Another pandemic flu scare. Is this The Big One, or another false alarm? The US Centers for Disease Control and Prevention (CDC) is so far sounding cautiously optimistic notes on the virulence and pathogenicity of the latest threat, this time out of Mexico.

Public health workers in the US who are old enough to remember the last time that swine influenza virus was thought to have developed the ability to transmit between humans — in 1976 — will shudder at the memory, and will surely be reflecting on the cost of false alarms.

Early in that year, after 13 cases and one death from Swine Flu in army recruits at Fort Dix, NJ, a chain of mostly political events was set in train that led to a decision to attempt to immunise the entire population of the United States. The resulting immunisation campaign succeeded in reaching 45 million people, and might have achieved the goal of 150 million if it had not been abruptly curtailed.

The Swine Flu pandemic never materialised.

What did materialise was an outbreak of Guillain-Barré syndrome caused by the immunisation campaign itself. With a relative risk of 9.2%, a case fatality rate of 5.3%, and an incidence across manufacturers and vaccine lots, this would have been an inordinately risky vaccine at the best of times — far outside the realm of safety we can comfortably rely on with modern vaccines. With the full light of national publicity shining on the program, it was a public relations nightmare.

In the words of current “CyberShrink” Michael A Simpson, writing with the perceptiveness that 13 years of reflection can bring “$135 million (US) was hurriedly spent in order to fail to prevent a nonexistent epidemic of a very minor disease with a campaign which killed well people“.

It was a big blow to the pride — and the credibility — of public health. The embarrassment was compounded by the failure to identify the causative agent of the first recognised Legionnaire’s outbreak which occurred in late summer of the same year.

Considering the closeness of Philadelphia, where Legionnaire’s hit, and New Jersey, where the Fort Dix base is located, and considering the respiratory nature of both illnesses, many Americans conflated the two events.

The Assistant Secretary for Health and the Director of CDC were sacked.

But the decision criteria were sound. Subsequent analyses have confirmed that given the evidence at hand, the time required to formulate, manufacture, and deliver enough vaccine, and the history from 1918 of just how bad things could quickly get, CDC could not in good conscience have advocated anything else.

Lessons were learned that will be of value when The Big One does hit, such as how to develop the logistics of immunisation on a large scale, how to decide who to immunise first, and how to assess adverse reaction potentials.

Hopefully the most valuable lesson of the fiasco will not evade us. That lesson is the importance of keeping politics out of the risk assessment process. The risk management process is necessarily political.