Coronavirus vaccines may not protect the elderly, an infectious disease expert has warned.
Dr Natalie Dean said we may need to develop multiple jabs before we can lift lockdown measures.
The 32-year-old added contact tracing and better ventilation should be used to "fill in the gaps" and that Covid-19 deniers will keep their communities at risk.
"So if we find that the vaccine doesn't work as well in older adults then those populations will remain at risk and that's where we are really going to need potentially layering different vaccines which have different attributes to fill in the gaps."
The bio-statistician at the University of Florida also told the podcast: "We have this concept of herd immunity threshold which is how many people need to be vaccinated to be immune in order for new outbreaks from forming.
"Roughly we estimate that's between 50% and 67% - that's a lot of people. Of course there's complications to that and that's just a rough average.
"The way that I think we need to think about it is that the vaccine is one tool and what are other tools? And all of these combined together is what drives our numbers lower.
The expert called for more robust testing, contact tracing and better ventilation to fight the pandemic.
And she added that different discoveries along the way could offer some level of control that will mean the vaccine doesn't need to do a "full lift".
Dr Dean said that the numbers of people who try the vaccine could vary among populations, presenting a further challenge.
She fears that certain sections of communities will still be at risk if they do not choose to engage and says that a lack of public confidence could be behind such a refusal.