Humanity will have to live with the threat of coronavirus “for the foreseeable future” and adapt accordingly because there is no guarantee that a vaccine can be successfully developed, one of the world’s leading experts on the disease has warned.

The stark message was delivered by David Nabarro, professor of global health at Imperial College, London, and an envoy for the World Health Organisation on Covid-19, as the number of UK hospital deaths from the virus passed 15,000.

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A further 888 people were reported on Saturday to have lost their lives – a figure described by communities secretary Robert Jenrick as “extremely sobering” – while the total number who have been infected increased by 5,525 to 114,217.

The latest figures, which do not include deaths in care homes and in the community, put further pressure on the government amid continuing anger among NHS workers and unions over the lack personal protective equipment (PPE) for hospital and care home staff on the front line.

In late March the government’s health advisers said that if UK deaths from Coronavirus could be kept below 20,000 by the end of the pandemic, it would be a “good result” for country. But with an estimated 6,000 people having already died in care homes from Covid-19 – a figure not included in Saturday’s official tally – the 20,000 figure is likely already to have been exceeded.

In an interview with The Observer Nabarro said the public should not assume that a vaccine would definitely be developed soon – and would have to adapt to the ongoing threat.

“You don’t necessarily develop a vaccine that is safe and effective against every virus. Some viruses are very, very difficult when it comes to vaccine development - so for the foreseeable future, we are going to have to find ways to go about our lives with this virus as a constant threat.

“That means isolating those who show signs of the disease and also their contacts. Older people will have to be protected. In addition hospital capacity for dealing with cases will have to be ensured. That is going to be the new normal for us all.”

The comments came as the former UK health secretary Jeremy Hunt said the only way forward was for nations to support a new global health system that would mean far more international cooperation between governments on health issues. It would also require richer nations doing more to support the health systems of the world’s poorest countries.

“I think global health security is going to be on that small but critical list of topics like climate change that we can only solve in partnership with other countries,” Hunt told The Observer.

In a clear criticism of US President Donald Trump who announced last week he was putting on hold funding to the World Health Organisation (WHO) Hunt added: “Surely the lesson of coronavirus is cure not kill…It certainly does not mean cutting their funding (to the WHO).

“One of the big lessons from this will be that when it comes to health systems across the world, we are only as strong as the weakest link in the chain.

“Although China has rightly been criticised for covering up the virus in the early stages the situation would have been whole lot worse if this had started in Africa. International cooperation and supporting health care systems of the poorest countries has to be a top priority in terms of the lessons we need to learn.”

Nabarro’s message is the second grim warning to come from senior ranks of the WHO in the last three days. On Friday, Maria Van Kerkhove, head of WHO’s emerging diseases and zoonosis unit, warned that there was no evidence that antibody tests now being developed would show if a person has immunity or is no longer at risk of becoming reinfected by the Covid-19 virus.

On Saturday it emerged that doctors and nurses treating Covid-19 face shortages of protective full-length gowns for weeks to come, as anger mounts over failures to stockpile them. Gowns were not included in a stockpile list prepared for a potential flu pandemic.

After The Guardian revealed new guidance from Public Health England which instructs healthcare workers to re-use disposable equipment, the GMB, which represents NHS and ambulance staff, said support was “draining away” from Health Secretary, Matt Hancock.

Saffron Cordery, deputy chief executive of NHS Providers which represents many trusts, told the Observer: “We are in a situation where we think this [issue] will last a couple of weeks, which probably does just take us to May. There is a shortage of gowns which is affecting some trusts, but not all. Some have none, and are using the alternatives.”

The government will attempt to gain control of the mounting PPE concerns by appointing Paul Deighton, chief executive of the London Olympics organising committee, to lead efforts to produce equipment in Britain.

Ministers also announced another £1.6bn cash injection to local councils as they attempt to stem a spiralling crisis in social care that is pushing some care providers into the red. Some have been paying inflated prices for commercial protective equipment.