The move comes as authorities seek to speed up Russia's vaccination drive that has stagnated while new infections in Moscow and across the country are on the rise.
However, Brazil's health ministry backed down from plans to require all players, coaches and staff to be vaccinated against Covid-19, saying there was not enough time.
Alexander Ginsburg, who heads the Gamaleya Institute that developed Sputnik V, said the spray for children used the same vaccine "only instead of a needle, a nozzle is put on", the TASS news agency reported.
The children's shot is expected to be ready for distribution by Sept. 15, Gintsburg was quoted as saying during a meeting with President Vladimir Putin.
Vietnam is trying to accelerate its vaccine procurement drive to tackle a more stubborn wave of infections, even though its overall case load and fatality numbers remain relatively low.
Vietnam, with a population of around 98 million, has recorded a total of 10,241 coronavirus cases, with 58 deaths, since the pandemic began. Its domestic inoculation started in March.