Participants who received different vaccines for their first and second doses, regardless of sequence of vaccination, had more side-effects non-serious ones that resolved on their own than those who received the same vaccine twice.
Which vaccine is safest Astra Zeneca.
It found that there was an increased antibody response if the second dose was delayed.
In total, four cases of blood clots have been identified in the same batch of 1 million doses.
For context, this is out of 20.
This is where things get a bit tricky if we actually want to put a figure on precisely how much vaccine efficacy reduces.