COVID-19 Vaccine Optimism

Photo by CDC on Unsplash

Sounds good, right? So what’s the problem?

Yes, that is a big reduction in symptoms, but it is still not clear that this vaccine is effective at preventing infection altogether. A 90% reduction in symptoms is hugely beneficial to public health, but a different scenario than 90% reduction in new cases.

Let’s take a look at how vaccine trials work

Vaccine trials are “event-driven.” They continue until enough endpoints have accrued (these are lab-confirmed *symptomatic* infections). Statisticians can take planned “early observations” of the data, to tell us if a vaccine is working exceptionally well (or not at all).

So how did Pfizer manage to achieve such results?

Pfizer is currently running a 44,000 patient trial across hotspot areas in the US, Argentina, Brazil & Germany. Pfizer’s first analysis was planned for 32 events, which they pushed back after discussions with FDA. However, by the time they analyzed the data, 94 events had accrued. This shows how quickly trials can generate results when placed in hotspots (and shows us how much transmission is still ongoing!)

Photo by CDC on Unsplash
  • How well does the vaccine prevent severe disease?
  • How well does the vaccine prevent infection?
  • How well does the vaccine work across different subgroups (e.g. the elderly)?



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Rirhandzu Makamu

Rirhandzu Makamu

Postgrad Public Health & Demography 👩🏾‍🎓 | Optimist | “A mind once stretched by a new idea , never returns to its original dimension” — R.W.E.