A man walks past a sign at an AstraZeneca site in Macclesfield, central England.Phil Noble | ReutersLONDON — Government ministers and experts in Britain have openly backed a coronavirus vaccine from AstraZeneca and Oxford University, after doubts were raised in the U.S. this week. Housing Minister Robert Jenrick became the latest in a line of people commenting on the vaccine, which has shown to have an average 70% effectiveness at preventing the virus.”I don’t think there is any reason to be unduly concerned,” he told Sky News on Friday morning. “We have now written to the body that will independently assess the veracity and the safety of the vaccine.”The U.K. government’s top scientific advisor, Patrick Vallance, said the focus should be on the fact that the vaccine actually works when asked about doubts regarding the trial.”The headline result is the vaccine works and that’s very exciting,” Vallance said during a news conference on Thursday. Chief Medical Advisor Chris Whitty echoed his comments at the same conference, saying there was always scientific debate about virtually everything. “The key thing from our point of view is to leave this in the hands of the regulator … They will make an assessment with lots of data that is not currently in the public domain on efficacy and on safety,” Whitty added.Rollout next monthBritain has asked its medicine regulator to assess the vaccine for a temporary supply, which could mean it’s rolled out in the country before the end of the year. Four million doses could be used in Britain next month but concerns in the U.S. could mean a rollout there could come much later.The 70% figure came from combining a smaller group of people who received an unintentionally lower dose of the vaccine which produced 90% efficacy, and a larger group who received a higher dosage, showing only 62% effectiveness. U.S. criticismChief of the White House’s Operation Warp Speed, Moncef Slaoui, and others in the U.S. have expressed concern over the age group tested, saying the 90% efficacy was only shown for the lowest risk group, which numbered 2,741 people below the age of 55. John LaMattina, a former president of Pfizer Global R&D, said Tuesday it was “hard to believe” that the FDA would issue an EUA for a vaccine whose optimal dose has only been given to 2,300 people.Pascal Soriot, the CEO of AstraZeneca, confirmed to Bloomberg on Thursday that the British pharmaceutical giant will likely run an additional global trial to evaluate the efficacy of its Covid-19 vaccine.AstraZeneca responseThe company has pushed back against the criticism, emphasizing monitoring of the study by the external Data Safety Monitoring Board (DSMB) and the fact that the data released Monday constituted mere interim results and that more data would follow.It has stressed that the “highest standards” were used and that “additional analysis will be conducted.”This particular vaccine is seen as crucial for emerging markets due to its relative ease of manufacturing and transport, and its low cost compared to potential competitors. AstraZeneca has said its vaccine can be stored, transported and handled at normal refrigerated conditions (36-46 degrees Fahrenheit) for at least six months and administered within existing health-care settings. It has also pledged to distribute the vaccine at no profit “for the duration of the pandemic.”Shares slideShares of AstraZeneca dipped again on Friday and have fallen by nearly 7% since its trial results were released on Monday morning.Jim O’Neill, former chief economist at Goldman Sachs and now the chair of U.K. think tank Chatham House, said he hoped the confusion over the results didn’t “muddy the waters.” He mentioned anti-vaccination activists, a vocal fringe who oppose inoculations. They believe, contrary to scientific evidence, that ingredients in a vaccine can cause harm to the body.”It is a bit confusing in my opinion that presenting these things via press releases without the full detail that the vaccine community kind of wants … is not specially helpful given the sort of general, the sort of anti-vax crowd that are out there,” he told CNBC’s “Squawk Box Europe” Friday.”The second thing is that it does seem … that the regulatory authorities here (in the U.K.) don’t seem to share the same concerns that are being openly expressed in the States.”—CNBC’s Sam Meredith contributed to this article.