Beijing, Aug 4 : Chinese authorities are concentrating on students as part of their latest vaccination drive, as the country witnesses its biggest virus surge in months, according to media reports. The government reported 71 new domestic cases on Wednesday -- the highest daily count since January, the BBC said. The latest cases have now spread to at least 16 provinces and municipalities. A vaccination campaign for minors aged 12 to 17 was being expanded to try and combat the spread of the highly contagious Delta variant. Authorities have claimed more than 1.6 billion doses have been administered so far. China's Ministry of Education has asked local authorities to implement a programme targeting vaccinations of school students. Several provinces are already giving school students the jab, but the pressure is on to achieve the government's target of having 80 to 85 per cent of the entire population vaccinated by the end of the year. The latest outbreak started in Nanjiang in the eastern Jiangsu province before spreading to the tourist destination of Zhangjiajie in central Hunan province. From there, tourists carried the virus to at least a dozen cities, including large hubs like Beijing and Chongqing, the media reports said. The city of Yangzhou, which is also in Jiangsu and has a population of more than 4.5 million people, has been put under restrictions after 40 cases were detected. It's thought a 64-year-old woman, who travelled from Nanjiang to Yangzhou and visited popular parlours to play cards, is responsible for the spike in the city. She is now being investigated by police for hiding her travel itinerary from authorities. The Chinese media has reported that some of the people who have tested positive were fully vaccinated, leading to discussion online about the threat of breakthrough infections and whether a booster shot is needed. Officials say vaccines continue to be effective against all the variants so far, and can protect people from severe symptoms and hospitalisations, according to The Global Times. /IANS