As the country welcomes in 2022, uncertainty remains over how the coronavirus pandemic will unfold.
New Year's Eve celebrations were able to go ahead in England and Prime Minister Boris Johnson said the UK is in an "incomparably better" position than last year.
He insists this in large part down to the "heroic" vaccination efforts that have been made.
But with fears over rising hospitalisation rates due to the Omicron variant, and the waning efficacy of vaccines, there has been increasing debate about whether a fourth jab could, or should, be rolled out.
The move has already been approved in Israel for the most vulnerable.
However, experts are divided on whether continuing booster programmes are the answer to the pandemic in the long-term.
Will Brits be asked to get fourth jab?
On the one hand, data shows that the effectiveness of the current booster jab could wane in as little as ten days.
On the other, research is growing stronger that the Omicron variant is proving to be milder, but more highly infectious, compared with previous strains.
Some modelling suggests the rapid spread of Omicron could cancel out its milder disease leading to thousands of people in hospital and unsustainable pressure on the NHS.
Authorities must now weigh up how to react to these circumstances going forward.
Earlier in December, Health Secretary Sajid Javid confirmed the UK has already signed deals with Pfizer and Moderna for a further 114m extra vaccine doses.
The new deals for 2022 and 2023 include access to modified vaccines if existing jabs are found to be less effective against Omicron.
That would appear to suggest Brits could be offered a fourth dose, given the supply would be more than enough to do so.
Mr Javid said at the time: "Thanks to the Vaccines Taskforce, we have an excellent track record of securing the vaccines the country needs to keep this virus at bay.
"These new deals will future proof the Great British vaccination effort – which has so far delivered more than 115 million first, second and booster jabs across the UK – and will ensure we can protect even more people in the years ahead.
"This is a national mission and our best weapon to deal with this virus and its variants is to get jabs in arms – so when you are called forward, get the jab and get boosted."
But are boosters the answer?
However, some experts worry that rich countries like the UK are in danger of 'over-vaccinating' their populations and that it may not be necessary - at least for those at low risk from coronavirus.
There are many variables to consider.
As we approach two years since Covid-19 first began its spread across the globe, the vast majority of the UK population has either been infected with the virus, or been vaccinated, or both.
Experts agree that the body's immune system produces a more complete response to infection compared with vaccination - although jabs have proven to be extremely effective in stopping severe illness.
And in fact, it appears the most effective protection is to have been infected and then get a vaccination.
One study by academics at Birmingham University found that the antibody response to vaccination in care home residents who had previously contracted Covid, was eight times higher than those who had not.
Some experts argue that each time a person is exposed to a virus like Covid-19, they should build up a better immune response.
Prof Adam Finn, a government adviser on vaccines, told the BBC: "This isn't proven, but it could be a lot cheaper and simpler to let that happen than spend the whole time immunising people."
We could end up "locked into a cycle of boosting" without seeing if it was necessary, he added.
'Natural vaccine'
Professor Ian Jones, a virologist at the University of Reading, told MailOnline: "The vaccine response clearly wanes but it is not clear if the boosted response will wane in the same way or at the same rate.
"Boosting every 10 weeks or every time a new variant appears to be on the rise is not doable and in consequence I think we need some sort of grading system for new variants to ensure we act appropriately and practically."
Top-up jabs for the vulnerable ahead of each winter is already the strategy we use to tackle similar viruses, such as the flu.
Professor Jones said whether all adults would need it depends on how the Omicron situation plays out.
"If Omicron is an attenuated strain already on its way to endemicity then later versions may be even more mild and the need for vaccination for an otherwise fit adult might recede, " he added.
"You have to remember that making you very sick is no good to the virus at all, all it 'wants' is to transmit, so virus evolution will tend towards a less severe strain which you will pass around as you will struggle on with work etc much as we do for common colds."
However, Prof Jones warned against any 'chickenpox' style parties where people intentionally try to catch Omicron, saying we needed to protect people who could get severely ill from the virus.
'Covid will effectively become another cause of common cold'
As the UK and the wider world looks into its third year coping with coronavirus, experts offer hope that self-isolation and restrictions may become a thing of the past.
Speaking earlier this week, Paul Hunter, a professor in medicine at the University of East Anglia, said people with Covid should eventually be allowed to “go about their normal lives” as they would with a common cold.
“This is a disease that’s not going away. Ultimately, we’re going to have to let people who are positive with Covid go about their normal lives as they would do with any other cold,” he told BBC Breakfast.
“If the self-isolation rules are what’s making the pain associated with Covid, then we need to do that perhaps sooner rather than later. Maybe not quite just yet.
“Covid is only one virus of a family of coronaviruses, and the other coronaviruses throw off new variants typically every year or so, and that’s almost certainly what’s going to happen with Covid. It will become effectively just another cause of the common cold.
“Once we’re past Easter, perhaps, then maybe we should start to look at scaling back, depending on, of course, what the disease is at that time.”
