How long does COVID-19 immunity last?

Immunity to COVID-19 is currently thought to last between 8 months to a year. Immunity depends on several factors - including whether you have recovered from coronavirus or have been vaccinated.

When your body comes under attack from COVID-19, it mounts one of two immune responses.

• B cells create antibodies that stick to the virus so your immune system can identify and destroy them to prevent the virus from entering your cells.
• T cells are activated when your body detects a virus. They attack and kill any of your cells that are infected with the virus.

After you recover from infection, the B cells, their antibodies, and T cells remember the virus to build immunity.

If you’ve recovered from COVID-19, you could be immune for up to 8 months or more. The length of natural immunity varies from person to person. COVID-19 has only been around for a year, so more research is still needed to fully understand how long immunity lasts after infection.

Current research shows that roughly 90% of recovered patients have detectable anti-SARS-CoV-2 antibodies for several weeks or months after their infection.

Studies on the reinfection of healthcare workers show that COVID-19 antibodies offer roughly 95% protection against COVID-19 symptoms and 75% protection against infection.

Yes, your amount of antibodies against COVID-19 can decline over time. This means your body’s immune response will gradually become weaker and eventually lose immunity altogether.

Many factors can affect your immune response to COVID-19, and the immune response tends to differ from person to person.

Factors like age play a part in the level of immunity generated by an individual. Some early studies suggested that older people are less likely to build an effective immune response to infection and vaccination. But, recent studies contradict this, with some showing more significant immune responses in older people than younger adults.

There is some evidence of a reduced antibody response in children compared with adults. Other factors at play in reducing effective immune responses include immunodeficiency diseases, autoimmune diseases, or those taking certain types of medication.

Scientists estimate that immunity to COVID-19 after vaccination will last up to one year. However, it’s important to note that COVID-19 vaccination programmes are under a year old and too recent for accurate research into immunity length.

Research into the effects of the Pfizer and AstraZeneca vaccines shows a good immune response in most patients. A single dose of the Pfizer vaccine, mounted a “robust immune response” in 99% of cases after just one jab, according to research on the immunity of health workers by the Universities of Oxford and Sheffield.

A similar study of 350,000 people by Oxford University and the Office for National Statistics, found a 65% drop in COVID-19 infections, just 21 days after a single dose of AstraZeneca or Pfizer. And after the second Pfizer jab, symptomatic infections fell by 90%.

Vaccination immunity is also shown by a drop in hospitalisations of people who have been vaccinated.

After 1 shot of the Pfizer or Oxford/AstraZeneca vaccine, hospital admissions fell by 85% and 94% respectively.

Despite these positive results, it’s important to remember that immune response varies from person to person. We still don’t know if COVID-19 vaccines stop people from becoming infected or whether they can still go on to become infectious.

Yes, in some cases, people may not build an effective immune response. People at risk of a weaker immune response include older people or those with suppressed immune systems. But when developing the COVID-19 vaccine, the Pfizer/BioNTech, Moderna and Oxford/AstraZeneca teams found similar immune responses in older people and younger people.

Yes, it is possible to carry and transmit COVID-19, even if you have been vaccinated or recovered from a natural infection.

Current research on the three COVID-19 vaccinations available in the UK (Pfizer, Moderna, Oxford-AstraZeneca), shows that all three vaccinations prevent people from getting sick. But we don’t know if being vaccinated prevents people from becoming infected with COVID-19 - or passing it to someone else.

So even if you have been vaccinated and feel well, there’s a chance you could be carrying and spreading the disease unknowingly.

Scientists currently estimate that booster shots will be required every year. So even if you’ve been vaccinated, you might need a booster shot to top-up your immunity to COVID-19.

In May 2021, British Vaccine Deployment Minister Nadhim Zahawi said clinicians were reviewing how long vaccine protection was lasting, before rolling out the booster shot programme. But he said the government was planning to deliver booster shots from as early as September, 2021.

He added that clinical trials are currently reviewing the effects of mixing vaccines, to assess the protection of different booster shots.

Viruses continuously change through mutation. This causes new strains to occur, like the Kent, Indian, South African and Brazilian variants - dubbed the “variants of concern”.

Let’s take a look at what the research says about the effectiveness of vaccines against the 4 dominant new strains.

Indian variant: Research by Public Health England shows the AstraZeneca jab is 60% effective against the Indian variant after two doses. It is 33% effective after just one dose.

Kent variant: Research shows the AstraZeneca vaccine provides good protection of up to 75% against the Kent strain of COVID-19. To put that in context, the World Health Organization recommends vaccines to have a minimum of 50% protection.

South African variant: A study of 2,000 people in South Africa showed that the AstraZeneca vaccine offers only minimal protection against mild cases of the South African variant. However, it is likely to prevent serious cases and deaths.

Brazilian variant: Early results show that the AstraZenaca vaccine is only slightly less effective against the Brizilian variant than for the original strain of COVID-19. But research is still ongoing.

Indian variant: Research by Public Health England shows the Pfizer vaccine is 88% effective against the Indian variant after two doses. It is 33% effective after one dose.

Kent variant: Research suggests the Pfizer vaccine offers good protection against the Kent variant.

South African variant: Results are mixed. Early lab studies show the Pfizer vaccine is less effective against the South African strain of COVID-19. Recent studies are more positive. A study of 800 people in South Africa showed that the Pfizer vaccine was 100% effective against the South African strain.

Brazilian variant: Studies show that antibodies generated by the Pfizer vaccine remain effective and active against the Braziliant variant.

Indian variant: Research is still ongoing into the effectiveness of the Moderna vaccine against the Indian strain of COVID-19.

Kent variant: Early studies show that antibodies made in response to the Moderna vaccine are effective against the Kent strain of COVID-19.

South African variant: Research shows that the Moderna vaccine is effective against the South African variant, but with a weaker and shorter immune response.

Brazilian variant: The Moderna vaccine is effective in producing antibodies against the Brazilian strain of COVID-19. However, they are slightly less effective than for earlier strains of COVID-19.