WELLINGTON, Sept 9 (Reuters) - Around a quarter of a million doses of the Pfizer-BioNTech (PFE.N) COVID-19 vaccine bought from Spain will arrive in New Zealand this week, Prime Minister Jacinda Ardern said on Thursday, boosting the country"s inoculation programme. The doses will arrive in Auckland on Friday, Ardern said, adding to some 1.8 million doses being delivered directly from Pfizer throughout September. "This means we don"t have any plans to slow down the rollout," Ardern said at a news conference. Officials have sped up the national vaccination programme as they battle an outbreak of the Delta variant that prompted Ardern to order a snap nationwide lockdown last month. About 1.7 million people in the largest city of Auckland remain in a strict level 4 lockdown but curbs have been eased in the rest of the country. Around 31% of New Zealand"s 5.1 million people have been fully vaccinated, one of the slowest paces among the wealthy nations of the OECD grouping. Officials on Thursday reported 13 new cases of COVID-19, all in Auckland, taking the total number of cases in the latest Delta variant outbreak to 868. Ardern"s lockdowns and international border closure since March 2020 have been credited with reining in COVID-19, largely freeing up day-to-day activities for New Zealanders.