The gap between Covid jabs for over-40s in England and Scotland will now be eight weeks rather than 12.

The change has been made because of concerns about the Delta variant.

Meanwhile, in England, over 21s can now book jabs – and vaccinations will become compulsory for care home staff.

As well as bringing forward second doses for over-40s, the government has also said:

In England, people aged 21 and over can book online or call 119.

Across the rest of the UK:

All vaccines being used require two doses to provide the best protection. In order to give as many people as possible a first dose, the initial UK advice was to offer jabs 12 weeks apart.

In England people over 40 and those with severe underlying health conditions can now receive their second dose after eight weeks.

Health Secretary Matt Hancock said the NHS would contact people to bring forward their appointments.

You can also rearrange an appointment yourself, but you must first cancel your original booking. You can do this online, or by calling 119. You cannot see availability for earlier appointments until you have cancelled.

Your second dose will be the same type as your first. It may be easier to arrange an earlier jab for AstraZeneca as supplies are relatively good. Pfizer is being used alongside Moderna for under-30s.

Second doses are also being brought forward in Scotland. Anyone whose second appointment is more than eight weeks after their first can rebook it via the NHS Inform website.

In Northern Ireland, the interval between doses has been reduced from 10 weeks to six weeks for appointments scheduled after 14 June 2021.

In Wales, the government says vaccination clinics “are accelerating second doses”, and that people will be contacted by their local health board in due course.

The roll-out has largely been organised by age, but other people prioritised include:

How many people have been vaccinated so far?

Vaccinations are to become compulsory for staff at care homes in England, Mr Hancock has said.

He described the move as “sensible and reasonable” and said he would consult on extending it to the NHS.

Workers will have 16 weeks to get both jabs, once regulations are approved by Parliament.

For everyone else, vaccination is not compulsory but everyone is being urged to get jabbed.

The UK is using vaccines made by Pfizer-BioNtech, Oxford-AstraZeneca, and Moderna.

People under 40 are being offered an alternative to the Oxford-AstraZeneca vaccine because of concerns about a possible connection with extremely rare cases of blood clots.

But the UK’s medicines regulator says the benefits of the vaccine outweigh the risks for most people.

A single-dose Covid vaccine made by Janssen has also been approved for use in the UK by the medicines regulator. Twenty million doses have been ordered for the UK and will arrive later this year.

The Delta variant is believed to be around 60% more infectious than the previous dominant variant in the UK, the Alpha. It’s also thought to be twice as likely to result in hospital admissions.

However, new analysis by Public Health England (PHE) shows that two doses of either the Pfizer or AstraZeneca vaccine were highly effective at preventing hospital admissions for infected patients.

PHE said this is similar to the amount of protection vaccines provide against the Alpha variant.

Vaccine developers are updating their jabs to target new variants more effectively but it’s not clear when they will be ready.

A UK trial is investigating whether using two different vaccines could give better protection and more flexibility.

At present, official guidance says everyone should get the same vaccine for both doses. But in rare circumstances – if only one vaccine is available, or it’s not known which was given for the first dose – a different vaccine can be used.

If you have already had a first dose of the AstraZeneca vaccine, you should also have a second dose. Only those who suffered a rare blood clot should not, the regulator says.

A decision to vaccinate all 12 to 17-year-olds is unlikely to be recommended by UK vaccine experts imminently, the BBC has been told.

Certain groups of children may still be offered a Covid jab – but not all.

A statement from the Joint Committee on Vaccination and Immunisation (JCVI) is expected in the coming days.

Vaccinating children could help protect other people, but the risk to youngsters from catching Covid remains extremely low.

The Pfizer vaccine has now been approved as safe for 12 to 15-year-olds in the UK.

Moderna says its Covid vaccine is “highly effective” in adolescents aged 12-17, and it will soon ask global regulators to approve its use for this age group.

The following trials are happening:

People are being urged to take part in trials to find out whether a third dose could protect against new variants.

The Cov-Boost study will recruit 3,000 people of all ages to test whether re-vaccinating some people in the autumn is necessary.

The UK has ordered eight vaccines and expects to receive 517 million doses.

These include another 60 million doses of the Pfizer vaccine (on top of the original order of 40 million) to be used as part of a booster programme in the autumn.

Vaccines supplied by CureVac will be designed to protect against the most concerning new variants.

The UK’s vaccine committee says pregnant women should be offered a jab when other people their age get one.

The Pfizer and Moderna vaccines are preferable, they say, because data relating to 90,000 pregnant women has not raised any safety concerns.

Data on how the AZ vaccine works in pregnant women may become available in the near future.

A very small number of people have experienced a severe allergic reaction – known as anaphylaxis – after the Pfizer vaccine.

You should discuss any serious allergies with your healthcare professional before being vaccinated.

Most people will not be affected in any way, although side-effects with all vaccines are possible.

The most common ones include a sore arm, headache, chills, fatigue and nausea.

They are part of the body’s normal immune response to vaccines and tend to resolve within a day or two.