When Donald Trump returned to the White House after a brief spell in hospital with Covid-19 last October he made a video attributing his rapid recovery to a drug he called ‘Regeneron’. ‘They call it a therapeutic drug, but to me it wasn’t therapeutic – it made me better,’ he said. ‘I call that a cure.’
Naturally, given that Trump had on a previous occasion appeared to advocate injecting humans with disinfectant, there was an element of scepticism on the part of many viewers. However, the drug he was talking about went on the receive emergency use authorisation in November from the US Food and Drug Administration. We now have interim results from a Phase 3 trial in which the drug was used as a ‘passive vaccine’.
Regeneron is actually the name of the company; the drug itself is called Regen-Cov. While vaccines like those produced by Pfizer and AstraZeneca work by stimulating the immune system to produce antibodies to the Sars-CoV-2 virus, a passive vaccine delivers ready-made antibodies into the body with the aim of producing an instant, if short-lived, defence against the virus. By contrast, the Pfizer and AstraZeneca vaccines will not confer any immunity until about ten days after the first jab – but thereafter produce a fairly long-term immunity (we still do not know how long) as the body has learnt to recognise the virus. That people are still vulnerable after being vaccinated has been demonstrated in Israel, where many infections have occurred in the initial days after the first jab.
The Phase 3 trial of Regen-Cov, the results of which were published this week, did not attempt to assess the drug’s effectiveness in the situation in which it was administered to Donald Trump – i.e. to someone who is already infected. Rather it was designed to assess how good the drug is at preventing infection in the first place. It involved giving 186 volunteers a subcutaneous injection of the drug and testing them regularly to see if they become infected. A control group of 233 individuals were given a placebo. All participants were tested to check that they had no pre-existing antibodies to the virus.
Of the control group, 23 went on to become infected during the trial, compared with ten of the group given the drug. None of those given the drug, however, went on to develop symptomatic infections – compared with eight of the control group. Those in the placebo group who were infected were found to have a peak viral load 100 times that of the group given the drug. Of those who reported symptoms, 40 per cent in the control group were still suffering from them three to four weeks later; with the group given the drug, symptoms disappeared during the week.
A more comprehensive set of results, from a trial involving 2,000 people, is expected in the spring. If results continue to be positive, an advantage of the drug will be using it as a preventative treatment for people at high risk of infection, such as healthcare workers. It also raises the question: could we be administering the drug along with the active vaccines, so that some vaccinated individuals could be protected as soon as they walk out of the vaccination centre?
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