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"These preliminary data indicate that the vaccine is 70.4% effective, with tests on two different dose regimens showing that the vaccine was 90% effective if ad

"These preliminary data indicate that the vaccine is 70.4% effective, with tests on two different dose regimens showing that the vaccine was 90% effective if administered at a half dose and then at a full dose, or 62% effective if administered in two full doses."

skrebbel 6y ago
Does anyone here who understands vaccines know how starting with a smaller does can improve effectiveness? It goes against my intuition.
- BillyTheKing 6y ago
  I wonder what the statistical significance is of those findings. I seems to me that they tried out various different approaches, so the sub-group that received this first-low-second-high treatment might be considerably smaller than the other groups combined leading to slightly less certainty in regards to the findings.
- wbl 6y ago
  This vaccine is a viral vector vaccine. Immunity against the vector can be an issue, but this is moderately informed speculation.
  - ulfw 6y ago
    But it's a chimpanzee vector. Not a human one.
    - freeone3000 6y ago
      Humans can develop an immune response to things that are not infectious to humans.
evandijk70 6y ago
Isn't it more common to determine the dosing regime in Phase I/II trials, and use the Phase III trial as the final test for efficacy?
- garmaine 6y ago
  Phase I/II establishes what a safe dose is. Phase III is when you get the first efficacy data.
- bluGill 6y ago
  It is somewhat common to not be sure what is best after phase I/II and so try two different doses. Though normally you try to avoid that because it is more expensive. In this case Oxford thought the two dose was more promising, but the other had enough promise that they start it too just in case. That the second seems better is a surprise, if they expected this result they would have tested differently. My guess is the lighter dose is really slightly less effective, but the same size is so small that statistical issues make it seem better than it really is.

skrebbel 6y ago

Does anyone here who understands vaccines know how starting with a smaller does can improve effectiveness? It goes against my intuition.

BillyTheKing 6y ago
I wonder what the statistical significance is of those findings. I seems to me that they tried out various different approaches, so the sub-group that received this first-low-second-high treatment might be considerably smaller than the other groups combined leading to slightly less certainty in regards to the findings.
wbl 6y ago
This vaccine is a viral vector vaccine. Immunity against the vector can be an issue, but this is moderately informed speculation.
- ulfw 6y ago
  But it's a chimpanzee vector. Not a human one.
  - freeone3000 6y ago
    Humans can develop an immune response to things that are not infectious to humans.

evandijk70 6y ago

Isn't it more common to determine the dosing regime in Phase I/II trials, and use the Phase III trial as the final test for efficacy?

garmaine 6y ago
Phase I/II establishes what a safe dose is. Phase III is when you get the first efficacy data.
bluGill 6y ago
It is somewhat common to not be sure what is best after phase I/II and so try two different doses. Though normally you try to avoid that because it is more expensive. In this case Oxford thought the two dose was more promising, but the other had enough promise that they start it too just in case. That the second seems better is a surprise, if they expected this result they would have tested differently. My guess is the lighter dose is really slightly less effective, but the same size is so small that statistical issues make it seem better than it really is.