Since February, the link between infections, hospitalisations and deaths has weakened in people aged 65 and above, while there has been a recent reversal of these trends for those under 65, which likely reflects lower vaccination rates in this group.
However another 178 new coronavirus cases have been confirmed in the past 24 hours. "Data show an increased risk of hospitalisation with Delta compared to Alpha, although PHE's analysis shows that two doses of vaccine gives a high degree of protection against hospitalisation, estimated to be more than 90 per cent", it said.
Health authorities in England, Wales, Scotland and Northern Ireland each run their own vaccination campaigns.
The number of admissions to medical institutions has also been rising, with more than 1,000 people now hospitalised.
The UK government said it needs another four weeks to fully vaccinate more people since unvaccinated people were especially vulnerable, according to a government report.
Speaking at the media briefing on COVID-19, Swaminathan said "We need more data, again from well designed studies on the efficacy of the different vaccines that are in use in different countries against the different variants".
"I certainly think that they ought to, that's definitely our position here, but there is a very big step taken when you move into compulsion".
Public Health England's latest figures show that 928 cases were confirmed county-wide as of Wednesday (June 16th).
The Delta variant is being watched carefully in Alberta, given it is now the dominant strain in the United Kingdom and, with its rapid transmission, is threatening plans there to reopen the economy and lift health restrictions.
The highest prevalence was found in the North West at 0.26 per cent, up from 0.11 per cent in the previous round, while the South West had the lowest at 0.05 per cent, slightly down from 0.07 per cent.