It comes after doctors and NHS trusts said planning for a booster roll out must start now as it will involve bigger challenges.
“We are currently trialling which combinations of jabs are the most effective,” Mr Hancock told BBC Breakfast.
How long will protection from the original double doses last – and will boosters be needed?
Will people get the same vaccine as the original one they got?
How will tweaking the vaccines for new variants work?
Will Covid vaccines be tweaked every year, like the flu vaccine, or will it be more frequently?
Will children be vaccinated and if so, when, where and how, because of the need to get consent?
People have been rushing to get their vaccines in recent days, with more than one million jabs booked on Friday and Saturday in England after vaccinations opened to all over-18s.