Vaccines and variants in Bolton

May 17, 2021 • Reading time 3 minutes

The number of confirmed COVID-19 cases in Bolton has increased over the past two weeks to levels last seen in February. The now dominant strain is the B1672 variant, which was first identified in India.

More than case numbers, the big question for both the NHS and the release of lockdown is how effective the vaccine is against this new variant in preventing hospitalisations and death. The very early indications from Bolton give us some suggestion as to what the answer might be – and it’s good news for the vaccine.

As Matt Hancock told us yesterday** 18 people are in hospital in Bolton with COVID. Of these:

  • 12 were not vaccinated (but the majority were eligible)
  • Five had had first vaccination dose
  • One had had both vaccination doses

It might be easy to read this and conclude that the vaccination does not prevent hospitalisation – a 1/3 of the people in the hospital had been vaccinated. However, this ignores the fact that far more eligible people in Bolton have been vaccinated than not – see chart below. And therefore, the proportion of vaccinated people in Bolton who are in hospital is much lower than the proportion of their unvaccinated but eligible neighbours.

If we make our peace with the very small sample and a few simplifying assumptions*** then we can say that the share of people in Bolton in hospital with Covid is currently:

  • about 0.18% for the unvaccinated
  • 0.005% for those who have had a single dose
  • 0.0017% for those that had have two doses

Or, to put it another way: anyone over 50 who has not been vaccinated is up to x100 more likely to end up in the hospital than someone who has had two doses.

Clearly, far more data is needed to understand the precise impact of the vaccine on hospitalisation. But from this small sample, the conclusion is clearly that the vaccine seems to work well at protecting vaccinated people from this new variant – much like it does for the B117 (Kent) variant.

The risk, of course, is that the higher transmissibility of the B1672 variant (India), incomplete vaccination campaign, and removal of lockdown restrictions will mean cases continue to spread and potentially build up in the hospitals.

Just how much protection is offered by the vaccine will determine whether this spread causes sufficient harm to change the course of lockdown easing. In the meantime, it would help to have more granular data on the vaccination programme and all the sequencing that’s happening – it would do a lot to help build up a clearer picture of the risk.


* See table 21 here

** Note that this level of granularity in health data raises information governance concerns, and undoubtedly there is a debate to be had about the greater good

*** specifically that a) all eligible, but unvaccinated, people were aged 50+; b) Royal Bolton Hospital treats people from Bolton CCG only; c) That the “majority” of the 12 unvaccinated people being eligible meant 8 out of the 12. d) That a vaccinated person aged 50+ has the same likelihood of coming into contact with the virus as an unvaccinated person.


Edge Health are a specialist UK healthcare analytics consultancy that use data and insights to improve the delivery of health and care services, so that better outcomes can be delivered more efficiently.