Russia will conduct a clinical trial of a one-dose "Sputnik-Light" version of its coronavirus vaccine, authorities said on Monday, describing it as a possible "temporary" solution to help countries with high infection rates make it go further.
The slimmed-down vaccine will be tested on 150 people in Moscow and St Petersburg, a government clinical trials register showed.
According to authorities, over a million Russians have so far been inoculated with the original two-dose version of Sputnik V, named after the Soviet-era satellite that triggered the space race in a nod to the project's geopolitical importance for Moscow.
The two-dose vaccine will remain the main version used in Russia, Kirill Dmitriev, the head of Russia's sovereign wealth fund, which is responsible for marketing Sputnik V abroad, said on Monday.
The one-dose version could, however, be used for export.
"'Sputnik-Light' can serve as an effective temporary solution for many countries, which are experiencing a peak of coronavirus infection," Dmitriev, head of the Russian Direct Investment Fund (RDIF), which is covering the costs of the Sputnik-Light trial, said.
Several governments are considering ways to stretch scarce supplies of Covid-19 vaccines, including by delaying second doses and reducing dose sizes.
The aim is to maximise the number of people who have at least partial immunity, thereby potentially reducing the number of severe cases and lessening the burden on healthcare systems.
The two Sputnik doses are delivered using different inactive viruses, known as vectors, and some Russian manufacturers are finding the second less stable to produce, leading to a surplus of the first component.
Last month, Russia shipped 300,000 vials of the Sputnik V vaccine to Argentina, its first major international vaccine delivery. The shipment was made up only of the first component, drawn from this surplus batch, Reuters reported.
President Vladimir Putin has said the single dose will provide less protection than the two doses but "will still reach 85%".
The Gamaleya Institute that developed the vaccine says it is more than 91% effective after the two-dose course.
Gamaleya Institute director Alexander Gintsburg has said that protective immunity after just the first shot of Sputnik V lasts around 3-4 months, the TASS news agency reported.