2–64 who live with high-risk people (that is, who live with someone aged 65+ or someone with a chronic health problem). There are a whopping 76 million people in this category. The rationale for targeting them is mostly that the vaccine doesn’t always take. For the elderly in particular, the vaccination failure rate is significant. Vaccinating the household members of high-risk people gives them another layer of protection in case their own vaccination fails. (A secondary rationale is that some high-risk people don’t get vaccinated at all; vaccinating their household members gives them some protection too.) Given this year’s shortage, public health authorities decided they would have to live without this secondary protection. They made a sensible exception for people who live with children younger than six months. These babies are high-risk but too young to be vaccinated themselves, so it’s a priority to vaccinate their parents.

The other large cohort in Group 2 is people aged 50–64 who have no known chronic illnesses that make them high-risk. These folks — there are about 30 million of them, but 10 million of them are also in the first subgroup — weren’t targeted at all until recently, when the Centers for Disease Control and Prevention calculated that roughly a quarter of them have undiagnosed conditions that should put them in the high-risk category. There was no easy way to identify the vulnerable 25%, so everybody in this age range was added to the target list. Now, at least for this year, they’re off again.

Group 2A: Usually targeted but not this year; usually get a shot

Size: Of the 96 million people in Group 2 — healthy housemates of the sick and elderly, and healthy 50–64-year-olds — about 18 million or 19% usually get themselves vaccinated. Divided into the two subgroups, it looks like this:

• 12 million healthy housemates of the sick and elderly (16% of 76 million)
• 6 million healthy 50–64-year-olds who aren’t also in the first subgroup (30% of 20 million)

A side note: The authors are both in Group 2A.

Prognosis this year: Assuming most of the high-risk people who want shots manage to get them, those in Group 2A are the real victims of the shortfall. They have handled their health responsibilities properly in the past. They have contributed to the demand for vaccine, and thus to the supply currently being reallocated to others. Now they have lost their priority, and they probably won’t be able to get a shot, even if they try (and they’re not supposed to try). If there is increased flu mortality and morbidity this year, this is the group that will account for most of it. More people 50–64 with undiagnosed health problems will go unwillingly unvaccinated and get the flu. And more high-risk people who live with unwillingly unvaccinated household members will get the flu. In both cases, an increase in the number of deaths and serious complications is predictable.

Prognosis in future years: No major impact (assuming the vaccine supply rebounds). They’ll be back next year, and presumably there will be a shot for them.

Key messages:
(1) We owe you. You are health heroes (as CDC head Julie Gerberding has said), taking on a real additional risk so more vulnerable people can be protected. Your previous demand contributed to the vaccine supply, and this year will help save the lives of high-risk people. You deserve admiration for your good preventive health habits, and gratitude for allowing the benefits to go elsewhere this year. Certainly you don’t deserve to be stigmatized or castigated.

(2) Here are some things you can do this year to reduce your risk of getting the flu.... These recommendations are always good hygiene, of course, but this year they’re especially important — to protect yourself and the people you live with.

Group 2B: Usually targeted but not this year; usually don’t get a shot

Size: 78 million people, or 81% of the 96 million in Group 2. Subdivided:

• 64 million healthy housemates of the sick and elderly (84% of 76 million)
• 14 million healthy 50–64-year-olds who aren’t also in the first subgroup (70% of 20 million)

Prognosis this year: No major public health impact. Of course people in Group 2B are as likely to suffer flu-related mortality and morbidity as people in Group 2A — but they wouldn’t have been vaccinated in an ordinary year either, so there is no expected increase in their mortality or morbidity.

The psychological situation isn’t quite that simple. Now that they can’t have it, some people in this group will suddenly discover that they want the shot. But their distress probably won’t be as great as for the people in 2A (who are being denied a precaution they usually take) or 1B (who are at greater risk).

Prognosis in future years: If communications are well-handled, this group should be more interested in vaccination in years to come. That is, there is an opportunity to shift people from 2B to 2A. That’s not as important a public health goal as shifting people from 1B to 1A, but it’s not trivial either. There are lives to be saved here too, and habits to be formed for the long term.

Key messages:
(1) We have all had a wakeup call this year: We need a better flu vaccine supply system, and we need to work harder to get the vaccine into the arms of more people. In an ordinary year, you’re a good person to get vaccinated. Let your doctor know you want a flu shot next year; ask to be sent an appointment reminder when the vaccine supplies arrive. We hope to see you next year ... and every year thereafter.

Group 3: Children aged 6 months to 23 months

Children under two haven’t been officially targeted until this year, because public health authorities didn’t have good data on vaccine safety and efficacy. Now they have the data. Children under 6 months shouldn’t be vaccinated; children over six months should. (Yes, the real boundary has got to be fuzzier than that, but arbitrary lines need to be drawn.) The vaccine intended for this group is produced by Aventis, which successfully produced all the vaccine for which it had orders. There’s no known shortfall, though a shortage is still possible if more parents than expected decide to vaccinate their children. (It isn’t entirely clear to us whether doses slated for adults can be used by children instead, nor whether adults can be given the pediatric doses. We have read conflicting reports.)

Size: About six million children, of whom 1.8 million (30%) were vaccinated in 2002, when it was “encouraged” but not yet “recommended.”

Prognosis this year: Probably no major impact. Of course this year’s increased publicity about flu vaccination, added to last year’s much-publicized flu deaths among children, may lead more parents than expected to get their babies and toddlers vaccinated — which is a good thing, except if the demand outstrips the supply and provokes another controversy. We don’t know if this is a likely problem or not.

Prognosis in future years: The furor over the adult flu vaccine supply is — we had to put this somewhere — a shot in the arm for pediatric vaccination. Parents of very young children are a different target audience every year, of course. Still, this new program is off to an unexpectedly good start, thanks to the publicity and the increased demand it will stimulate.

