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Can you become immune to COVID-19?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on Dec 14, 2020.

Official Answer

by Drugs.com

Key Points

  • Recent studies from Oxford Biomedical Research Centre suggest that those who have had COVID-19 are unlikely to contract the illness again for at least 6 months. Researchers are still actively investigating if antibody immunity will protect against reinfection with COVID-19 disease long-term.
  • Most people who are infected with COVID-19 develop an immune response within the first few weeks, but the protective effect of this response is not fully known.
  • In those who have been previously infected with SARS-CoV-2, re-infection appears to be uncommon at this point, although there have been reports, according to WHO.
  • Vaccination programs started to roll out in December 2020 in the US. Length of immunity due to vaccine protection is also not yet confirmed, but seems to be at least 6 months, if not longer. Whether or not re-vaccination for COVID-19 will be needed is not yet known.

If there is any one good thing about catching the novel coronavirus known as SARS-CoV-2, it’s that you may have built an immunity to the virus to help prevent further COVID-19 disease. It’s estimated about 80% of people will recover from the virus without serious symptoms.

But how long can your coronavirus immunity last? Will it be lifelong protection, as with measles or chickenpox, or just short-lived, as with the influenza vaccine? How robust will your immune response be to a future coronavirus infection if you’ve had only mild symptoms -- or no symptoms at all?

Immunity with other coronaviruses does decline over time, as is seen with the common cold, SARS-CoV-1 and Middle East Respiratory Syndrome (MERS).

How do you become immune to COVID-19?

Your immune system uses an advanced network to recognize a virus you’ve had before, and releases antibodies to fight it off again. Antibodies are proteins made by your immune system to fight infection.

Your body is geared to recognize foreign substances, like bacteria and viruses, and produces antibodies to recognize these invaders in your blood. Antibodies are produced in response to an infection and help to prevent reinfection -- or lessen severity of infection -- from the same illness.

Antibodies can differ in how well they work:

  • For example, some illnesses like measles or chickenpox, are fought off for a lifetime because your immune system memory always recognizes the virus to keep it at bay.
  • Other viruses, like seasonal influenza, can mutate from season to season, so a new flu vaccine is needed each year.
  • Immunity to certain viruses, such as the common cold, is very short-lived -- possibly only a few months.

Antibodies are often short-lived, but memory cells, such as B-cell and T-cells, can outlast antibodies and kick into gear years after an infection.

The COVID-19 vaccines also stimulate the immune system to make antibodies against the virus.

Do other coronaviruses lead to immunity?

To develop answers, scientists are looking at clues from the past.

The common cold is an example of a coronavirus where immunity is short. In an experiment with coronaviruses that lead to the common cold, researchers infected volunteers to see if a rechallenge -- reinfecting with the same virus a year or so later -- would lead to symptoms. Antibodies do seem to appear with the coronavirus that causes a cold, but their levels decline quickly over time.

Patients who recovered from the 2002 SARS-CoV, a coronavirus closely related to the current SARS-CoV-2, appear to have antibody protection for about two years. How strong this immune defense is against reinfection is not known.

For the Middle East Respiratory Syndrome coronavirus (MERS-CoV), a more serious viral respiratory disease from 2012, there were only about 2500 cases over eight years. The mortality rate of MERS was about 35%, but survivors did generate an immune response detected for up to two years.

How long will immunity last after a COVID-19 infection?

It is not yet fully known how long immune protection will last for patients with SARS-CoV-2, but recent research is providing clues. It appears immunity may be at least 6 months and maybe longer. At this point, re-infection with the coronavirus appears to be a rare event in most people, although there have been a few reports.

A recent study by NHIR Oxford Biomedical Research Centre and Public Health England is investigating the immune response after infection with COVID-19. Researchers looked at a 30-week period with 12,180 healthcare workers at Oxford University Hospitals. Staff were tested for COVID-19 antibodies and were retested if they exhibited symptoms as part of regular hospital testing.

Researchers followed to see the number of newly infected staff who had tested positive for antibodies compared to those who had not shown antibodies.

  • Results showed that 89 of 11,052 workers without antibodies were infected later with symptomatic COVID-19.
  • Of the 1,246 staff with antibodies, none developed symptomatic COVID-19.
  • The number who tested positive when they had asymptomatic COVID-19 were higher in the group without antibodies - 76 staff without antibodies tested positive compared to just 3 with antibodies, and these 3 remained well and did not develop symptoms.

These results suggest within 6 months of a COVID-19 infection, most people are unlikely to get infected again. Researchers are now following participants from this study to determine how long their immunity might last.

Are antibodies available to treat COVID-19?

Not only do we produce antibodies naturally, they can also be created in a lab setting as monoclonal antibodies. Monoclonal antibodies may provide benefit when given early after COVID-19 diagnosis in patients with high viral load or who have not mounted an immune response.

A cocktail of monoclonal antibodies known as casirivimab and imdevimab was granted emergency use authorization (EUA) by the FDA in November 2020. The EUA is based on Phase 2 positive results from studies done by Regeneron Pharmaceuticals. The first 799 adult COVID-19 outpatients were evaluated in the ongoing, placebo-controlled study.

The outpatient clinical trial suggests that monoclonal antibodies such as casirivimab and imdevimab have the greatest benefit when given early after diagnosis and in patients who have not yet mounted their own immune response or who have high viral load.

  • Casirivimab and imdevimab given together are authorized to treat mild to moderate COVID-19 in adults, as well as in pediatric patients at least 12 years of age and weighing at least 40 kg.
  • These patients should have received positive results of direct SARS-CoV-2 viral testing and are at high risk for progressing to severe COVID-19 and/or hospitalization.
  • The recommended dose is 1,200 mg of casirivimab and 1,200 mg of imdevimab (2,400 mg total) given as a single intravenous (IV) infusion.
  • Casirivimab and imdevimab are not authorized to be used in patients who are hospitalized or require oxygen therapy due to COVID-19, or for patients using oxygen therapy due to another illness but require an increase in baseline oxygen flow rate due to COVID-19 due to possible worsened outcomes.

The manufacturer states that casirivimab and imdevimab may be most beneficial in patients at risk for poor outcomes due to high viral load, ineffective immune response at baseline or pre-existing risk factors. Research continues with the antibody cocktail in

Bottom Line

Patients who recover from COVID-19 make antibodies to the virus. Research is ongoing to determine how well these antibodies or memory cells protect people from reinfection, and for how long. Current research suggests immunity may last at least 6 months, but possibly longer.

Pfizer's COVID-19 vaccine has received an EUA from the FDA and vaccinations started in Dec. 2020 for healthcare providers and the elderly. Other vaccines are in research or under FDA review, and one monoclonal antibody cocktail has received Emergency Use Authorization for treatment of outpatients with the virus. Vaccines have been shown to elicit a strong immune response to prevent infection, and monoclonal antibodies can provide an external source of antibodies to fight off infection early in the disease.

Immunity through an effective and safe vaccine will be the best mode to control the spread of SARS-CoV-2. Infectious disease experts expect the vaccine roll-out to continue in the US and widespread availability for the general public is expected by spring to summer of 2021. A COVID-19 vaccine may not be available for younger children under 16 years of age until more studies are completed.

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