NHS Grampian has 2 Covid-19 vaccine studies running from Aberdeen. The one which opened up first has been approved to change into a crossover study.
What is a crossover study?
A crossover study is when the patients taking part receive more than one treatment, but the order is random. So, if there were 2 treatments being tested (treatment A + B) then some patients would receive treatment A first, and others would receive treatment B first.
How did this work in the vaccine trial?
In the Vaccine study, this meant that it asked participants to come back in for 2 more injections. These injections are the opposite from the ones they received at the start of the study. That means that all participants who took part in the crossover study (and received a total of 4 injections since the start of the study) have been vaccinated. Some would have had it at the start of the study (the first 2 injections) and some would have gotten it in the crossover phase (the last 2 injections).
Do the participants know which injections were the vaccines?
The participants are still blinded, which means that they don’t know for sure when they got the vaccine or the placebo. The study staff are also blinded, apart from the members of staff who give the injections. They are not allowed to tell the participants or other staff who was given which injection when. This is done to make sure results are as honest to the truth (or unbiased) as possible.