People who have received both doses of Sputnik V can get any other jab as a booster dose but the best protection is achieved through a combination with Sputnik Light, according to Alexander Gintsburg, the director of the Gamaleya Research Institute of Epidemiology and Microbiology.

"According to various estimates, the efficacy of Sputnik V against the delta strain is 83-90%, which is much higher than that of other vaccines," Gintsburg said, according to TASS.

"Therefore, it'd be good to get a booster dose of Sputnik V after Moderna and Pfizer, and follow Sputnik V with that same Sputnik Light. Other vaccines are possible too, but the effect will be better if Sputnik V is followed by Sputnik Light."

Sputnik Light is the single dose Covid-19 vaccine developed by the Gamaleya Institute, which consists of the first dose of the Sputnik V vaccine.