Do Vaccine Time Lines Really Matter?

Data revealing that one dose of the Pfizer vaccine is 85% effective - when the global standard for efficacy is 50% - suggests that timelines may not be as important as originally believed. 

The problem is that researchers don't yet know how long any vaccine protection lasts beyond one month so there is understandable hesitation to to recommend changes in the protocol. But as vaccine supplies remain scarce and inoculation continues to be uneven, it may be that rethinking that early guidance about when and how much to give may be adjusted as more information becomes available. JL

Mary Beth Griggs reports in The Verge:

Experts are exploring ways to stretch limited vaccine supplies to get as many people protected as possible, allowing more time in between the first and second doses. Data shows a single dose of Pfizer / BioNTech was 85% effective at reducing symptomatic cases of COVID-19. The CDC has already said that in extreme circumstances, providers can stretch the window between their patients’ shots from three to four weeks up to six.

As the pandemic drags on, experts are exploring ways to stretch still-limited vaccine supplies to get as many people protected as possible. One idea that’s resurfaced this week involves allowing more time in between the first and second doses of the two-dose vaccines. This time, though, there’s some additional data that suggests it might work.

Here’s the idea: two leading vaccines, made by Pfizer / BioNTech and Moderna require two doses. But their early data showed pretty significant protection after the first dose. That got people thinking — is it worth giving more people partial protection with just one dose? Or should they stick to the schedule and fully vaccinate fewer people?

Back in December, some experts encouraged researchers to set up trials to find out if a single dose of a two-dose vaccine would be effective. Around the same time, health authorities in the UK decided to plow ahead without those studies, and prioritized getting first shots in arms, allowing people to delay their doses.

This week, we got more data that shows that a single dose of Pfizer / BioNTech actually does a pretty good job of preventing illness. A study in Israel found that a first shot was 85 percent effective at reducing symptomatic cases of COVID-19 in healthcare workers.

There are some caveats. Here’s a major one: most of the people in the study ended up getting their second dose relatively quickly. That means researchers can only say that the first dose is effective between 15 and 28 days after a person gets that first shot. How long protection lasts beyond that is still unknown.

That’s why some experts are still urging caution when it comes to changing the schedule between those vaccines. “Until such time that there are good clinical trials that show that a single dose provides an equivalent level of protection, I don’t know that we should abandon our approach or create new policies,” Jonathan Tempte told NBC.

It’s messy, and researchers don’t agree. Some, including Anthony Fauci maintain that sticking to two on-schedule doses can help keep the US ahead of dangerous variants of the virus. Others lean towards taking a strategy more like the UK’s.

“THERE’S AN OLD SAYING THAT WE WOULDN’T USE PARACHUTES OR ASPIRIN IF WE WAITED FOR RANDOMIZED TRIALS, EITHER.”

“I think this [strategy] is something on which reasonable people could disagree, but saying you should only do something supported by randomized evidence when there’s an emergency would have precluded us from using masks, social distancing, from doing all the things we know are good public health practices,” Marc Lipsitch, an epidemiologist at Harvard told CIDRAP News earlier this month. He added: “There’s an old saying that we wouldn’t use parachutes or aspirin if we waited for randomized trials, either.”

Here in the US, states are trying to speed up doses — and looking to the federal government for guidance. The CDC has already said that in extreme circumstances, providers can stretch the window between their patients’ shots from three to four weeks up to six. This week, Bloomberg reported that a committee that advises the CDC was considering whether or not to recommend changing the schedule in a smaller working group.

That discussion might not make it to the full committee any time soon. The working group might decide that they need to see more data, or it might not make it to the next COVID-19-related meeting in favor of discussing more pressing issues — including their recommendations for the single-shot Johnson and Johnson vaccine. (Another meeting of that committee is planned for this coming week, but its focus is on a host of other deadly diseases, including ebola, dengue, and rabies.)

Even if the committee doesn’t take it up immediately, the question of when to administer doses is fascinating, and one we’ll be watching as the vaccine rollout accelerates, and more data just keeps pouring in.