Key messages:
(1) The vaccine for babies and toddlers was not produced by Chiron. There is no manufacturing problem. And we are now very confident that children between 6 and 24 months should be vaccinated — especially in a year when some of the adults around them may not have been. Parents: Call your pediatrician.

(2) Even though all the pediatric doses have been successfully manufactured, there could be a problem if the reallocation program misfires and some of these doses end up elsewhere. And there could be a shortage if the demand unexpectedly increases because of all the publicity.

Group 4: Never targeted for flu vaccination

What’s left are 97 million or so healthy people aged 2–50 who don’t have a relevant chronic disease (as far as they know) and don’t live with or work with a high-risk person. These are the lowest-risk people. That’s not to say they’re unlikely to get the flu. Millions of Group 4 people get the flu every year. They miss somewhere from a few days to a couple of weeks of work or school, in bed and miserable; they may be fatigued and operating below par for weeks more. But nearly all of them recover fully.

Since public health authorities are the ones who set the priority standards, people in Group 4 have the lowest priority for flu shots — even though the economic impact of lost work time due to the flu is far greater than the economic impact of flu-related hospitalization. In principle, public health authorities concede that people in Group 4 should get the shots too; only people allergic to eggs (the medium in which the vaccine is grown) and babies under six months shouldn’t be vaccinated against influenza. But all that’s at stake is wellness and productivity — not mortality and morbidity. So it has never been a priority.

Group 4A: Never targeted for a shot; usually get one

Size: Of the 97 million people who have never been targeted, 15 million or just over 15 % have usually decided to get vaccinated anyway.

It is worth noticing what this means. Presumably, 15 million of the roughly 109 million flu vaccine doses ordered from Chiron, Aventis, and MedImmune for 2004–2005 were the result of previous demand from this group. Of this 109-million-dose order, the Chiron portion, 48 million (44%) was botched. So 56% of the total vaccine order is still available. Okay, then, 56% of the 15 million doses ordered for Group 4A equals 8.4 million doses that Group 4A is being asked — or commanded — to contribute to the medical needs of higher-risk groups.

Prognosis this year: In some ways this is the most interesting group. They have been diligent about pursuing a precaution that public health authorities weren’t especially keen to have them pursue. And now, for the most part, they can’t. Those who manage to finagle a shot anyway will feel the predictable mix of guilt and resentment, the resentment of course exacerbated by the projected guilt. Those who try to get a shot and fail will feel just as guilty and even more resentful. The fact that they have been attacked, ridiculed, and stigmatized by some health authorities and media commentators can only exacerbate both feelings.

And many of those who don’t try to get a shot, who go along with the vaccine rationing policy, must be assumed to have some negative feelings of their own. They have nothing to feel guilty about; in fact, their previous habit of getting vaccinated every year helped build the vaccine supply that is now being redirected to higher-risk people. But they have good grounds for resentment — of the health authorities who let the supply problem go unmanaged, and of the Group 1A and especially the Group 1B people who are getting “their” vaccine doses. They are of course under substantial pressure to pretend to be genial about it all, even to themselves — to try to be nonchalant about the prospect of a week or two flat on their backs. (Employers who ordered the vaccine are under pressure to pretend that they don’t mind either.) The pressure forces the resentment underground, but it’s there and it ought to be addressed.

Prognosis in future years: No major impact. Given our assumption and hope that there will be an adequate vaccine supply from 2005 on, most people in Group 4A will be back in line for their flu shots. Their resentment may fuel an even stronger commitment.

Key messages:
(1) You have a legitimate grievance. Of course you want your vaccine dose, just like every year. Don’t let anybody tell you you’re irrational or selfish to feel angry that others are getting their shots and you can’t.

(2) We are asking you to sacrifice your real stake in your own health for the sake of others whose medical need is greater. In many cases we’re not giving you much choice; we’re commandeering “your” dose for someone needier. We’re sorry, and we’re grateful. Your habit of getting vaccinated is why there are doses available now for us to expropriate, in order to give the vaccine to people according to their need. This should never be forgotten. We owe you.

(3) We haven’t always paid enough attention to the goal of keeping healthy people from an unnecessary bout with the flu. As public health professionals, we’re still focused most on the people whose health is fragile, who might die or require hospitalization. But here’s what we owe you: A vaccine supply robust enough that there’s always a shot “with your name on it” if you want one.

Group 4B: Never targeted for a shot; usually don’t get one

Size: 82 million people, about 85% of the 97 million who have never been targeted.

Prognosis this year: No major health impact, since they’re almost certain to recover if they get the flu. No major economic impact (beyond the usual baseline), since they weren’t planning to get vaccinated anyway. No major psychological impact either. Some may feel a paradoxical attraction to getting vaccinated, now that they can’t. Some may feel confirmed in their disinclination to get vaccinated. Both feelings are likely to be mild.

Prognosis in future years: The public health community has traditionally not cared much whether Group 4 gets vaccinated or not. But for those who worry about things like misery and productivity, 4B is an important swing vote. Some may take away from this year’s vaccination hoopla a sense that they really ought to get a shot too, when the supply gets back to normal. Some may “learn” — or relearn, since it may well be what they thought in the first place — that healthy people don’t need and shouldn’t want flu vaccinations.

Key messages:
(1) It will take at least till next year, but once we get this supply problem straightened out, you should think about getting vaccinated too. Even healthy people have better things to do with their lives than stay home sick.

NOTE: Most of the numbers in this column were extracted from the CDC’s “Interim Estimates of Populations Targeted for Influenza Vaccination from 2002 National Health Interview Survey Data and Estimates for 2004 Based on Influenza Vaccine Shortage Priority Groups,” posted on the CDC website October 11, 2004.