VIENNA, Dec 16 (Reuters) - French-Austrian biotech firm Valneva (VLS.PA) is in talks with a number of countries interested in its COVID-19 vaccine candidate and has the option to boost its production capacity in Scotland, its chief executive told Reuters. The biotech firm has already signed advance purchase agreements for up to 60 million doses with the European Union and a smaller deal with Bahrain. Valneva, which earlier on Thursday said its vaccine was shown to be efficient as a booster following the same shot as an initial vaccination, confirmed it was targeting regulatory approval in the first quarter of next year. Approvals for an initial two-shot course, pursued in parallel in the European Union, Britain and Bahrain, would hopefully pave the way also for green lights for booster use shortly thereafter, CEO Thomas Lingelbach told Reuters TV. "We are in touch with a number of other countries on contracts similar to those that we have already agreed but it"s too early to name those countries," Lingelbach said. Valneva said it has the capacity to produce 100 million doses a year starting in 2022 and could further increase production. Britain, which supplied early financing to Valneva, opted out of its contract for 100 million doses in September and said the vaccine would not be approved for use in the country. Lingelbach said Britain had not revived talks. Active ingredient production on Livingston, Scotland, alone could be increased to 200 million doses per year, contingent on hiring more qualified staff. Filling and packaging are done in Solna, Sweden, while Germany"s IDT Biologika was signed up to help as a contract manufacturer at the end of last month. The shot would be the first inactivated whole-virus vaccine against COVID-19 in Europe, where all of the approved vaccines instruct the human body to produce certain parts of the coronavirus that trigger an immune reaction. Valneva and European health official hope that the shot"s more conventional approach will boost vaccination rates amid qualms in some parts of the population over new vaccine technology currently in use against COVID. Even though the rate of vaccination is rising again somewhat in Europe after levelling off during the summer, Valneva is confident it can play a role in persuading the as-yet unvaccinated. "We hope that with an approval of our vaccine... we can maybe add a few percentage points here and there to the vaccination rates in different countries," said the CEO, who has previously called on the public to seek available shots and not wait for Valneva. Lingelbach added that a trial on patients aged 12-17 years was ongoing and that Valneva planned to begin testing its shot also on children as young as 3 or 5 years old early next year, depending on talks with regulators.