All you need to know about coronavirus re-infection
With the onset of the latest variant of concern Omicron, there has been an increased possibility of catching COVID twice in a short span of time.
According to the World Health Organization (WHO), "Preliminary evidence suggests there may be an increased risk of reinfection with Omicron (ie, people who have previously had COVID-19 could become reinfected more easily with Omicron), as compared to other variants of concern, but information is limited."
That said, even though the number of COVID-19 cases have dropped considerably, the fact that re-infections have become more prevalent in recent times has alarmed health experts around the world.
What is COVID-19 reinfection?
Dr Manoj Goel, Director, Pulmonology, Fortis Memorial Research Institute, Gurugram says, "Reinfection is defined when a Covid infection recurs in a patient who had tested positive previously. The exact incidence of reinfection is not known due to the possibility of asymptomatic infection in a person who would not test himself for Covid. However, this was found to be very common in the third wave."
According to the Centers for Disease Control and Prevention (CDC), "Reinfection with the virus that causes COVID-19 means a person was infected, recovered, and then later became infected again. After recovering from COVID-19, most individuals will have some protection from repeat infections." However, as per the US health agency, reinfections do occur after COVID-19, but more research is awaited.
Also read: Coronavirus: Know why Omicron subvariant BA.2 spreads faster
How soon are people getting reinfected?
Since the onset of coronavirus, different researchers have come up with different data. While an October 2021 study reveals that for people who recover from COVID-19, immunity could last for about 3 months to 5 years, another study found that immunity could last for as long as 8 months.
However, Dr Aravinda suggests that the duration of immunity may have shortened to 4-8 weeks in the recent past.
How long does natural immunity last?
People who have contracted and recovered from COVID-19 infection can expect to have a certain level of immunity against the SARs-COV-2 virus, which means they're safe from a repeated bout of infection. However, health experts and doctors urge taking necessary measures.
While it is difficult to determine as to how long immunity from previous infection lasts, Dr. S.N. Aravinda, Consultant - Internal Medicine, Aster RV Hospital says that it could differ from person to person.
"It could last from a few months to a period of a year. It depends on how each individual’s immunologic system reacts to the virus. Coronavirus is similar to cold, the natural immunity would eventually wear off. One may also develop immunity against one variant and still be affected by another variant," he adds.
The science behind waning immunity
Currently, scientists and medical professionals are uncertain as to how long protection from a natural infection or vaccine immunity lasts. While the duration of natural immunity is not exactly known, Dr. Goel suggests it could last from 3 to 12 months.
He is of the opinion that the Immunity gradually wanes over a period of time due to fall in the levels of protective antibodies and T cells.
After an infection or vaccination, your body builds a strong immune response and fights against possible future infections with the help of antibodies. However, when your body does not come in contact with the viral pathogen for a long period of time, the production of antibodies slows down, the cells and proteins gradually diminish causing your immunity to start to wane.
Additionally, according to Dr. Aravinda, the major reason behind diminishing immunity is the emergence of different COVID variants.
"Even if one develops immunity against one variant it does not mean that they have developed immunity against all of them. The body is continuously evolving and adapting to the environment. When one takes a vaccine, the body remembers the behavior pattern of that virus and is prepared to fight it – this is called immunologic memory. Over time this will gradually decline," he says.
When is one most prone to COVID reinfection?
COVID-appropriate behaviour plays a key role in determining who is more or less protected from the virus.
"A person who is not following Covid protective behaviour, those who have deferred vaccination and immunocompromised people consisting of old age, diabetes patients, heart, lung disease and cancer patients are more prone to COVID-19 re-infection," says Dr Goel.
Dr Aravinda is of the same opinion and says that when strict guidelines are in place and people are being cautious, the spread of virus declines. "One is most prone to severe Covid infection if they have comorbidities or other underlying health issues that they are not aware of. One is prone to Covid infection if they do not follow safety protocols," he says.
According to him, "It depends on the variant too; the Omicron variant was found to be highly infectious. We advise people to stay cautious and follow safety protocols."