Time is fast running out if you're under 50 and want a Covid booster.
Chief medical officer for England Professor Chris Whitty is encouraging people to take up the vaccine before the plug is pulled this Sunday, February 12.
After then, the booster will only be offered to those considered to be at risk of serious illness.
Sir Whitty says: "We know that having the third vaccination, the booster, is a very important part of immunity to Covid and it provides additional protection."
The NHS is using Moderna's bivalent vaccine, which covers both the original Covid virus and the Omicron variant.
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"Like all medicines, this vaccine can cause side effects, although not everybody gets them, " says the UK's Medicines and Healthcare products Regulatory Agency (MHRA).
Perhaps the most common is people might experience swelling and tenderness of the underarm glands on the same side the injection took place.
Common side effects, cropping up in more than one in ten people, include:
Vomiting
Muscle ache, joint aches, and stiffness
Other things to watch for include redness where the needle went in, but this may not appear until nine to 11 days later.
Further well-documented adverse reactions could include a rash or hives at the point of injection, as well as diarrhoea.
Less common - affecting up to one in 100 people - are itchiness at the injection site, dizziness, or stomach pain.
Rarely, a condition called Bell's palsy may occur, which is when one side of the face droops temporarily.
Greggs, Costa & Pret coffees have 'huge differences in caffeine', says reportThere are have been very rare cases - around one in 10,000 - where the heart may become inflamed.
Inflammation of the heart muscle is known as myocarditis, while inflammation of the outside of the heart is called pericarditis.
Heart inflammation can lead to breathlessness, palpitations, or chest pain, which requires medical attention.
"If you get any side effects, talk to your doctor, pharmacist or nurse," the MHRA advised.
Most side effects go away within a few days.
Seek urgent medical attention if you experience any of the following:
Changes in your heartbeat
Swelling of your lips, face, tongue or throat
People are able to get the booster because they are considered at risk by the Joint Committee on Vaccination and Immunisation (JCVI).
This includes pregnant women, people who have a learning disability or severe mental illness, or another condition that makes them eligible, such as diabetes, epilepsy, blood cancer and asthma. Other chronic conditions outlined in the government's Green Book (which has the latest information on vaccines and vaccination procedures).
Around 6.4 million people are eligible for the jab due to a medical condition, and while the NHS has now invited everyone, people are also able to self-declare if they think they should have been invited or, for example, because they have only recently become eligible.
So far, around 350,000 people have self-declared as being at risk in order to get their jab.
The flu vaccine is given free on the NHS to adults who:
People aged 16 years and over:
A severe mental illness, such as schizophrenia or bipolar disorder