JERUSALEM - Pfizer Inc's antiviral treatment Paxlovid reduces Covid-19 hospitalisation and death rates in vaccinated and unvaccinated patients 65 years and older, according to a new study in Israel conducted during the rise of the Omicron variant of the coronavirus.
The treatment, however, was not found to prevent severe illness among younger adults, according to research from Clalit Health Services, Israel's largest healthcare provider.
The use of Pfizer's pills, authorised to treat newly infected, at-risk people in order to prevent severe illness, has soared in the United States along with a spike in infections. Biden administration officials have pushed for the wide use of Paxlovid, which the government purchased and provides free.
Pfizer's clinical trial tested Paxlovid in unvaccinated people who had risk factors for serious diseases and found that the two-drug treatment cut the risk of hospitalisation and death by 90 per cent. That was during the Delta wave of the virus.
There has been some concern, amid anecdotal reports of bounceback covid symptoms after patients get relief from taking Paxlovid, that the treatment might not be as effective in vaccinated patients.
The Israeli study, which was published without peer review as a preprint by the online platform Research Square, included data from nearly 110,000 participants between Jan 9 to March 10, when Omicron was the country's dominant coronavirus variant.
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Senior citizens who had no prior immunity - meaning they were neither vaccinated nor recovered from a previous covid case - saw an 86 per cent drop in hospitalisations with Paxlovid. Those who had prior immunity also benefited, but at a lower rate of 60 per cent.
In total, 0.6 per cent of those 65 and older treated with Paxlovid - or 14 of 2,504 - had to be hospitalised. Those who did not receive Paxlovid were hospitalised about three times more often, or 762 out of 40,315.
In patients ages 40-64, however, regardless of their prior immunity, the data showed no significant benefit in reducing hospitalisation, said Clalit researcher Ronen Arbel.
In reducing mortality, Arbel said the treatment showed a very high benefit in patients 65 and older - an 81 per cent risk reduction. There were no observed benefits in younger adults, who are at less risk of dying from covid.
The researchers noted limitations that may have biased their findings, such as lack of data on the symptoms patients presented, which may have impacted their course of treatment, or patients' degrees of prior immunity.