© Provided by The iThe Public Health England assessment confirms that the variant is more transmissible than most other strains (Photo: Mercury Press Agency)
The Indian variant could cause a "modest" reduction in the effectiveness of vaccines, the first official assessment of the strain in the UK has concluded.
Analysis by Public Health England says laboratory data shows "modest antigenic change related to some individual mutations in this variant" - suggesting, in theory, the strain could evade immunity created by vaccines.
However this is only based on analysis of the variant, B1617.2, being simulated in a lab as a pseudovirus, and there is, as yet, no evidence that it can escape vaccines among real life cases.
While there is so far only "experimental evidence of functional evasion of vaccine derived immunity", this will nevertheless be of some concern to scientists and ministers as they monitor the threat from this Indian variant to the roadmap out of lockdown.
The assessment confirms that the variant is more transmissible than most other strains, and at least as infectious as the Kent variant B117.
PHE are uncertain over whether this is a genuine biological advantage - with the virus able to attach more easily through its spike protein - or due to large numbers of cases being imported from India, where the variant is endemic, before that country was added to the UK's red list.
If the former is true - that B1617.2 is by nature more infectious - then this will confirm concerns that it could spread more easily and become the dominant strain in the UK.
If it is the latter, this is better news, because while there is already some community transmission in the UK, the number of cases arriving from India will trail off as the red list policy takes effect, and the Kent variant - which is being beaten by the vaccines - will remain the prevalent strain.
The PHE analysis of secondary attack rates - how many people one infected individual passes the virus to - suggests the latter scenario.
Secondary attack rates for B1617.2 are higher than the Kent variant among travellers arriving from India, before the country was red-listed. But the rates are around the same as the Kent variant when cases transmitted within the UK are analysed. This is an encouraging sign.
While officials do not yet know whether the Indian variant is causing worse disease, there are signs that B1617.2 is less fatal: so far four people have died from this strain out of 1255 confirmed cases in England, leading to a case fatality ratio of just 0.3 per cent.
This low figure is likely to be explained by the fact that the most vulnerable to disease and death from Covid-19 have been vaccinated.
But it could also be lower because death rates are a lagging indicator, and the surge in cases will not yet be showing up - if at all - in hospitalisations.
The analysis will underline concerns that ministers acted too slowly to add India to the red list, as it shows a significant proportion of imported cases of the variant in the days up to and immediately after that policy was introduced.