With every passing day, more Covid immunity is being gained as hundreds of thousands receive the vaccine. Of course, vaccines take time to mature in the body and offer protection, but with roughly a quarter of the population having now received their first inoculation, our approach to dealing with the virus will inevitably need to shift. The big question is how vaccination has changed the equation for how quickly society can be reopened. Modelling from the PCCF project at Bristol University, on cautious assumptions, suggests that the pace of the vaccine rollout would allow significant reopening with herd immunity achieved in July.
First, let’s say how much vaccine immunity has been induced by the vaccine. The latest findings of the PCCF model developed at Bristol University – which is matched against recent ONS antibody survey data – puts the figure today at 44 per cent: 23 per cent coming from recovery from infection, 13 per cent from prior, T-cell immunity, plus a rapidly growing share, already 8 per cent, resulting from the vaccination campaign (see the below chart). So the herd immunity threshold of 70 to 80 per cent is certainly becoming within reach.
When deciding how much freedom to allow, the government should take this into consideration. Over the last 10 days the PCCF has shown, by tracking its Social Distancing Index, that lockdown fatigue may be setting in, with mixing having risen by 25 per cent (see the below chart). Should we be concerned by this? Not at present because the R-rate remains very low (we estimate 0.6, chart three). So infections have been falling (fast) even with more socialisation.
The PCCF model does not simply track how the virus – and society – is behaving. It also offers us projections of what could happen as we reopen society and exit the third lockdown.