Cancer patients infected with coronavirus in England are falling seriously ill after being unable to access antibodies or antiviral drugs on the NHS.

Ministers have promised to provide early treatment for 1.3 million people whose immune systems mean they are at higher risk of serious illness, hospitalization or death. Treatments include the monoclonal antibody sotrovimab (Xevudy) and the antiviral drugs nirmatrelvir and ritonavir (Paxlovid), remdesivir (Veklury), and molnupiravir (Lagevrio).

However, the Guardian has been told that while many patients are benefiting from the treatments, others are struggling to access them. Some fell seriously ill as a result. Health charities say red tape and a lack of clear guidelines have led to ‘mass confusion’ and anxiety among some of society’s most vulnerable people.

Kate Keightley, Head of Support Services at Blood Cancer UK, said: “The new treatments are a very important step forward in keeping people with blood cancer safe, and we have heard from many people who had access without problem. But we hear from people who are struggling to access it when they are clearly eligible. While it was understandable that there were teething problems when these treatments were rolled out in January, it is deeply disappointing that there are still significant problems with the system three months later.

“Every day we talk to people with blood cancer who have contracted Covid and who are afraid of what might happen. The last thing they need is the added stress of running to the NHS for treatment and, in many cases, anxiously waiting for a call that doesn’t come.

“We also know of some people who ran out of time to get the treatments and then got seriously ill. Particularly with the infection rate so high, the Government and the NHS need to urgently focus on this to ensure that all eligible people are contacted and can access these treatments.

Phillip Anderson, policy officer at the MS Society, said: “The government has justified its decision to remove 1.3million people – who are at higher risk of severe Covid illness – from all safety measures by saying they still have the lifeline of antivirals. The reality is very different, and we hear of people with MS receiving lateral flow test packs with no explanation of what they are for, while others are unaware that they cannot use a private test to sign up for antivirals now. Failing to communicate these vitally important changes to access them, and believing that their latest batch of hasty advice would suffice, has simply led to mass confusion.

Professor Paul Hunter, from the University of East Anglia, said that given record levels of Covid infection, the government should consider increasing the number of people who are offered antivirals. “Personally, I think anyone over 75 should be given antivirals,” he said. “These are people who are at higher risk of serious illness than younger people, even in the absence of other risk factors.”

NHS England said the treatments were available to all eligible patients and tens of thousands of people had benefited from them. A spokesperson said: “The NHS continues to support GPs, NHS 111 and hospitals to ensure eligible patients can access urgent assessments through Covid-19 Medication Dispensing Units, which allow patients to be treated seven days a week.”

The Department of Health and Social Care said it had obtained more antivirals per capita than any other country in Europe, adding: “Those most at risk of Covid-19, including immunocompromised people , can access antivirals directly and should call NHS 111 or their GP if they have not been contacted by the NHS.