Sept 23 (Reuters) - The European Medicines Agency (EMA) aims to decide in early October whether to endorse a third dose of the Pfizer-BioNTech (PFE.N), COVID-19 vaccine to be given half a year after the initial two-shot course, saying breakthrough infections added some urgency to its review. "The outcome of this evaluation is expected in early October, unless supplementary information is needed," EMA"s head of vaccines strategy, Marco Cavaleri, told a press briefing on Thursday. Cavaleri"s statement confirmed a Reuters report earlier in the day on EMA"s expected review time on the matter. read more The U.S. Food and Drug Administration on Wednesday authorized a third dose of Pfizer for those aged 65 and older, all people at high risk of severe disease, and others who are regularly exposed to the coronavirus. read more The EU regulator said on Sept. 6 it had begun its evaluation of data submitted by Pfizer and BioNTech for a booster dose to be given six months after the second dose in people 16 years of age and older. read more Moderna (MRNA.O) is also expected to submit data to the EMA this month on its booster dose, an EU document said. EMA added that, in early October at the latest, it would conclude its review of the use of both the Pfizer-BioNTech and the Moderna shots in people with a weak immune system already one month after their initial two-shot regimen. "The evidence is becoming clearer on the need to consider this option for people who may respond poorly to COVID-19 vaccination, such as immunocompromised individuals," said Cavaleri. In an opinion issued in early September and republished by the EMA, the European Centre for Disease Prevention and Control (ECDC) said there was no urgent need to administer booster doses to fully vaccinated people in the general population. But many EU states have already decided to administer a booster dose despite facing higher legal risks without a formal decision to do so by the EMA. read more EMA on Thursday conceded there may be merits in doing so. "With an increase in breakthrough cases that we"ve seen over time, we do understand that member states in Europe and countries elsewhere want to consider now the option of a booster, particularly in vulnerable groups and that is why we have been expediting our review," said Cavaleri. He added he expects Pfizer and BioNTech to submit data on vaccine use in children aged five to 11 years in early October, and similar data from Moderna in early November, with a review likely taking around four weeks if no further data is required. On CureVac"s (5CV.DE) request for vaccine approval, the EMA official said that by the end the year the watchdog should be "in a better position to really understand what could be the next step for this vaccine". CureVac in June and July published disappointing trial data. read more The EU has signed three deals with Pfizer and BioNTech for a total of 2.4 billion doses. The latest contract covers the supply of at least 900 million shots, a large part of which is likely to be needed only if boosters are considered necessary, or if new virus variants emerge against which existing vaccination is not effective. Over 70% of the EU"s adult population has already been fully vaccinated, and the bloc has secured an ample supply of vaccines from several manufacturers. The ECDC has said crucial data on the need and safety of boosters are still missing, in part because it is not yet fully clear how long vaccines protect against the virus.