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Can you test positive for Covid after booster jab? What a positive lateral flow test means after vaccine

The booster jab will reduce your risk of becoming seriously unwell if you do catch Covid

More than 36 million people in the UK have now received a third Covid vaccination or booster dose, but is it possible to test positive after having the jab?

Here’s what you need to know.

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Can a Covid booster cause you to test positive for the virus?

No. None of the Covid vaccines will cause you to test positive for the virus after being jabbed.

Covid tests are used to see whether or not you currently have an infection and the vaccines do not use live versions of the virus, so they won’t show up on a Covid test.

However, it’s worth remembering that the booster jab may take around a week to be effective, so in that time, you may still contract the virus while your antibodies build back up in your immune system.

The booster jab will reduce your risk of becoming seriously unwell if you do catch Covid. (Picture: NationalWorld)

Can you catch Covid after the booster jab?

Although it is much less likely, it is still possible to catch Covid-19 after having a booster dose.

However, getting the booster will reduce your risk of becoming seriously unwell if you do catch the virus, as well as offering you longer-lasting protection.

The need to wait 15 minutes after your vaccine has now been suspended, due to very few people having serious reactions to the vaccine, but you should still be monitored for 15 minutes if you have had a past history of anaphylaxis or severe allergic reactions, so that if you do have a severe reaction, help will be at hand.

How effective is the booster vaccine?

Several studies have shown that boosters can give a big increase in protection against illness from Covid-19.

A  real-world study by the UK Health Security Agency found that two weeks after a booster dose, protection levels increased to 93.1% for those who had AstraZeneca for their first two doses and 94% for those who had Pfizer.

Findings from the UK-based Cov-Boost trial published in the Lancet also showed that all the available booster vaccines improved immunity against Covid-19, regardless of which vaccine had been used as a first dose, with all the booster vaccines leading to an increase in antibodies that target the virus.

Evidence also shows that a booster dose will offer much greater protection against the Omicron variant than two doses of the vaccine. A study by the UK Health Security Agency suggests that Covid-19 boosters are 70 to 75% effective at preventing illness from Omicron in the early period after vaccination.

What are the side effects of the booster?

Side effects from the booster are usually similar to those experienced after a second dose.

If you do experience side effects, they are likely to be mild and last no more than a few days. You can also take paracetamol to treat them.

The booster jab will reduce your risk of becoming seriously unwell if you do catch Covid (Photo: Shutterstock)

The most common side effects of the booster are:

  • pain or heaviness in the arm and shoulder area where you had the injection,
  • feeling tired
  • a headache
  • fever or chills
  • aches or muscle pain
  • general flu like symptoms

If you have a fever following your booster jab that lasts longer than a couple of days, or you have any other Covid-19 symptoms, you should stay at home and get a test.