A senior public health official has urged caution as lockdown is lifted, with a warning that a “dangerous wave” of cases is hitting countries “on our doorstep”.

Public Health England’s medical director Yvonne Doyle stressed the importance of following guidance as restrictions are eased.

Meanwhile efforts continued to limit the spread of the South African coronavirus variant following a cluster of cases being discovered in London.

England’s lockdown was partially lifted on Monday, with shops, hairdressers, pavement cafes and pub beer gardens reopening.

Dr Doyle said: “Our efforts over many months have helped to suppress the virus, but I want to stress how even more vital it is to follow guidance as we go back to doing the things we have missed for so long.

“Many countries, including those on our doorstep, are facing another dangerous wave.

“Following guidance continues to be a matter of high protection for us all.

“About half of us do not yet have protective antibodies from either recent infection or vaccination, so when you are offered the vaccine, do not delay.

“It has already saved more than 10,000 lives.”

Dr Doyle’s colleagues were scrambling to contain the outbreak of the South African variant in the capital.

Mutant strains of coronavirus are concerning because they may be less susceptible to current vaccines.

A total of 600 cases of the South African variant have been detected so far in the UK, an increase of 56 in a week.

It is still too early for results on surge testing in response to outbreaks of the South African variant in London and Sandwell in the West Midlands to show up in the figures.

Professor Kevin Fenton, London’s regional director of Public Health England (PHE), said: “As we begin the process of unlocking and re-entering society and mixing, even small numbers of variants, when they occur, can have the potential to spread relatively quickly.”

He told the BBC that was why there was a “proactive programme” of screening and testing for new variants, and “where we have found (them), we surge”.

“We need to get ahead of the infection, and not keep following behind it,” he said.

Additional testing facilities have been set up in parts of London to process hundreds of thousands of residents following the detection of cases of the variant of concern.

Home testing kits were being delivered door-to-door in the N3 postcode area of Barnet, north London after a case was detected locally.

It follows more than half a million adults living in south London boroughs being offered tests, including 264,000 in Lambeth, 265,000 in Wandsworth, and 14,800 in the Rotherhithe ward of Southwark.

The extra testing comes as new analysis revealed that Covid-19 rates dropped below 100 cases per 100,000 people in all local areas of UK for the first time since September.

In other developments:

– Up to April 14 32,444,439 in the UK had received a first dose of vaccine, a rise of 117,835 on the previous day, with 8,513,864 having received both doses, an increase of 343,783.

– A further 30 people were reported to have died within 28 days of testing positive for Covid-19 as of Thursday, bringing the UK total by that measure to 127,191.

– As of 9am on Thursday, there had been a further 2,672 lab-confirmed cases in the UK.

– Scotland’s First Minister Nicola Sturgeon had her first dose of the AstraZeneca vaccine, describing it as an “emotional moment”.

– Northern Ireland’s powersharing executive signed off on a plan for relaxing more lockdown measures in stages on April 23, April 30 and May 24.

Despite the success of the UK’s vaccination programme so far, the rate for staff at older adult care homes is below the level recommended by scientists advising the Government in more than half of England’s local authorities, figures show.

The Scientific Advisory Group for Emergencies (Sage) says 80% of care home staff and 90% of residents need to be vaccinated to provide a minimum level of protection against Covid-19 outbreaks.

Figures published by NHS England on Thursday show that 86 out of 149 local authorities have not reached this threshold for employees.

In 22 areas less than 70% of staff have had a first jab.

Lambeth in south London had the lowest uptake at 50.1%.

The figures came as the Government opened a public consultation on a proposal for staff to be required to get a jab as a condition of deployment to protect elderly residents.

But the Equality and Human Rights Commission warned that “a blanket policy requiring workers to be vaccinated, applied inflexibly, is likely to be unlawful”.

It also raised concerns about so-called vaccine passports, warning that coronavirus status certificates could create a “two-tier society” which discriminates against certain groups.

While the certificates being considered by the Government could be a “proportionate” way of easing lockdown restrictions, the watchdog had concerns about “unlawful discrimination” against people from disadvantaged or ethnic minority backgrounds, by restricting access to jobs and services.