People are 46% more likely to be reinfected with the Delta variant than the Alpha equivalent, new research has found.
The Covid strain first discovered in India has been spreading rapidly around the country since the start of the summer and currently accounts for around 99% of cases across the UK.
And scientists now believe people can get it again, even if they have already been infected once.
Data from Public Health England (PHE) shows that, while the overall chances of getting reinfected are very low, the Delta variant, first identified in India, poses a higher risk of reinfection.
PHE experts looked at the PCR test results for a group of people who had already had a positive Covid test at least 90 days earlier.
There were 83,197 people who tested positive in the 11-week period of the analysis, of whom 980 (1.2%) had possible reinfections.
The organisation is now conducting further work to understand more about the risk of reinfection.
It came as new figures showed the breakdown of how many people in hospital with the Delta variant have had one or both doses of a Covid-19 vaccine.
From June 21 to July 19, some 1,788 people were admitted to hospital after testing positive for Delta.
Of these, 970 (54%) were unvaccinated, while 530 (30%) had received both doses.
In total, 3,692 people have so far been admitted to hospital with the Delta variant, of whom 2,152 (58%) were unvaccinated and 843 (23%) were fully vaccinated.
From February to mid-July, among the under-50s who had received both vaccines just four patients died with the Delta variant out of 15,346 cases in this group (0.02%).
There have been 34 deaths among the unvaccinated in the same age group, among 119,063 Delta cases (0.02%).
Meanwhile, among the over-50s who have received both vaccinations there have been 220 deaths out of 13,427 cases (1.64%).
And there have been 131 deaths among the unvaccinated over-50s among 2,337 cases (5.6%).
PHE have also designated another variant, known only as B.1.621, as ‘under investigation’ after 16 cases were found in the UK.
Dr Jenny Harries, chief executive of the UK Health Security Agency, said: ‘This most recent hospitalisation data shows once again just how crucial vaccination is in protecting us from severe illness and death.
‘Two doses of vaccine are far more effective against Covid-19 than a single dose, so please make sure that you come forward to get your second dose as soon as you are invited.
‘As we emerge from restrictions and vaccine coverage continues to rise, it is important to remember that, while the protection provided by vaccination is excellent, it is not total.
‘It is still as important as ever that we continue to exercise caution. Remember that meeting outside is safer than inside, get two doses of the vaccine as soon as you can, isolate if you are told to by NHS Test and Trace, and if you show symptoms stay home and get a PCR test.
‘Covid-19 has not gone away and we must all continue to play our part.’
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