On Monday 10 May Boris Johnson, the UK prime minister, gave an optimistic appraisal of the state of the UK’s covid pandemic and announced that the next step in easing lockdown restrictions would begin on Monday 17 May.  The 10 May was also the first time in some weeks that the running seven day total reports of covid-19 infections increased over the same period the previous week.  The primary reason for this increase was the rapidly increasing number of cases due to one of the Indian variants B.1.617. It was only four days later that the prime minister held another press conference principally to discuss the rise in this variant and to warn that planned further easing of the lockdown may have to be delayed. 
B.1.617, known colloquially as the Indian variant, was first reported on 1 December 2020, but didn’t start to become common until February 2021.  There are now three subvariants that are recognised B.1.617.1 (the original), B.1.617.2 and B.1.617.3. The original variant was incorrectly called a double mutant as it had two escape mutations L452R and E484Q, though it also had other mutations, most notably P681R, which is also thought to increase infectivity. B.617.1 shows increased resistance to neutralising antibodies from both vaccination and natural covid infection, though not enough to make the vaccine ineffective.  Though this variant will probably reduce vaccine effectiveness somewhat, all vaccines remain effective. B.1.617.1 was first identified in the UK from samples taken on 22 February and reached a peak in mid-April, but now seems to be in decline.
It is the B.1.617.2 variant that is causing most concern in the UK at present. This variant was identified in the UK in samples taken on 18 March and since then estimated numbers have doubled in the UK every 7 to 10 days.  Compared to the earlier variant, B.1.617.2 has lost one of the escape mutations, E484Q. Although no studies or pre-prints have yet been published it is likely that B.1.617.2 will still be effectively controlled by current vaccines even if not quite as effectively as the “Kent” variant B.1.1.7. From leaked emails, The Guardian newspaper reported an outbreak that had affected 15 cases in one London care home a week after residents had received their second dose of the Oxford/AstraZeneca vaccine.  None of these people suffered severe illness. Although anecdotal this outbreak would be consistent with the suggestion that even if vaccine efficacy against infection drops with this new variant, vaccines will still provide substantial protection against severe disease.
On the other hand, B.1.617.2 is somewhat more infectious than B.1.1.7, otherwise it would not be outcompeting this later variant in the UK. The big and unanswered question though is how much more infectious, and will it delay the roadmap out of lockdown? If it is much more infectious then we will struggle to control the spread and some form of continued social distancing measures are likely beyond June, even with high vaccine coverage. If numbers of infections increase substantially then we are still likely to see severe illness and increased hospitalizations and great pressure on the NHS even in people who have been vaccinated. 
Unfortunately, the data do not look good at present. In its most recent technical briefing Public Health England used data on S gene positivity to give more up-to-date estimates of the proportion of all new positives that are likely to be B.1.617.2. In the week ending 5 May, 38.2% of all positive samples were S-gene positive and at least 90% of these would be B.1.617.2.  At the rate of growth in B.1.617.2 over recent weeks and the simultaneous decline in B.1.1.7, the Indian variant is likely to become the dominant variant in the UK sometime in the next few days, if it has not already done so.
During the course of the pandemic in the UK, I do not think we have had such a difficult decision to make as now, because the key evidence that we need to make really informed decisions is still not yet known with certainty. Step 3 in the roadmap out of lockdown has already happened. Even before the emergence of the Indian variants, step 3 was always going to be the biggest jump in reducing control, with indoor meetings now allowed. We now have a very nervous three weeks before we can begin to see the impact of the B.1.617.2 variant on the trajectory of the pandemic. Will we see spread into those age groups and populations where immunization coverage is high? Will the third wave due to this variant mean more hospitalizations and deaths even in those people who have been fully vaccinated?
While it is still not inevitable that step 4 will be delayed until later in the year, this now appears to be the most likely outcome. Whether or not we have to reverse the recent step 3, that so many of us were longing for, should become clear over the next three weeks. With the information we have now, some form of reversal, either at a national, or local level, can’t be ruled out and is looking likely. Critical to preventing further restrictions will be our ability to increase the coverage of current vaccines to all adults.
Paul R Hunter, Professor of Medicine, NIHR Health Protection Research Unit, Norwich Medical School, University of East Anglia, Norwich
Competing interests: PRH is funded by the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Emergency Preparedness and Response at King’s College London in partnership with Public Health England (PHE) and collaboration with the University of East Anglia. The views expressed are those of the author and not necessarily those of the NHS, the NIHR, UEA, the Department of Health, or PHE
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