An Epidemiologist on What to Expect From a Covid-19 Vaccine

The study

The study itself is looking at BNT162b2, an mRNA vaccine candidate developed by Pfizer and BioNTech. It is what’s known as a Phase 3 clinical trial, which means that the companies are testing whether the vaccine actually works to prevent disease in a very large group of people — over 40,000 — using a randomized, controlled study design. This sort of study is the gold standard for finding out whether a vaccine works, and what if any side effects we need to be worried about.

Vaccine verisimilitude

The first big, important thing to consider is pretty simple when you think about it: Preventing infections is potentially meaningless in and of itself. Now, cases of Covid-19 are incredibly important, because we know that cases cause hospitalizations and deaths, but the thing is that in this type of research we have to be incredibly careful about our end points. If a vaccine were to prevent infections, but not severe disease or death, it might actually be pretty ineffective as an intervention.

The long road

So that’s the study itself — the results are promising, but we still just don’t have enough information to be sure of the vaccine’s effectiveness in the real world. But that’s not the whole story, because even if the vaccine was 100% effective and we were certain about it’s safety, the pandemic wouldn’t be over tomorrow. People have been treating the idea of having a vaccine as a goal in and of itself, but the reality is that the true end goal is having people immune to the disease, and that’s about more than just creating a vaccine in a lab.

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