COVID-19 Vaccine Optimism
Why we need to practice caution while we celebrate milestones in the pandemic
So big news from Pfizer. They are reporting early data showing their vaccine is “more than 90%” effective in preventing COVID-19.
This is huge ! Big news in prevention science and to be quite honest, big news for anyone who is over the pandemic. However, we need to practice cautious optimism and manage our expectations. This is a great step towards finding a solution but we are no where near the end and I will tell you why
Vaccine development is a long, complex process, often lasting 10–15 years that involves a combination of public and private input. Thanks to the brilliant minds and collective global efforts we have been able to accelerate this process exponentially for COVID-19.
“The companies (Pfzier and BioTech) said an early analysis of the results showed that individuals who received two injections of the vaccine three weeks apart experienced more than 90% fewer cases of symptomatic COVID-19 than those who received a placebo.”
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.
Without question, the vaccine will save lives if the 90% efficacy holds up But as this vaccine requires two shots and has to be kept ultra cold, it will take a long time before we can vaccinate enough people for us to be in the safe zone.
Also this is assuming that people won’t be hesitant about getting the vaccine, and there won’t be limited access because of the cold chain requirements..
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).
When the vaccine is highly effective, we need less data to see it. Usually vaccine trials are planned for 150+ total events, this is what we need for a 60% efficacy vaccine.
However the ongoing vaccine trial conducted by Pfizer had just 94 events in the initial analysis and a vaccine efficacy that exceeds 90%. Woah. Amazing.
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!)
While the results are exciting, we will need to independently evaluate them as time goes on.
Unlike treatments, promising data from vaccines do not immediately change standard of care. Until the majority of the population is vaccinated, we will need to continue with the 3 W’s (Wear your masks, wash your hands and watch your distance). In the meantime, The vaccines will undergo a rigorous review process which will play out over time.
What We’ll be looking out for;
- 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)?
This is important because we need to ensure efficacy in high risk groups and we also need to reduce viral shedding (this is when the virus replicates inside your body and then is released into the environment, increasing risk of infection)
So what I’m trying to say is let’s not pop the champagne yet, let’s manage our expectations. We can enjoy the progress and great news whilst being cautiously optimistic.
Having a safe vaccine that we know works is more important (and more effective in the long run) than having a vaccine we think is probably safe and we think kinda works. This takes time to confirm & these trials have only been going on for 3.5 months. We will need many vaccines to meet demand, including vaccines that can be delivered to resource-limited settings.
