STACY SQUIRES/StuffThe two cases in Christchurch are from the same household.Two Covid-19 cases have been discovered in Christchurch, including one who could have been infectious in the community for up to a week, Covid-19 Response Minister Chris Hipkins says. The Ministry of Health said it became aware of the two positive cases from the same household in Christchurch on Wednesday evening. One had travelled from Auckland and infected someone they live with. The pair, who are family members, are both unvaccinated. Hipkins said he “couldn’t rule out” a snap lockdown for Christchurch.StuffIn a discussion with Roxie Mohebbi for Stuff’s Whole Truth project, immunologist Dr Maia Brewerton explains why it’s so important for pregnant women to be vaccinated against Covid-19. The local public health unit was gathering information from the cases to identify close contacts and exposure events, including any locations of interest. The ministry is undertaking a public health risk assessment of the situation on Thursday morning and will provide updates after that. READ MORE:* Covid-19 live: Two Covid-19 cases notified in Christchurch* Covid-19: More than 500 Aucklanders are isolating at home The two positive cases were the only people living in their household, Hipkins told RNZ’s Morning Report. The case who travelled from Auckland returned a negative test before catching their flight, he said, before infecting someone they live with. He understood the case had been unwell for a while and could have been infectious in the community for up to a week, he said.ROBERT KITCHIN/StuffCovid-19 Response Minister Chris Hipkins says the initial Covid case may have been infectious in the community for up to a week. (File photo). One other household had been identified as a location of interest. “This is a good reminder to people around the country that cases can pop up and this highlights the importance to get vaccinated.” Hipkins also said the two cases had not been scanning QR codes regularly but were being co-operative with health authorities. He later told Breakfast: “These are both unvaccinated people, both quite unwell as a result of contracting Covid-19.” University of Otago professor of public health Michael Baker told Morning Report it was vital that people with symptoms in Christchurch and the South Island got tested to manage the spread as much as possible. One of the positive cases had recently returned to Christchurch from Auckland, the ministry said.Ross Giblin/StuffInfectious diseases and pandemic expert professor Michael Baker says the wider question is now how many cases are incubating in the South Island (File photo). Pre-travel testing and vaccinations should now become mandatory, Baker said. “If the outbreak is well-defined and it’s just the one case and their household it should be manageable with contract tracing … and no need to move alert levels,” Baker said. “A lot of us would love to see vaccines down to 5 years of age, so children can encounter the virus after they’ve been vaccinated.” A risk assessment from public health was necessary on making any decisions on an alert level change, he said. “The wider question is how many other cases are now incubating in the South Island.” Long-time National MP for Christchurch Gerry Brownlee said the city now faced the possibility of “greater restrictions than we have enjoyed for a long time”. He told RNZ he was never comfortable with the devastation economic and socially that lockdowns brought, but if it was the only way to contain a widespread outbreak it might be necessary. At the end of Tuesday, 89 per cent of about 480,000 eligible people in the Canterbury DHB area had had their first dose of the vaccine – while 68 per cent are fully vaccinated. About 106,000 people from the region still need to have a second jab for 90 per cent of the region to become fully vaccinated.