Question

Metaculus Help: Spread the word

If you like Metaculus, tell your friends! Share this question via Facebook, Twitter, or Reddit.

AstraZeneca vaccine 1.5 dose more effective?

Cross-posted on Metaculus: Pandemics.

Per Statnews

The preliminary results on the AstraZeneca vaccine were based on a total of 131 Covid-19 cases in a study involving 11,363 participants. The findings were perplexing. Two full doses of the vaccine appeared to be only 62% effective at preventing disease, while a half dose, followed by a full dose, was about 90% effective. That latter analysis was conducted on a small subset of the study participants, only 2,741.

...

AstraZeneca plans to explore adding the half dose-full dose regimen to its ongoing clinical trials in discussions with regulatory agencies, a spokesman told STAT in an email.

The half dose was originally administered by accident

Around the time when Astra was initiating its partnership with Oxford at the end of April, university researchers were administering doses to trial participants in Britain.

They soon noticed expected side effects such as fatigue, headaches or arm aches were milder than expected, he said.

“So we went back and checked ... and we found out that they had underpredicted the dose of the vaccine by half,” said Pangalos.

Since the half dose was not part of the originally registered trial, it's more complicated to figure out the significance of the difference here, and the future trials that will specifically test it will presumably be higher powered and able to settle the question more definitively.

Will AstraZeneca's vaccine turn out to be significantly more effective with a half-dose + full dose regimen compared to two full doses?

This question resolves positively if an RCT with over 1000 participants compares a protocol of half dose + full dose to two full doses, and finds that the former is more effective with a p-value below .05.

This question resolves negatively if an RCT with over 1000 participants compares a protocol of half dose + full dose to two full doses, and fails to find a significant difference (i.e. p>.05.)

This question resolves ambiguously if no such RCT is reported by May 1, 2021.

{{qctrl.predictionString()}}

Metaculus help: Predicting

Predictions are the heart of Metaculus. Predicting is how you contribute to the wisdom of the crowd, and how you earn points and build up your personal Metaculus track record.

The basics of predicting are very simple: move the slider to best match the likelihood of the outcome, and click predict. You can predict as often as you want, and you're encouraged to change your mind when new information becomes available.

The displayed score is split into current points and total points. Current points show how much your prediction is worth now, whereas total points show the combined worth of all of your predictions over the lifetime of the question. The scoring details are available on the FAQ.

Note: this question resolved before its original close time. All of your predictions came after the resolution, so you did not gain (or lose) any points for it.

Note: this question resolved before its original close time. You earned points up until the question resolution, but not afterwards.

This question is not yet open for predictions.

Thanks for predicting!

Your prediction has been recorded anonymously.

Want to track your predictions, earn points, and hone your forecasting skills? Create an account today!

Track your predictions
Continue exploring the site

Community Stats

Metaculus help: Community Stats

Use the community stats to get a better sense of the community consensus (or lack thereof) for this question. Sometimes people have wildly different ideas about the likely outcomes, and sometimes people are in close agreement. There are even times when the community seems very certain of uncertainty, like when everyone agrees that event is only 50% likely to happen.

When you make a prediction, check the community stats to see where you land. If your prediction is an outlier, might there be something you're overlooking that others have seen? Or do you have special insight that others are lacking? Either way, it might be a good idea to join the discussion in the comments.