LONDON, Oct 21 (Reuters) - The European Union"s drug regulator expects to announce the results of its review of Moderna"s (MRNA.O) COVID-19 booster vaccine next week and also to start a rolling review of Merck"s (MRK.N)antiviral oral pill, a senior official said on Thursday. The results of the Moderna review will be announced on Oct. 25, Marco Cavaleri, head of vaccines strategy for the European Medicines Agency (EMA), told a briefing. Cavalerialso said it was not clear whether Russia would submit an application for its one-dose coronavirus vaccine, known as Sputnik Light, in addition to one already submitted for its two-dose Sputnik V shot. "We don"t have really any clear understanding of whether (the Russian team) intends to submit an application also for this vaccine in the European Union, but we will continue the dialogue to get more clarity on this," he said. The start of a formal review of the two-dose Sputnik V was confirmed in March, but no decision has yet been announced. Reuters reported on Thursday that the regulator was unlikely to decide whether to approve the Russian vaccine until at least the first quarter of 2022 because it still lacked some data required for the review. read more This is in line with what the World Health Organization has said regarding delays in its Emergency Use Listing process. read more BOOSTERS AND PILLS The EMA"s conclusion on boosters of Moderna"s vaccine, Spikevax, is expected for use in people over 12 years of age and the shot is to be given six months after a second dose. The EMA said it expected to receive data on boosters of the single-shot Johnson & Johnson (JNJ.N) vaccine in the coming weeks. On Oct. 4, the watchdog gave the go-ahead for the Pfizer-BioNTech (PFE.N) (22UAy.DE) boosters and recommended a third dose of a shot from Pfizer-BioNTech or Moderna for vulnerable people, leaving it to member states to decide for the rest. read more U.S. authorities have authorised booster doses of Pfizer-BioNTech, Moderna and J&J. While vaccines are the main weapon against COVID-19, Merck"s experimental pill, which it is developing with partner Ridgeback Biotherapeutics, could be a game-changer after studies showed it could halve the chances of dying or being hospitalised for those most at risk of contracting severe illness. read more Britain has already secured a deal for the drug, molnupiravir, well before any approvals.