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Three key questions on the Pfizer Covid vaccine

11 November 2020

7:19 PM

11 November 2020

7:19 PM

News that the Pfizer vaccine is 90 per cent effective has sparked a number of questions about the prospect of a vaccine ending this pandemic. As a special adviser in the Department of Health and Social Care until recently, my job was not to be an expert in epidemiology or science. My job was to ask questions, challenge answers, and ensure ministers had the right advice to be able to take important decisions. When it comes to working out how successful a vaccination programme will be, and what they can do to make it as successful as possible, there are three key questions ministers will be considering.

First question: how effective is the vaccine?

Clinical trials consist of enrolling a huge number of participants (43,538 in Pfizer’s case) and splitting them into two groups. One group gets the real vaccine, another gets a placebo. Participants don’t know which group they are in. They are sent away to live their lives, but take regular Covid tests. You then check back a few months later and see how many of each group actually caught Covid-19. If the numbers are equally split between the two groups, then the vaccine had no effect and it doesn’t work. If far more people testing positive come from the placebo group, then that indicates the vaccine has had an effect. Quite how effective the vaccine is considered depends on the weighting of positive cases between the vaccinated and placebo group. In the Pfizer vaccine case, we can be sure that the vast majority of positive cases were in the placebo group, because the efficacy rate has been specified as 90 per cent.

We need to wait until the trial reaches 164 confirmed cases before we have more reliable confirmation – 164 is the number Pfizer agreed with the FDA would constitute a scientifically reliable result. It means that the 90 per cent figure could (and will probably) change, in either direction.

For instance, if more cases emerge among people who have had the vaccine, then the efficacy rate will drop; whereas if the future cases are all from the placebo group, that 90 per cent figure could actually rise. Nonetheless, a 90 per cent efficacy rate from the first 94 positive cases is hugely promising and better than most people expected.

A report from Deutsche Bank pointed out that the market had expected the first data read-out from Pfizer when it hit 32 positive cases, so it’s not just the 90 per cent figure that has caused such cheer. It’s that the trial is far further down the road than has been expected. The big aim of vaccination (for measles, etc) is to provide herd immunity – but this would be harder with a jab that was just 50 per cent effective. But at 90 per cent, the Pfizer vaccine would be up there with other longer long-established vaccines that are proven successes: mumps, polio etc. The below, again, is from Deutsche Bank


That said, it should not only be a case of ‘how effective’ – ‘what effect’ is just as, if not more important, to consider. This virus affects people differently, and it is yet to be seen exactly what effect the Pfizer vaccine has when it comes to preventing severe cases (which are more likely to lead to hospitalisation and death, and therefore healthcare systems coming under pressure). It will be interesting to see the age/risk profile of the 94 cases, and how they split (and in particular what happened to the vaccinated people who still caught the virus.

A vaccine that reduces transmission but not severity is still useful. A vaccine that reduces the likelihood of death/severe illness but doesn’t make the virus less transmissible is extremely useful. Ideally you would want a vaccine to achieve both, of course – but the two are not the same thing, and they have very different policy consequences. Knowing exactly what the vaccine has done to the virus (and who it will be more effective for) is crucial, as it will have a major impact on future policy decisions, especially prioritisation. It explains why government was notably cautious yesterday, and why they will be waiting to see the full data of these trials before basing major policy decisions on their results.

Second question: how long does any protection from a vaccine last for?

Vaccines differ; some offer lifelong protection, some need to be regularly topped up. Immunisations like the flu jab only last six months, which is why you need a new one each year. So how long will the Covid vaccine last for? This is a difficult one for anyone to answer. As with any new vaccine, it takes time to determine the longer-term efficacy. It’s even harder with this virus because it didn’t exist a year ago – so it’s impossible to answer this question with any certainty. We will only learn the answer over time. It’s why many trials will continue to regularly test vaccine participants for a long time to come. If there is suddenly a large spike of positive cases in the vaccinated group of the clinical trials in six months, we will know how long the initial protection lasted for.

This question has particular implications for the roll-out programme. Rolling out the vaccine will require the biggest logistical effort since World War II, not least given the millions that will need to be vaccinated, the requirement to have two doses three weeks apart, and the need for the vaccine to be maintained at temperatures colder than the Arctic. The government has been doing lots of groundwork to get things ready for a working vaccine, but it will still take many months to roll out fully. If this is to be a one-off vaccination programme, the logistical effort will be tough enough. Needing to carry this out repeatedly will be a significant challenge at a policy and also an operational level.

Third question: what will the take-up be?

The interim results suggesting that the Pfizer vaccine has 90 per cent efficacy are, of course, hugely encouraging. Even more so is the fact that the strong results from the Pfizer vaccine increase the probability of success of other Covid-19 candidates that use a ‘spike protein’ approach (like the Oxford-AstraZeneca vaccine). However, we must remember that this 90 per cent figure refers to people who take the vaccine. For an immunisation programme to be fully effective, it will need mass take-up – and that will be more difficult than people appreciate.

Neutralising and countering anti-vaccine propaganda has always been important. It’s now absolutely imperative. Finding the balance between countering misinformation and correcting lies about vaccines, but without giving those claims added oxygen, is incredibly difficult. Indeed, the less airtime such propaganda receives the better and so I won’t say any more about it here. But there is a responsibility for our media and everyone engaged in public debate to behave responsibly, and not amplify views that could have an incredibly damaging impact on both our economic and public health. There has never been a better time to communicate the positive benefits of vaccines than now. Vaccines save lives, and this vaccine will save our society and our economy. We must not let up in making that case.

Even when these three important questions are answered, the government will face a number of thorny political challenges regarding a vaccine rollout. In particular, if we have a working vaccine and there is an end point to this pandemic, what is the risk appetite for reopening the economy before that point? The vaccine will not help us in this second wave and a return to the tiered system on 2 December is inevitable. Different regions would then be hoping to move down towards Tier 1 as we come out of the second wave. The economy has suffered immense damage over the past year, and businesses are desperate to reopen – many will be hoping for an exit from the tiered system completely at some point, especially in the context of positive news about a vaccine. However, ministers will be exceptionally nervous about moving too fast and risking an unnecessary third wave when the end is in sight.

There are also implications for industry and wider society. The prospect of an end point will be a lifeline for many sectors and businesses, but only if they know when that end point actually is. Take my new home, the UK music industry. It often works on long lead times – big events usually need six or nine months to plan and organise and execute. We are not able to spring a festival into existence on a week’s notice. The same is true in many other sectors – for instance, I have friends with weddings in July who are desperate to know if they will be able to have full-scale ceremonies by then.

Government is right to be cautious, and not over promise. But if a vaccine means we could be back to some sort of normality in 2021, we need to know as soon as possible what sort of timeline we should be working towards. This pandemic has been an awful period for our country, and we will all cheer its eventual defeat – but it would be a great tragedy if the summer of 2021 ended up being not just virus-free, but also found itself culturally barren too, simply for lack of preparation time.

Jamie Njoku-Goodwin is chief executive of UK Music, and a former special adviser at the Department for Health and Social Care

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