“No way” was my reaction in February 2020 when asked if I’d take the first round of vaccines for COVID-19. The vaccines were still being developed and, as a historian, I knew too much about the problems that accompanied early vaccination attempts. These include a notorious episode in 1955 when Cutter Laboratories released several lots of the newly developed polio vaccine that were faulty despite having passed government safety tests. The contaminated doses led to more than 40,000 children developing some form of the disease.

With stories like that in mind, I was not about to participate in a COVID vaccine beta test.

By February 2021, however, my view had shifted and I eagerly sought my first opportunity to get vaccinated. I was then fascinated by what led to my quick and comfortable COVID-19 about-face, especially because I was researching an episode in US history in which scientists failed to persuade the public about the safety of a nuclear reactor, amplifying rather than lessening fears by treating safety as a technical issue – as a matter of numbers. (I will not be talking about compulsory versus voluntary vaccination programmes, which involve other issues.)

The art of persuasion

All those carrot-and-stick strategies intended to encourage people to get vaccinations – lotteries, musical and sports events, videos of politicians and influencers – would not by themselves have worked on me. In my case it came to make sense to me that I should be vaccinated. I knew to look for help to the Greek philosopher Aristotle, who in his Rhetoric had spelled out three dimensions of how persuasion comes about, for which the Greek terms are ethos, logos, and pathos.

I knew to look for help to the Greek philosopher Aristotle.

Ethos refers to the character or credibility of the speaker or source, logos to the soundness of the argument and pathos to the impact on the hearer. A persuasive scientist speaking to the public, say, needs to establish credibility by citing scientific sources, clearly express what the evidence points to in terms that non-scientists can understand, and engage the audience. Scientists tend to do the first well, sometimes do the second, and can be extremely poor at the third.

Each of these factors played a role in my conversion. At the beginning of 2020 I knew few credible sources about COVID vaccine safety, but by year’s end I had read a growing number of studies about the vaccines by the US Centers for Disease Control and other authoritative institutions – agencies that, I knew, checked and cross-checked their findings.

Second, at the outset I had little idea of how the various COVID vaccines worked, only that they were somehow different from smallpox, measles and polio vaccines. This made me sceptical that a vaccine could be so quickly created. My scepticism was amplified by the knowledge that the US Food and Drug Administration had not “approved” but only “authorized” the COVID vaccines.

But friends of mine with medical training gave me clear and understandable (to me) descriptions of how mRNA vaccines for COVID-19 (the primary two vaccines in use in the US) worked, why they could be created so quickly, and the reasons justifying the unusual approval procedure. These friends explained that, thanks to all the research on SARS – a cousin of COVID – in the first decade of this century, medical researchers already knew much about the disease. It is now possible to produce mRNA segments in laboratories that, when injected into a person, hijack cells to produce the distinctive (but harmless by itself) spike protein and flood the body with it, which in turn sparks production of the antibodies.

The third element in my initial reluctance to get vaccinated was that I felt little urgency when cases in New York State were virtually zero. My feelings of vulnerability mounted quickly after April 2020 as I read more and more about brain fog, ravaged lungs and permanently intubated victims of COVID-19 – and I had friends who suffered and acquaintances who died. All it would take would be a single exposure on a subway, restaurant or close encounter – and that could be me or my family.

All three elements worked together: I had been persuaded by a feeling of vulnerability that was part and parcel of my having been exposed to data and receiving understandable explanations from credible sources. Aristotle had pretty much nailed it.

People’s resistance to vaccination is heightened when they are made to feel guilty or told that they are being irrational.

Except for one aspect. Aristotle was writing about persuading people who shared his background as a citizen of a Greek city-state. I, too, had the same educational background of those who were persuading me – my friends who were health workers, and their positive experiences with the medical establishment. I had been vaccinated as a youth for polio, tetanus, smallpox and other illnesses; I was given a yearly flu shot, by doctors whom I trusted; and I experienced vaccinations as a routine and benign part of my life. Yes I remember the Cutter incident and a number of other vaccine missteps, but integrating these episodes with the rest of what I knew about vaccines made me comfortable with the COVID one.

The critical point

But mine is a privileged experience. Many in my country and abroad rely on inadequate medical treatment from uncaring doctors in poorly equipped hospitals. Others remember trust-undermining unethical clinical trials and experiments on minority populations, or feel manipulated by big pharma or the medical or government establishment, or confront discrimination and structural racism. The resistance of people in these groups is heightened when they are made to feel guilty or told that they are being irrational.

Individuals with those experiences make a different kind of sense out of pushes for vaccines, and are less impressed than I am with more studies, better explanations and warnings of horrible consequences. Just as in the episode I am studying involving public alarm over a nuclear reactor, resistance to vaccination programmes cannot be treated as a purely scientific or technical issue. Persuasion requires more than numbers.