IT was a "great day for science and humanity" said Albert Bourla, chairman and chief executive of Pfizer on the day the company announced its Covid vaccine was more than 90 per cent effective at preventing the disease.

It was also a great day for Mr Bourla's bank balance as he cashed in 132,000 Pfizer shares to pocket a $5.6 (£4.2m) million profit.

The value of the company's shares had increased 15% on the day the results were announced - via a press release, rather than a peer-reviewed journal.

The sale was legal and pre-scheduled on August 19, as the company was enrolling late-stage participants, but that doesn't help the optics. Why give anti-vaxxers ammunition?

Likewise the backlash against the Oxford-AstraZeneca vaccine as details trickled out over the past week revealing that the trial arm which had reported 90% efficacy had not included any participants aged under 55 - a detail omitted from its own press release.

Cue speculation online about what else it might be hiding.

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It's easy to rebut the internet's more outlandish myths and misinformation: Covid is a hoax, the virus is spread by 5G towers, the whole pandemic is a nefarious plot orchestrated by Bill Gates to implant us all with microchips.

What's harder to argue is that governments, hospital bosses and pharmaceutical firms do have a checkered history when it comes to patient harm and cover ups.

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Take the infected blood inquiry, which is this month hearing evidence from Scottish haemotologists who were working in the NHS at a time when thousands of patients across the UK contracted HIV and hepatitis C from contaminated blood products.

The scandal in the 1970s and 1980s has long been plagued by claims of institutional cover up and that doctors warned of dangers years before use of the blood products stopped.

Then there is the thalidomide disaster, which saw the drug's German manufacturer ignore warning signs of nerve damage and birth defects (the wife of one of its own employees gave birth to a baby without ears) to embark on a deliberate disinformation campaign stressing the drug's safety. More than 10,000 infants were born with severe deformities.

More recently, the pharmaceutical industry in the US has been condemned for its role in creating a deadly opioid epidemic by compensating physicians to prescribe highly addictive painkillers with false assurances that they were safe for long-term use.

HeraldScotland: Percentages of country populations who say they are confident that vaccines are safe - rates are lowest in parts of EuropePercentages of country populations who say they are confident that vaccines are safe - rates are lowest in parts of Europe

Vaccines are not immune (pardon the pun) to health controversies either.

The 1955 Cutter incident saw 10 children die and hundreds paralysed after they were accidentally given a batch of polio vaccine containing live virus.

In 1976, a swine flu vaccine fast-tracked in a US election year and given to 45 million people caused 30 deaths and 450 cases of Guillain-Barré syndrome, a very serious and occasionally life threatening nerve disorder.

During the 2009/10 H1N1 swine flu pandemic, 1300 of the 30 million people in Europe inoculated with Pandemrix developed narcolepsy, likely to have been caused by the vaccine.

Those who suffer adverse reactions must be acknowledged and compensated.

But countering the anti-vaxxers means being honest about the uncertainties, and putting the risks clearly into context.

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Supposing 45 million people in the UK are given the Covid vaccine and 30 die: there would be outrage.

And yet worldwide to date there have been 64 million known Covid cases and 1.5 million deaths.

Between 1912 and 1922, an average of 6000 measles deaths a year were reported in the US; by 2016 there were 69 deaths.

Vaccines are partly a victim of their own success: the better they are at eradicating a disease, the quicker the population forget its dangers.

Afterall, if millions of people in a population are vaccinated against a potentially deadly disease - so much so that only a few hundred continue to contract it each year - the number of vaccine-related adverse incidents could logically outnumber those caused by the disease itself.

But that doesn't actually make the vaccine more dangerous (and it's worth stressing at this point that serious, let alone fatal, side effects from vaccines are exceptionally rare).

Another problem is that, for vaccines to achieve herd immunity, we need to persuade enough people to be vaccinated - even if the disease poses little risk to them individually.

That could be a particular stumbling block for any vaccine against Covid, which has disproportionately killed the elderly, the disabled, and those with underlying conditions.

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Anything backed by ‘the establishment’ (Government, Big Pharma, the MSM) will provoke knee-jerk suspicion from some, however.

One of the ironies of the MMR-autism scandal is that that same study would have been ripped apart by the conspiracy theorists for its small scale (12 patients), uncontrolled research design, and financial conflicts of interest if conducted by any 'official' body.

The very people most opposed to lockdowns, facemasks, and testing are likely to be those peddling falsehoods about the one thing best placed to release us from it. We have to be ready.

To be successful, a Covid vaccine will need high uptake. Perhaps around 80% uptake.

Misinformation is our biggest enemy now - clear, honest and transparent public health messaging will be more vital than ever to dispel it.