Is COVID-19 Reinfection Possible? – How Long Does Our Immunity Last?

In the initial days of the pandemic, it was very rare to hear about people catching COVID-19 twice. The Omicron variant of the SARs-CoV-2 virus, which first emerged in late November 2021, changed that.

While the Delta variant wreaked havoc and drove the surge in India and many other countries, the Omicron variant, although much milder, brought along a high transmission rate and an increased reinfection rate.

Omicron and its growing family of sub-variants have left us wondering whether 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 reinfection from Omicron is three times higher than it is for earlier strains of the virus.

What is COVID-19 reinfection?

According to the Centers for Disease Control and Prevention (CDC), COVID-19 reinfection means a person was infected with COVID-19, recovered, and became infected later. While most people will have some protection from repeat infections after recovering from COVID-19, reinfections do occur after COVID-19 infection.

Does immunity play any role?

After  infection with SARs-CoV-2 virus, the immune system of the body produces a strong immune response against the virus and retains the memory of it, which in turn protects against future infections.

As per the National Institutes of Health (NIN), cells that circulate in our body can recognize and kill the pathogen if it is encountered again, thus protecting against disease and reducing severity of the illness.

There are two types of immune responses triggered by the body. While the first involves B cells that produce antibodies, which is the first line of defense against an infection, the second is called killer T cells, the second line of defense.

Killer T cells can identify the infected cells and destroy them immediately before they replicate.

These two types of immunity helps avoids severe COVID infections and reduces the risk of reinfection.

Does our immunity from earlier infection wane over time?

Once a person gets infected with COVID-19, their body builds a robust immune response, remembering the virus particles and building antibodies against it. This enables the immune system to fight potential infections in the future. However, medical experts say that when our body does not come in contact with a virus for a long time, its memory of the viral particles may weaken and the production of antibodies may slow down. This is why the immunity of our body may wane over time, leading to possible reinfections.

How long does vaccine induced immunity last?

Vaccines against COVID-19 prompt the body to produce antibodies and trigger a T-cell response. However, they are different from those our body produces naturally.

COVID-19 vaccines provide strong and durable protection against severe infection and death. However, their effectiveness against infection wanes over period of time. Therefore, your risk of getting COVID-19 infection is very low shortly after the most recent vaccination dose. As per the CDC, someone who’d been vaccinated was 2.4 times less likely to test positive for the virus than an unvaccinated individual.

However, given the emergence of new COVID-19 variants like Omicron, breakthrough infections have become more prevalent and there has been a rising number of reinfections. Experts believe getting reinfected with the disease can be a possibility due the mutations in the virus genes which provides it the ability to dodge vaccine-induced immunity and diminish vaccine effectiveness in the long run.

That is why, booster shots have become the way ahead. Currently booster shots are being administered in may countries, including India. These shots help re-expose the immune system  of our body to the immunizing antigen, the memory of which could have waned after the earlier vaccine doses.

How soon can you get reinfected with COVID?

There is no definite data to show how soon we may catch COVID-19 again.

While evidence says natural immunity can last up to 90 days and well beyond that, a recent report by the CDC also says that COVID reinfection can occur sooner than you think.

Are reinfections milder?

Experts say people who have had COVID earlier can expect to experience a less severe or a milder reinfection. It is believed that a reinfected individual is likely to have some pre-existing immunity from his/her primary infection which in turn, just like vaccines, reduces the severity of the disease. Moreover, vaccinations may offer a double layer of protection against severity COVID-19 infection, especially in those who catch COVID twice.

Do reinfections strengthen immunity?

Almost certainly yes. A single, prior infection gives similar protection against infection as two doses of vaccine. Therefore, it is reasonable to assume that reinfections may also boost immunity.

However, such immunity still will not be 100% protective.

Conclusion

While both natural infection and vaccination provides a certain amount of immunity against the SARs-CoV-2 virus, experts believe new emerging variants and waning immunity has raised the risk of reinfection.

Since the detection of Omicron variant in November 2021, the number of COVID-19 reinfections have been rising sharply, a trend not observed with earlier variants. Experts opine that the new variant perhaps has the ability to evade the immune defenses of our body, which is why it may drive a surge.

In addition, the Omicron variant, due to its heavy mutations, is also said to escape vaccine-induced immunity, thereby causing increased chances of breakthrough infections as well.

Hence, experts urge people to be cautious, continue to practice COVID appropriate behaviour and most importantly, get their booster shots in time. Booster shots re-exposes the immune system of our body to the viral pathogen, triggering a strong immune response.