How long do vaccine side effects last? Covid booster jab symptoms explained - and when they’ll go away

The booster jab is thought to trigger an immune response to fight Covid within just two to three days

Adults across the UK are being urged to get their Covid-19 booster vaccination to help protect against the Omicron variant.

More than 100,000 coronavirus cases were recorded in a single day for the first time in the UK last week, as the highly transmissible strain continues to spread.

A booster dose can significantly reduce the risk of symptomatic Covid-19 infection (Photo: Getty Images)

The UK government has declared a “national mission” to offer a booster vaccine dose to everyone who is eligible by the end of the year in a bid to boost immunity levels and keep infections under control.

If you have yet to get your booster jab, here’s what you need to know about the side effects and how long they last.

What are the side effects of the booster jab?


As with the first and second doses, it is common to experience some side effects after getting your booster.

The severity of symptoms will vary from person to person, but in most cases effects should be mild.

It is also possible not to suffer any side effects at all.

The most commonly reported symptoms after vaccination include:

  • a sore arm at the site of the injection
  • muscle aches
  • joint pain
  • fever
  • chills
  • tiredness
  • headache
  • nausea

When will I start to feel better?


Side effects from the booster jab typically only last for a two to three days and should improve as time goes on.

A sore arm can be one of the longest lingering effects of the jab and it may feel tender to touch for around three days.

Moving your arm after you have been vaccinated should help to reduce soreness as this will stimulate the blood flow, while applying a cold compress can also help.

The NHS recommends taking over-the-counter painkillers, such as paracetamol, and getting plenty of rest to help ease symptoms after vaccination.

If your symptoms get worse and you are concerned, you should call 111 for advice.


When will the booster start to work?

The booster jab is thought to trigger an immune response within just two to three days, rather than weeks, according to scientists.

This is a much quicker response than the two weeks the first jab takes to prime the immune system to fight the virus.

The faster response is due to the fact that crucial memory cells activated after the first dose are still present in the body, and so they “do not require the two-week activation and instruction phase they initially go through”.

These memory cells – T and B – seek out infected cells and produce antibodies that stop Covid-19 from gaining entry in the first place, and mean the immune system is on alert for any sign of the virus.

Will the booster protect against Omicron?


A booster dose can significantly reduce the risk of symptomatic infection with the Omicron variant, according to health officials.

Early analysis by the UK Health Security Agency (UKHSA) found that a third dose prevents about 75% of people from getting any symptoms.

While this has since been revised down to 70%, a third jab is thought to offer even higher protection from hospitalisation and death.

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