The UK government is embroiled in a war of words with the German press, after reports briefed by anonymous government sources emerged in the Handelsblatt, a financial daily, that AstraZeneca’s coronavirus vaccine may be only be 8 per cent effective among over-65s. If true, the vaccine would be close to useless for the elderly, the group most at-risk of Covid-19, and would seriously jeopardise the vaccination strategies of many countries which are relying on AstraZeneca’s cheap and easily transportable jab to provide a large proportion of their immunisation strategy.
But the Handelsblatt story was swiftly denied by AstraZeneca, which called it “completely incorrect” on the record, and later by the German Health Ministry, which clarified that the 8 per cent figure appeared to refer to the proportion of people in the AstraZeneca trials between the ages of 56 and 69, not to the rate of efficacy.
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The problems with this report are twofold. The first is that it emerged as a political story, briefed from political sources (“members of the governing coalition,” as the reporter whose byline led the article put it). The row comes against the backdrop of the rising tensions between the EU and AstraZeneca over the pharmaceutical firm's announcement that it would only be providing the bloc with less than half the doses it has agreed to provide up to March, leading to speculation that one side was attempting to discredit the other during the tense negotiations. Even if not, such speculation is likely to undercut trust at a time when either side can scarcely afford it.
But the virus is not a political story suited to the palace intrigue of political journalism, with its briefings and counter-briefings from anonymous sources. It is a medical story, and data such as the efficacy of a vaccine is not determined by government deliberation. Rather, clinical trials conducted by scientists and verified according to rigorous, transparent criteria determine whether a vaccine is approved by regulators. Muddying the waters by throwing around incendiary claims runs the risk of damaging public trust not just in the AstraZeneca vaccine but in the global vaccine effort as a whole.
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The second issue with the Handelsblatt report is that, colloquially, the term “efficacy” is often misused and misunderstood. A vaccine has two purposes: to prevent serious disease and stop onwards infection, ideally both. But headline efficacy figures aren’t a measure of either of those things. Rather, the figures we hear so much about in the press refer to the proportion of people in a controlled experiment who test positive for Covid-19 after receiving the real vaccine, versus the proportion who test positive after receiving a placebo. The efficacy figure is a measure of risk reduction in a group as a whole, rather than in individualsm, and can even vary from trial to trial.
As the statisticians David Spiegelhalter and Anthony Masters put it: a vaccine having 90 per cent efficacy “does not mean there is a 10 per cent chance of getting Covid-19 if vaccinated – that chance will be massively lower than 10 per cent”.
Yet the way the story was reported led non-experts, understandably, to read “8 per cent efficacy” as “providing 8 per cent protection in individuals”, suggesting that the vaccine was of little use. Again, the potential damage to public trust in vaccinations if their efficacy is downplayed is a serious risk. The fiasco is a warning against treating a medical story as a political one, with echoes far outside Germany’s borders.
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