The UK’s four chief medical officers have raised the Covid alert level to 4, its second highest level. This means the virus is in general circulation, transmission is high and direct Covid-19 pressure on healthcare services is widespread and substantial or rising.

The move to level 4 comes as UK cases are nearly back to peak levels last seen in January and cases of the new variant of concern, Omicron, have been doubling every two to three days. Within just five days, cases of Omicron rose from 249 to 1,576 – a six-fold increase.

Sajid Javid has warned that the Omicron variant is spreading with enormous speed and already accounts for roughly 40% of Covid infections in London; and while the number of people hospitalised with Covid-19 is on a downward trajectory in Scotland, Wales and Northern Ireland, the number of admissions is starting to rise again in England.

The chief executive of the UK Health Security Agency (UKHSA), Dr Jenny Harries, has similarly warned that we will likely see a "staggering" number of Covid cases over the next few days and the new variant is "probably the most significant threat we've had since the start of the pandemic".

Can the Omicron variant evade vaccines?

While scientists remain confident that the Omicron variant does not evade Covid-19 vaccines, early estimates suggest that vaccine effectiveness against symptomatic disease with the Omicron variant is significantly lower compared to the Delta variant.

UK data shows moderate to high vaccine effectiveness of 70 to 75% in the early period after a booster dose, however, having just two doses offers significantly less protection at 30 to 40% (with the last dose given three or more months ago).

For this reason, the Prime Minister, Boris Johnson, addressed the nation over the weekend to announce that the government is launching the ‘Omicron emergency booster national mission’, meaning every eligible adult in England will be offered their booster by the end of December. Johnson said the emergency booster mission “will require an extraordinary effort.”

Indeed, if every adult is to receive their booster shot by the end of December, the NHS will need to administer roughly one million doses per day.

So far, the record number of boosters delivered in a single day was 844,000 jabs. On Saturday, around 530,000 were boosted. This means the NHS needs to roughly double what they are currently achieving and maintain it every single day (including Christmas day) until the end of the month.

Since the announcement, demand for boosters has been enormous. In fact, the day after Johnson made his announcement, the booster booking website crashed and the NHS temporarily ran out of home-delivered lateral flow tests.

Are the goals of the emergency booster mission achievable?

Many are concerned the emergency booster programme proposes an unrealistic target given the huge amount of pressure the NHS is already under. However, measures are in place to accelerate the programme.

The government has announced that thousands more volunteer vaccinators will be trained and 42 military planning teams will be deployed across every health region, creating additional vaccine sites and mobile units. Opening hours will also be extended so that clinics are open seven days a week, with more appointments early in the morning, in the evenings and on weekends.

The Prime Minister has said that focusing on boosters will mean that some nonemergency healthcare appointments will need to be postponed until the new year. He added: “If we don’t do this now, the wave of Omicron could be so big that cancellations and disruptions, like the loss of cancer appointments, would be even greater next year.”

The number of face-to-face interactions will also be reduced and the 15-minute waiting time after the vaccine will be scrapped, allowing vaccinators the chance to see a greater number of people in a shorter space of time.

Even with these added measures, health leaders are concerned that the accelerated booster programme could put added pressure on already exhausted healthcare professionals.

Health leaders do not want to see the NHS "unfairly criticised" for the unintended consequences of the booster programme

In response, Matthew Taylor, chief executive of the NHS Confederation, said: “The Government has sent a very clear message to the NHS that ramping up Covid-19 jabs, including boosters, must be its number one priority due to the intensifying concerns about Omicron. The NHS will therefore do everything it can to get even more vaccines into people’s arms so that the public has the maximum possible level of protection.

“A similarly crystal-clear message must be sustained with the public that while the NHS will remain open for business including for urgent treatment, this enhanced focus on vaccinations could lead to disruption elsewhere in the service.

“Health leaders recognise the Government has made a strategic assessment of risk but after everything their teams have been through over the last two years, they do not want to see the NHS, including primary care, unfairly criticised for the unintended consequences of this policy.”

He added that NHS frontline staff are exhausted and working in a very pressured environment and for this reason, will need honesty and ongoing support from the government.

The Royal College of GPs (RCGP) have said they too are concerned about the pressure that general practice is currently under. Professor Martin Marshall, Chair of the RCGP, said NHS England must urgently provide GPs with guidance about how to “de-prioritise non-essential work”.

He added: “Amidst the chronic shortage of family doctors and other team members in general practice, the profession will also need to be supplemented by additional staff, perhaps redeployed from elsewhere in the NHS, retirees and medical students, and volunteers.”

Will the booster programme do enough to stave off another lockdown?

Experts warn that while booster jabs are a crucial part of protecting the public from the virus, to have the greatest impact, the size of gatherings should also be restricted.

Prof Christina Pagel, of University College London, told The Guardian that some current policies appeared contradictory, including letting vaccinated people take tests instead of isolating after contact with a Covid case.

“Don’t go to work but go to parties. Get a booster, but it’s fine not to isolate if you’re vaccinated. It’s not consistent,” she said. “This idea that kids can go to school if someone in their house has Covid is just stupid. We should be saying no parties, no gatherings bigger than 10 people, say. We need to think about moving back down the roadmap and restricting contact.”

She added: “I just don’t think they [ministers] can say ‘this is it’ until Christmas when things are so uncertain.”

While roughly 70% of the UK’s population are double jabbed, so far, only around a third (35%) have received their booster dose. This means that the majority of the population are currently relatively unprotected from the virus, hence the urgency from the government to accelerate the booster programme.

Does Omicron cause more severe disease?

The Health Secretary, Sajid Javid, recently announced that 10 people in England are in hospital with Omicron, and sadly, now one has died.

Scientists cannot currently say if the new variant causes more or less severe disease then the delta variant, as the head of advisory cabinet to the Health Ministry, Prof Ran Balicer, explains: “Not enough time has passed to understand the rate of severe illness among vaccinated patients and a rate of severe illness among the non-vaccinated has yet to be presented.”

However, the Prime Minister warned in his speech that even if the new variant doesn’t increase the risk of getting seriously ill, it is so much more transmissible that there is already a huge risk that levels of hospitalisation could overwhelm the NHS and lead to many deaths.

Data from a study by the National Institute for Infectious Diseases in South Africa has also shown that Omicron is three times more likely to cause a repeat infection than the Delta variant, meaning those who have already had the virus are more likely to get re-infected.

MPs have now voted in favour of new interventions to help slow the spread of the virus

MPs have now voted for the introduction of new interventions to help slow the spread of Omicron. The new measures mean that all adults in England must now show a ‘Covid pass’ (proof of double vaccination) or proof of a negative lateral flow or PCR test to attend certain events, such as nightclubs, concerts and sports matches.

The Commons also backed the continuation of mandatory mask-wearing in most indoor settings and compulsory vaccination for NHS workers in England.

Health leaders hope that these new interventions will help to keep the NHS afloat through the winter and limit further deaths as much as possible. As Taylor says: “We may find that these measures are not enough, but with independent modelling suggesting that Omicron could cause up to 75,000 deaths in England and over 490,000 hospitalisations by the end of April, it would be irresponsible not to give them a go.”