PORT BLAIR : The Andaman and Nicobar Islands administration has decided to restrict the number of vehicles passing through Jarawa tribal reserve in South Andaman district with immediate effect to prevent the spread of coronavirus among its indigenous population, officials said on Monday.The district administration in Nicobar has made it mandatory for people seeking to enter its islands to produce COVID-19 test certificates, in order to protect the Nicobarese tribal population from the infection, they said.The tribes of the Union territory have low immunity to diseases due to their minimal contact with the outside world.Only one convoy per day has been permitted to ply on the Andaman Trunk Road, which passes through the Jarawa tribal.