Why having a booster vaccine is like re-watching a film
Dr Sean Elias
From 15th December all adults in the UK will be able to book a third booster jab to help combat the Omicron variant which has been shown to evade vaccine induced immunity. But why are we being asked to get a booster jab with a vaccine that isn’t protecting us? Surely we need a new vaccine? The answer lies in the clever ways in which our immune system works, and in fact, a third dose of the original vaccine may not only protect us against Omicron, but be a better long-term strategy for combating future variants.
It all comes down to how your immune system learns about new diseases. For your immune system seeing a new disease, or a vaccine designed to look a bit like the disease, it is a bit like you or I watching a film for the first time. There are vast amounts on new information for us to take in, including the plot, music, and who’s in the cast… in many ways this information is similar to the active components within a vaccine.
Afterwards, you’ll be able to recall some facts about the film, and I could test your knowledge with a quiz. The ‘quiz’ would determine how well you can recall the film’s details, and is analogous to how your body’s immune system recalls information about a virus from the information given by the vaccine, with a higher ‘score’ meaning a higher level of protective immunity. After watching the film once, you might be able to recall the basic plot, know that ‘the butler did it’, hum the main theme tune, and overall score reasonably well on the quiz.
Now, if you watched the same film a few weeks later, you might start noticing more clues earlier in the film, because you already know the overall plot. When given the same set of questions you can answer the ones you knew before much more quickly and armed with the newly noticed details, get a much higher score in our post-film quiz. This ‘second watch’ is like the second dose of the vaccine, and our immune system works much the same, responding quicker and on a greater scale.
Immune memory, much like our own memory, isn’t perfect. Over time you’ll probably forget some of the finer details of the film, as it isn’t as fresh in your mind, so if I gave you my film quiz six months later your score would probably have dropped. Probably not as low as the quiz you did after you first watched the film, but not quite your best.
Now let’s imagine that sometime later a remake is made of this film — like the CGI version of the original animated Lion King film. It’s basically the same film, but with a few updates, a new song and a slightly different cast.
If you took my quiz about this new ‘variant’ film — having only seen the original film twice 6 months ago — you would still have a good chance of scoring pretty well, and probably score better than someone who has only ever seen this new variant once. If you went back and watched the original again for a third time to boost your knowledge before the quiz on the new variant film you would likely do very well… well bar the questions on Beyonce’s new song and the updated jokes for Timon and Pumba. But in all likelihood, on average you would probably score as well as someone who has never watched the original but has watched the new version a couple of times.
Sometimes when a film is remade (or a virus mutates) the updated ‘variant’ version is a completely new story, like the CGI version of Dumbo compared to the animated original. Now there are some details that cannot be changed which are integral to the identity or plot of the film (Dumbo is an elephant, and… spoiler alert… Dumbo flies). You will easily identify and answer questions based on these details, in the same way our immune system recognises parts of a virus that do not change, what scientists call ‘conserved regions’. Watching the original again will help you remember these details, however these questions only represent a small proportion of the quiz, so you may only realistically ‘max out’ at a pretty low score on my post-film quiz.
To score well you need to watch the new film, in the same way we might need to think about making sure your immune system ‘sees’ a new viral variant, by developing an updated vaccine. Reassuringly, if we follow the same process, your immune system will build up knowledge and you’ll be able to score well in my variant film quiz once more.
At this stage it is worth remembering that films are rebooted all the time, just as new viral variants arise all the time. Some stand the test of time whilst others fade into obscurity. Remember re-makes take time and money and there is no guarantee of success. Film writers often develop early scripts in the same way vaccine designers make early stage vaccines, but production only goes ahead once everyone is convinced it is the right time to do so.
Ultimately though it is often the classic version of a film and its beloved characters that we fall back on, that live long in our memories, bring us joy and allow us to have an opinion about whether newer versions are good or bad. In many ways our immune system is the same. The baseline knowledge provided full stop by vaccination with the original vaccine may prove to be what ultimately what protects us from serious disease, hospitalisation and death even if it isn’t the ‘perfect’ vaccine for the variant that is currently dominating the box office.
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