Te preliminary results announced yesterday showed that one regimen had an efficacy of 90% when the drug was given as a half dose, followed by a full dose at least one month apart.
A second regimen showed 62% efficacy when given as two full doses at least one month apart. The combined analysis from both dosing regimens showed an average efficacy of 70% .
So they will need a rethink on their dosing amounts. Several independent researchers commented that it's plausible to have different responses due to what's termed as "prime-boost phenomenon," which may be more common among vaccines that use viral vector technology. Hildegund Ertl, a viral immunologist at the Wistar Institute in Philadelphia, says results make sense in the light of some of her work on adenovirus vaccines in mice. She, too, has found that a low first dose can lead to better protection than a higher first dose in a two-dose vaccine. She thinks this is because a lower first dose leads more quickly to the establishment of ‘memory’ immune cells that are triggered by a second-dose boost. Waiting longer between the two doses could achieve the same effect.
Also a similar phenomenon was noted during the tests of a trial vaccine for Ebola where they used the same technique but using a livestock virus.
On the bright side this vaccine is quite stable at standard fridge temperatures for six months and hence storage and distribution is much easier than the the Pfizer or Moderna vaccines. Also the cost is far less compared with other vaccines - being around 3 £. This is because they have a "No Profit" pledge "for the duration of the pandemic."
A second regimen showed 62% efficacy when given as two full doses at least one month apart. The combined analysis from both dosing regimens showed an average efficacy of 70% .
So they will need a rethink on their dosing amounts. Several independent researchers commented that it's plausible to have different responses due to what's termed as "prime-boost phenomenon," which may be more common among vaccines that use viral vector technology. Hildegund Ertl, a viral immunologist at the Wistar Institute in Philadelphia, says results make sense in the light of some of her work on adenovirus vaccines in mice. She, too, has found that a low first dose can lead to better protection than a higher first dose in a two-dose vaccine. She thinks this is because a lower first dose leads more quickly to the establishment of ‘memory’ immune cells that are triggered by a second-dose boost. Waiting longer between the two doses could achieve the same effect.
Also a similar phenomenon was noted during the tests of a trial vaccine for Ebola where they used the same technique but using a livestock virus.
On the bright side this vaccine is quite stable at standard fridge temperatures for six months and hence storage and distribution is much easier than the the Pfizer or Moderna vaccines. Also the cost is far less compared with other vaccines - being around 3 £. This is because they have a "No Profit" pledge "for the duration of the pandemic."
