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1/ Q: What’s going on with the #Oxford/ #AstraZeneca #vaccine & one-dose strategy in Britain?
A: The Oxford/Astrazeneca vaccine was granted emergency authorization & the British government has decided to give as many people a first dose while delaying second doses *up to* 12 wks
A: The Oxford/Astrazeneca vaccine was granted emergency authorization & the British government has decided to give as many people a first dose while delaying second doses *up to* 12 wks
2/ 
What is with this “one dose” strategy?
Basically, bc cases are rising very quickly in the UK & hospitals are under tremendous pressure, there is an urgent need to get #vaccines deployed quickly. http://bit.ly/385hKEj
What is with this “one dose” strategy? Basically, bc cases are rising very quickly in the UK & hospitals are under tremendous pressure, there is an urgent need to get #vaccines deployed quickly. http://bit.ly/385hKEj
3/ The #UK is trialing an approach to get more ppl a first dose as soon as possible, while delaying second doses.
The logic is that increasing the # of ppl given at least partial protection will prevent more hospitalizations/deaths than vaccinating fewer ppl w/two doses.
The logic is that increasing the # of ppl given at least partial protection will prevent more hospitalizations/deaths than vaccinating fewer ppl w/two doses.
4/ This reflects a classic tension btw strategies that may be best for the population vs. individual. While each individual will be better off w/two doses, society may benefit from fewer severe illnesses/deaths if more ppl have partial protection sooner. http://bit.ly/352yL0c
5/ 
Sounds reasonable. What are the downsides?
WANING IMMUNITY. While the trial data look good after one dose, we don’t know the length of that #immunity & immunologists emphasize the second dose is still crucial for full protection.
Sounds reasonable. What are the downsides? WANING IMMUNITY. While the trial data look good after one dose, we don’t know the length of that #immunity & immunologists emphasize the second dose is still crucial for full protection.
6/ Efficacy after the first dose of the #PfizerVaccine (measured from 14 days) was 89%, but the length of that protection is unknown since everyone in the trial got a second dose after three weeks. Similar first dose protection was found for the @moderna_tx mRNA vaccine.
7/ The Oxford/Astrazeneca #vaccine had different lengths of time between doses as part of the trial. 62% of the participants had at least 6 weeks between doses. Protection from severe disease was high after a single dose.
8/ There was evidence that a longer interval between the first & second doses promotes a stronger immune response with the @AstraZeneca vaccine. The regulatory agency (MHRA) thus recommended that the second dose be administered between 4 & 12 weeks after the first dose.
9/ The UK is planning to delay second doses for *both* the @pfizer & Oxford/Astrazeneca vaccines, causing Pfizer to issue a warning that they cannot ensure efficacy if their protocol is changed.
10/ 
VIRAL ADAPTATION. Another concern is that with very high levels of transmission & only partial immune protection, this may be a recipe for the virus to evolve #resistance to the vaccine.
VIRAL ADAPTATION. Another concern is that with very high levels of transmission & only partial immune protection, this may be a recipe for the virus to evolve #resistance to the vaccine.
11/ This could happen if rather than hammering the virus quickly with the full immune response, partial vaccination allows the virus to still replicate in the body even if it prevents severe illness. Mutations from this replication would be more likely to survive & get passed on.
12/ 
BEHAVIOR CHANGE. We’re all super anxious to get back to normal life. Ppl who receive a first dose may feel freer to take more risks, leading to more transmission. Longer gaps btw doses may make it less likely that ppl will return for their second dose.
BEHAVIOR CHANGE. We’re all super anxious to get back to normal life. Ppl who receive a first dose may feel freer to take more risks, leading to more transmission. Longer gaps btw doses may make it less likely that ppl will return for their second dose.
13/ Overall, this strategy is a gamble, as we don’t know for certain the answers to the key questions above. Slower deployment of the two-dose protocol has its own trade-offs. Policymakers are having to make difficult decisions under uncertainty with many, many lives at stake.
14/ These are tough scientific & policy decisions, which the Nerdy Girls are following & discussing intensely amongst themselves. We strive to keep you as up to date on the state of the science as we can. Stay safe &….. Stay tuned! 
