The New Strain and the Need for Speed

I was going to write a long blog post on the new strain but Zeynep Tufekci has written an excellent piece for The Atlantic. I will quote from it and add a few points.

One of the big virtues of mRNA vaccines is that much like switching a bottling plant from Sprite to 7-Up we could tweak the formula and produce a new vaccine using exactly the same manufacturing plants. Moreover, Marks and Hahn at the FDA have said that the FDA would not require new clinical trials for safety and efficacy just smaller, shorter trials for immune response (similarly we don’t do new large-scale clinical trials for every iteration of the flu vaccine.) Thus, if we needed it, we could modify mRNA vaccines (not other types) for a new variant in say 8-12 weeks. As Zeynep notes, however, the vaccines are very likely to work well for the new variant. It’s nice to know, however, that we do have some flexibility.

The real worry is not that the vaccines won’t work but that we won’t get them into arms fast enough. We were already going too slow but in a race against the new more transmissible variant we are looking like tortoises.

A more transmissible variant of COVID-19 is a potential catastrophe in and of itself. If anything, given the stage in the pandemic we are at, a more transmissible variant is in some ways much more dangerous than a more severe variant. That’s because higher transmissibility subjects us to a more contagious virus spreading with exponential growth, whereas the risk from increased severity would have increased in a linear manner, affecting only those infected.

Here’s a key example from epidemiologist Adam Kucharski:

As an example, suppose current R=1.1, infection fatality risk is 0.8%, generation time is 6 days, and 10k people infected (plausible for many European cities recently). So we’d expect 10000 x 1.1^5 x 0.8% = 129 eventual new fatalities after a month of spread. What happens if fatality risk increases by 50%? By above, we’d expect 10000 x 1.1^5 x (0.8% x 1.5) = 193 new fatalities.

Now suppose transmissibility increases by 50%. By above, we’d expect 10000 x (1.1 x 1.5)^5 x 0.8% = 978 eventual new fatalities after a month of spread.

the key message: an increase in something that grows exponentially (i.e. transmission) can have far more effect than the same proportional increase in something that just scales an outcome (i.e. severity).

I argued that the FDA should have approved the Pfizer vaccine, on a revocable basis, as soon as the data on the safety and efficacy of its vaccine were made available around Nov. 20. But the FDA scheduled it’s meeting of experts for weeks later and didn’t approve until Dec. 11, even as thousands of people were dying daily. We could have been weeks ahead of where we are today. Now the epidemiologists are telling us that weeks are critical. As Zeynep notes holding back second doses looks like a clear mistake and the balance of the evidence also suggests we should move to first doses first:

All this means that the speed of the vaccine rollout is of enormous importance.

…Meanwhile, the United States was reportedly planning to hold back half the vaccine it has in freezers as a hedge against supply-chain issues, and some states may be slowed down by murky prioritization plans. Scott Gottlieb—the former FDA chief and a current board member of Pfizer—has argued that the U.S. should also go ahead with vaccinating as many people as possible right now and trust that the supply chain will be there for the booster. Researchers in Canada—where some provinces decided to vaccinate now as much as possible without holding half in reserve, and will administer the booster with future supplies—estimate that this type of front-loading can help “avert between 34 and 42 per cent more symptomatic coronavirus infections, compared with a strategy of keeping half the shipments in reserve.” (Note that this strategy, which is different from the one the United Kingdom just announced it will adopt in prioritizing the first dose, does not even necessarily involve explicitly changing booster timing protocols in order to maximize vaccination now; it just means not waiting to get shots into arms when the vaccines are currently available.) These were already important conversations to have, but given the threat posed by this new variant, they are even more urgent.

Perhaps most critically, the FDA should approve the AstraZeneca vaccine if not as part of Operation Warp Speed then on a right to try basis. We need every weapon in the arsenal. How many times must we learn not to play with exponential matches?

Addendum: See also this excellent Miles Kimball post, How Perfectionism Has Made the Pandemic Worse.



Add Comment