In Part 1 of this series on adult immunisation I showed that serious respiratory infection in older adults leaves more behind than the diagnosis written on a hospital discharge summary. Some of it resurfaces weeks later as a heart attack. Some of it shows up as a person who never quite gets back to managing on their own.

We already have several vaccines that can prevent some of those infections. The obvious next question is what preventing these infections is “worth.”

The answer may be rather a lot, because much of what an infection takes from an older person has never been measured at all, at least not directly.

New Zealand’s own adult vaccination landscape hints at the problem. Influenza vaccination is funded from age 65. Shingles vaccination is funded at 65, with additional eligibility for some immunocompromised people. Pneumococcal vaccination for adults is funded for specified clinical-risk groups rather than by age. RSV vaccination is recommended for older adults but funded for no one. Four vaccines, four different rules, arrived at separately over roughly two decades. The result isn’t simply a complicated schedule. It’s that the value of preventing illness later in life keeps getting assessed one vaccine and one eligibility group at a time, rather than as a single question.

The TLDR version

Adult vaccination is already good value by conventional accounting. The real question this post asks is whether conventional accounting is missing part of the benefit.

---

The existing economic case is already substantial

Let’s start with the plainest case: seasonal influenza in older adults, the vaccine we have studied longest.

“Cost-effective” sounds like a technical judgement, and it’s really a simple one: does the health gained justify the money spent, once you compare it with what a country is normally willing to pay for a similar amount of health?

When researchers looked across economic studies of influenza vaccination in older adults, the picture was favourable once they counted costs across society — not just hospital care, but also non-medical costs and time lost from work or caring.

The studies that counted only health-system costs were too few and too inconsistent to give a clear pooled answer. In other words, that narrower evidence was uncertain, not negative.

Shingles vaccination tells a similar story. It’s easy to underrate shingles as “just a rash,” but post-herpetic neuralgia is nerve pain that can persist for months or years. Every published US evaluation comparing the modern shingles vaccine against no vaccination has found it worth funding.

Pneumococcal vaccination is more conditional. Newer adult vaccines generally look favourable compared with older pneumococcal vaccines, but the comparison against no adult vaccination at all is less consistent. Part of the reason is that childhood vaccination has already changed which pneumococcal strains circulate in adults, though how much protection it indirectly provides and how long it lasts vary by country and aren’t fixed or guaranteed.

Then there’s the counterexample: RSV.

Three countries evaluated RSV vaccination for older adults at roughly the same time and reached three different conclusions. Canada found it worth funding only for people 70 and older with an existing chronic condition, not for everyone past a certain age. The United States found it poor value for adults in their early sixties — several times over what US decision-makers usually consider acceptable. Germany found it comfortably worth funding for adults from 60. Same vaccine class, same basic biology, three different answers, because the vaccine’s price, the disease it was competing against, and how long its protection lasted all differed between the three analyses. These models mostly value the outcomes directly attributed to RSV. Whether they also capture what an RSV infection triggers beyond RSV itself is a separate question — one we come back to below.

Adult vaccination is too substantial a prevention opportunity to dismiss as economically marginal, but its value is conditional on age, risk, price and how long protection lasts.

---

Widen the lens, and the numbers get bigger

Recently, a series of studies has tried to answer a broader version of the same question: not just whether a single vaccine is worth its cost, but what an entire adult respiratory vaccination programme is worth to society as a whole.

A UK analysis published last year looked at programmes covering pneumococcal disease, RSV, influenza and COVID-19. Depending on how mortality was valued, it estimated first-year benefits of about £5 to £19 for every £1 spent, rising to about £6 to £28 over the lifetime of the vaccinated cohorts. Similar analyses have since appeared for Sweden and Spain. Sweden’s programme returned roughly three times its cost. Spain’s returned somewhere between two and seven times, depending on the same choice that drove the UK’s range.

That range within each country comes down to one specific decision: how a prevented death is valued. One approach assigns the same monetary value to every reduction in mortality risk, regardless of age. Another adjusts the value by how many years of life were actually at stake. Both are established, legitimate methods. In a population that is mostly older, they produce very different totals — because the first treats every prevented death the same, and the second doesn’t.

