More than two-thirds of UK adults – 36 million people – have had a first dose of a Covid vaccine, while a third of adults are now fully vaccinated with two doses.

The UK’s vaccine committee has advised that because of concerns over the Indian variant, the over-50s and people who are clinically vulnerable should receive their second doses eight weeks after the first, instead of 12 weeks. Vaccination is being speeded up and extra testing is taking place in certain areas where cases of the variant are rising quickly.

People in their 30s are now being invited in many areas of the UK. They will be offered an alternative to the AstraZeneca vaccine, if they don’t have an underlying health condition, because of a slightly increased risk of extremely rare blood clots linked to the vaccine.

In England, people aged 38 and 39 are being invited to book online. Text messages have been sent out with a link to the national booking service, which can also be called on 119.

People aged 40 and over in Scotland are now being invited to get their vaccine. In some parts of Glasgow, appointments are being made available to 18-39 year olds.

The Welsh government says vaccines are now being offered to people aged 40 and over, and some health boards have started inviting the 30-39 age group. There’s more information about the roll-out on the Public Health Wales website.

In Northern Ireland, people aged 30 and over are now eligible. They can book online or call 0300 200 7813.

Anyone in the UK who has been invited for a vaccine but has not come forward, is urged to do so quickly.

The government says all adults will be offered their first dose by the end of July, in decreasing age order.

The UK’s vaccine committee says pregnant women should be offered a Covid 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.

Those most at risk from Covid and those caring for them were vaccinated first. They include:

All four nations of the UK follow these priorities, but the rollout varies between England, Scotland, Wales and Northern Ireland.

Everyone should be offered a second vaccine dose within 12 weeks of the first jab to be fully vaccinated against Covid-19.

People over 50 and those with severe underlying health conditions which put them a high risk from Covid will now receive their second dose sooner than originally planned – eight weeks after the first, rather than 12. This is because of concerns over a rise in cases of the India variant.

The approved vaccines require two doses to provide the best protection.

In the UK, people were initially told they would get a second dose three to four weeks after the first. But to ensure a faster rollout of first doses, the UK’s chief medical officers extended the gap to 12 weeks.

This decision has been proved correct by studies which show that one vaccine dose gives prolonged protection and cuts infections in all age groups. A second dose is still required, however, for maximum protection.

People under the age of 40 are now to be offered an alternative to the Oxford-AstraZeneca vaccine if it’s available, after a review into the numbers affected by extremely rare blood clots.

But the UK’s medicine regulator – the MHRA – says the benefits of the vaccine still outweigh the risks for most people.

A UK trial is currently investigating whether using two different vaccines for the first and second doses could give better protection and more flexibility.

At present, official guidance says everyone should get the same vaccine for both doses. In very 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 after the first dose should not, the regulator says.

All three vaccines used in the UK have been shown to be effective at preventing people from becoming seriously ill and dying from Covid.

The government’s scientific advisers say the India variant spreads more easily than the current form of the virus – but they don’t know by how much. As yet, there is no evidence the vaccines are less effective against it.

Vaccines offer good protection against the ‘Kent’ variant, which is the dominant one in the UK, and appear to protect against severe illness from other concerning variants, including the South Africa and Brazil ones.

Developers are updating their jabs to target the new variants and plan to have them ready by the autumn.

They are likely to be offered as a routine booster for the most vulnerable groups.

The UK has ordered eight vaccines and expects to receive 517 million doses – more than enough for every adult to receive two.

These include another 60 million doses of Pfizer’s vaccine (added to 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.

No decision has yet been made on whether teenagers or younger children will be offered a Covid vaccine in the UK.

The Pfizer vaccine is currently approved for use in over-16s in the UK and the AstraZeneca and Moderna vaccines for over-18s.

In Canada and the US, adolescents are set to receive the Pfizer vaccine after it was approved for use in teenagers following a trial which showed children aged 12-15 were well protected and had no unusual side effects.

AstraZeneca is trialling its vaccine on six-to-17-year-olds in the UK. Moderna and Johnson & Johnson are currently testing their vaccines on those aged 12-18, with Moderna’s data expected soon.

Moderna and Pfizer are also testing their jabs on younger children between six months and 11 years old.

No, it’s not mandatory – but everyone is being urged to get vaccinated to protect their family, friends and wider society.

The government is currently considering whether to make the vaccine compulsory for NHS staff and care workers.

A very small number of people have experienced a severe allergic reaction – known as anaphylaxis – after the Pfizer vaccine, but the UK regulator says these are “very rare”.

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 Covid 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.