Dr Sara Kayat has issued a warning over suggestions that a vaccine for coronavirus could be available around the festive period.
Last week, it was revealed that a Covid-19 vaccine could be given to the most vulnerable during Christmas.
Kate Bingham, the chairwoman of the UK Vaccine Taskforce, said that there would initially be a "limited supply" of any vaccine that's developed.
Appearing on the programme with Matthew Wright and India Willoughby, Dr Sara reacted to the news that a vaccine could be issued over the next few months.
Speaking to hosts Eamonn Holmes and Ruth Langsford, Dr Sara said: "So Pfizer, as you've mentioned, one of the big drug giants and they've suggested that they've got 100s of thousands ready to roll out for when the trial - or if the trial is a success.
"They are planning on releasing 100million vaccines, 40million of which will be coming to the UK. In addition to Pfizer we know that Jonathan Van Tam, who is the Deputy Chief Medical Officer, is saying that he doesn't think it's unrealistic that we'll be able to have the vaccine from the Oxford trial during December time. So maybe just after Christmas.
"But I think it's really important to be cautiously optimistic because even if we do get a vaccine any time, it won't be available for everybody. It will be for the people most at risk.
"We also need to be aware that it won't be successful in everybody. People will still get the virus despite having the vaccine.
"For example, with the flu vaccine, we know it's only around 50% that are affected, so it could be the same thing. We still need to practice hands, face, space. We'll still need treatment, we'll still need all of these other measures.
"But it will be a cautiously optimistic thing to look forward to."
*This Morning airs weekdays at 10am on ITV