A preliminary Australian version of the same analysis was presented at a conference this year, though the paper behind it is still under review. For a single year, it put the total societal benefit at around AUD 9.9 billion from reduced mortality risk, AUD 433 million from reduced illness — fewer hospitalisations, hospital beds freed up sooner, fewer outpatient visits — and AUD 67 million from work productivity retained. Add those together and reduced mortality risk accounts for the large majority of the total. That is the same pattern running underneath the UK, Sweden and Spain figures above: when one of these estimates looks large, the reason is usually that most of it comes from placing a dollar value on a statistical reduction in the risk of dying, not from money saved on treatment.

Note that these studies have overlapping authors, a shared modelling framework, work associated with the Office of Health Economics, and, for at least the UK analysis, funding in connection with industry. They are not several independent teams arriving at the same conclusion by different routes. They’re running a consistent methodology, country by country, and getting a consistent directional answer — all positive, but of noticeably different sizes.

Societal value is not the same thing as money saved by the health system, and the UK analysis makes that concrete rather than abstract. Of its £24.2 billion first-year benefit under the VSL approach, only about £0.33 billion is healthcare costs avoided and productivity retained, combined. Nearly all the rest — over £23.9 billion — is the monetised value of reduced mortality risk. That is a real benefit. It is just not one that shows up as cash in a health budget, and the authors say as much themselves: their model does not estimate what, if anything, flows back to government finances, and a separate fiscal analysis would be needed to answer that question directly.

One detail is worth keeping in mind. In Sweden, simply reaching higher vaccination coverage among people already eligible was estimated to raise the total value by 18%. Restricting eligibility cut it by 64%. The vaccine didn’t change in either scenario — only how many eligible people actually got it. Separately, the UK analysis found something related: expanding eligibility increased the total benefit, even as the benefit per pound spent declined slightly. More people benefited; each pound did marginally less work on average. Two different levers, two ways the same headline ratio can move once you look behind it.

Worth remembering

Societal value is not the same thing as money saved by the health system.

---

Even this may still be an underestimate

Here’s where it gets more interesting, and where this post connects back to the last one.

Part 1 established that serious respiratory infection in older adults can trigger consequences well beyond the respiratory system. Hospitalisation for a heart attack runs roughly six times higher in the week after confirmed influenza than it does otherwise. Something like one in five older adults hospitalised with influenza or a similar illness hasn’t recovered their previous level of function months later. Some never get their independence back.

So: if a vaccine prevents some of those infections, and those infections precede some of those outcomes, how much of that prevented harm is actually sitting inside the big benefit-cost numbers above?

A recent review mapped what has actually been studied on the value of adult vaccination across ten countries and four vaccine types. Effects on the health and quality of life of the vaccinated person were well studied. So were deaths prevented and costs avoided by hospitals. Evidence became much thinner for broader effects such as productivity and social equity — and for three specific categories, the review found no evidence at all: effects on the quality of life of the people doing the caring, wider macroeconomic effects, and value to other parts of the health system.

Closer to home, the gap is concrete rather than abstract. A scoping review of everything published on RSV across Australia and New Zealand identified 153 eligible studies. Six of them said anything about economic burden. All six counted direct healthcare costs. None counted what any of it costs a family, or anyone beyond the health system.

You cannot put a value on an outcome you have never measured. This isn’t a complaint about the economists running these models — a model can only combine the inputs it’s given. The problem sits one step earlier. If the true burden of an infection is incompletely measured, then the burden a vaccine prevents is also incompletely measured. And if the preventable burden is incomplete, the estimated value of preventing it will be incomplete as well, no matter how sophisticated the model built on top of it.

Put plainly: the newer, broader studies above are already widening the lens considerably beyond a hospital bill. They may still be missing pieces of what Part 1 described — the months of altered function, the care a family absorbs quietly, the independence that doesn’t come back. Not because anyone overlooked them, but because that evidence mostly doesn’t exist yet, anywhere, in a form a model could use.

---

Where this leaves us

We already know that adult vaccination can prevent substantial illness, and that it often represents good value even under conservative accounting. There is also good reason to think that some of its broader benefits are still missing from current estimates — not because the models are badly built, but because some of what a serious infection takes from an older person has never been properly measured in the first place.

You cannot put a value on an outcome you have never measured.