Is re-infection with COVID-19 possible? – How long does our immunity last?
In the early days of the pandemic, it was very rare to hear of people contracting COVID-19 twice. The Omicron variant of the SARs-CoV-2 virus, which first appeared at the end of November 2021, changed that.
While the Delta variant wreaked havoc and spawned the wave in India and many other countries, the Omicron variant, while much milder, brought a higher transfer rate and increased recontamination rate.
Omicron and its growing family of subvariants have us wondering if we have enough immunity to protect against the ever-changing virus.
According to a study conducted by South African scientists in December 2021, the risk of re-infection from Omicron is three times higher than with previous strains of the virus.
What is COVID-19 reinfection?
According to the Centers for Disease Control and Prevention (CDC), reinfection with COVID-19 means that a person was infected with COVID-19, recovered, and later became infected. While most people will have some protection against re-infection after recovering from COVID-19, reinfections do occur after a COVID-19 infection.
Does immunity play a role?
After infection with the SARS-CoV-2 virus, the body's immune system produces a strong immune response against the virus and maintains memory of it, which in turn protects against future infections.
According to the National Institutes of Health (NIN), cells circulating in our bodies can recognize and kill the pathogen if it is encountered again, protecting them from disease and reducing the severity of the disease.
There are two types of immune responses that are triggered by the body. While the first involves B cells that produce antibodies, which are the first line of defense against an infection, the second involves killer T cells, which are the second line of defense.
Killer T cells can identify the infected cells and destroy them immediately before they multiply.
These two types of immunity help prevent severe COVID infections and reduce the risk of re-infection.
Does our immunity to previous infections decline over time?
Once a person becomes infected with COVID-19, their body mounts a robust immune response, remembering the virus particles and building antibodies against them. This allows the immune system to fight off possible infections in the future. However, medical experts say that when our body does not come into contact with a virus for a long time, the memory of the virus particles can weaken and the production of antibodies can slow down. This is why our body's immunity can decrease over time, leading to possible re-infections.
How long does vaccine-induced immunity last?
Vaccines against COVID-19 prompt the body to produce antibodies and initiate a T-cell response. However, they are different from the ones our body produces naturally.
COVID-19 vaccines provide strong and durable protection against severe infection and death. However, their effectiveness against infection decreases over time. Therefore, your risk of getting a COVID-19 infection soon after the most recent vaccination dose is very low. According to the CDC, someone who was vaccinated was 2.4 times less likely to test positive for the virus than an unvaccinated person.
However, given the emergence of new COVID-19 variants such as Omicron, breakthrough infections are becoming more common and there is an increasing number of re-infections. Experts believe reinfection with the disease may be a possibility because of the mutations in the virus genes that give it the ability to evade vaccine-induced immunity and reduce the long-term effectiveness of the vaccine.
That's why booster shots have become the way forward. Currently, booster shots are administered in some countries, including India. These injections help to re-expose our body's immune system to the immunizing antigen, the memory of which could have been diminished after the previous vaccine doses.
How quickly can you become infected with COVID again?
There is no definitive data to show how soon we could catch COVID-19 again.
While there is evidence that natural immunity can persist for up to 90 days and much beyond, a recent report from the CDC also says that COVID reinfection may occur sooner than you think.
Are re-infections milder?
Experts say people who have had COVID before can expect a less severe or milder reinfection. It is believed that a re-infected individual is likely to have some pre-existing immunity to his/her primary infection which in turn, like vaccines, reduces the severity of the disease. In addition, vaccinations can provide double protection against the severity of a COVID-19 infection, especially in those who contract COVID twice.
Do reinfections boost immunity?
Almost certainly yes. A single, previous infection provides comparable protection against infection as two doses of vaccine. Therefore, it is reasonable to assume that re-infections can also boost immunity.
However, such immunity will still not be 100% protective.
While both natural infection and vaccination provide some degree of immunity against the SARs-CoV-2 virus, experts believe that new emerging variants and waning immunity have increased the risk of reinfection.
Since the discovery of the Omicron variant in November 2021, the number of COVID-19 reinfections has risen sharply, a trend not seen with previous variants. Experts believe that the new variant may have the ability to evade our body's immune defenses, which is why it could cause a surge.
In addition, due to its heavy mutations, the Omicron variant would also escape vaccine-induced immunity, also increasing the likelihood of breakthrough infections.
That's why experts are urging people to exercise caution, continue with appropriate COVID behaviors, and most importantly, get their booster shots on time. Booster shots re-expose our body's immune system to the viral pathogen, triggering a strong immune response.
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