GoKawiilSomething I remember fairly vividly from the first few months of the pandemic was a sense of hopelessness that any effective drug or vaccine would become available anytime soon.
Most people didn’t believe it was possible to develop vaccines in the timeframe needed for them to be useful. Some looked at past vaccine timelines, which had averaged roughly 8 to 12 years, and thought this one would be similar. Others thought that, even though it was an emergency situation, it would still take at least a year and a half, or two years, or maybe even four.
“The grim truth behind this rosy forecast is that a vaccine probably won’t arrive any time soon. Clinical trials almost never succeed. We’ve never released a coronavirus vaccine for humans before. Our record for developing an entirely new vaccine is at least four years.”
— Stuart Thompson, New York Times, April 2020.
I had a different conclusion. In a piece I wrote in the summer of 2020, I explained why I believed that vaccines would most likely arrive within a year of the beginning of the pandemic (placing a 58% probability on enough doses for 25 million Americans being approved and available between October 2020 and March 2021, with my central estimate landing around February 2021).
We now know how the timeline panned out and my forecast was, if anything, slightly too pessimistic, since vaccines first became available three months earlier, in December 2020. In this post, I want to go into more detail and take a look back at what happened. Why were Covid vaccine trials so fast?
The scientific foundation
One of the most surprising things about Covid vaccines is how many of them there are: mRNA vaccines (Pfizer and Moderna), viral vector vaccines (Oxford-AstraZeneca and Johnson & Johnson), protein subunit vaccines (Novavax), inactivated whole virus vaccines (Sinovac and Sinopharm), and others. Although their protection dropped as the virus evolved into new strains, I take this bounty of options as a result of the coronavirus being relatively easy to develop vaccines for.
Part of the reason is the disease itself. With some infections, like HIV, no one clears the virus naturally or develops lasting immunity to it, so it’s hard to know what a vaccine should mimic. Covid-19 was very different: it was evident early on that most people recovered and developed antibodies that could neutralize the virus. This suggested it was possible to prime the immune system with a vaccine.
Another reason was prior research into coronaviruses. Work on SARS and MERS from earlier coronavirus outbreaks meant scientists already understood some of their features. They had identified the key antigen the immune system reacted against – the spike protein – and had animal models and laboratory assays ready to go. Some vaccines against animal coronaviruses had already been developed. Candidate vaccines for the earlier SARS virus had also been developed for humans (and shelved after the 2003 SARS epidemic was contained). When SARS-CoV-2 arrived, lots of this groundwork could be picked up.
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