A Pfizer vaccine is great news, but the small print shows it’s not the silver bullet we would hope

It’s hard not to be excited about the news that Pfizer has developed a vaccine for Covid. So far, the pandemic has felt like a one-sided fight and not in our favour. This announcement gives us all some hope.  

For once, the government even seems to have planned ahead, and has ordered 30 million doses of this new vaccine.

So far, so good. But then the detail starts to emerge. Those 30 million doses, for example, won’t treat 30 million people as the vaccine needs to be given in two doses, so will be sufficient to treat 15 million. Clearly, there will be tough decisions about who will be prioritised and who will be left out. Although it may seem obvious to prioritise some groups such as frontline NHS staff and vulnerable individuals, there are no guarantees at this stage.  

Pfizer says its phase 3 trial data shows the vaccine is 90 per cent effective. Impressive as this is, that still means one in ten won’t be protected. If we know who doesn’t respond to the vaccine in the way we would hope, then we could save 3 million doses and prevent raising false hope for that group. The problem is we don’t know if Pfizer is able to predict who doesn’t respond to the drug. However, the good news is that those from black and minority ethnic communities respond just as well to this new drug.

None of us represent the “average” result so there are likely to be differences in the way individuals respond to this vaccine, even using basic demographic variables such as age or gender. Hopefully Pfizer not only has that data but will make it available but there is no obligation for it to do so – remember, this is a commercial project by a publicly listed company, not an act of charity.

The practical logistics of supplying and distributing this vaccine look about as challenging as you can imagine. The drug needs to be stored at minus 80C. That’s not the kind of facility that many, if any, GP surgeries have. This will also present challenges for the manufacturing of this vaccine at scale. Add to this that we are not the only country competing to secure sufficient doses. It will be critical that we are able to add to the initial order of 30 million doses to ensure the whole population is protected.

This vaccine is given in two doses three weeks apart. Compliance with this will also be challenging, as people forget about follow up appointments or misunderstand about the need for the second dose. The so-called Hawthorn Effect tells us that people behave differently in research trials when they are being observed compared to how they act in real life.

Fortunately, consideration has been given to the workforce needed to distribute this vaccine, and the list of permitted health care workers has been expanded. However, these are not additional new staff: they are drawn from the existing workforce.

We don’t know how long this vaccine provides immunity for. The phase 3 trial was based on immunity at 28 days. Clearly, if it were limited to that time period, it would also have limited utility.

Pfizer recruited over 40,000 people into its trial. That sounds a lot but it’s only when you scale up these vaccines that many of the safety problems emerge – they could be minor but this new vaccine may cause problems that some individuals decide are not worth it. An obvious group is pregnant women, rarely included in such trials, but no less in need of a vaccine.

Undoubtably, it’s time we had some good news in relation to Covid and have at least one weapon in the fight to defeat it. But this won’t be a complete game changer and needs to be viewed alongside all the measures that we’ve become familiar with.  

It is telling that we have developed a vaccine before we have what should be a much less challenging component in our armoury, which is an effective test and trace system.

Ian Hamilton is associate professor of addiction at the University of York