Can you get reinfected by COVID? How long does the immunity last?

Corona virus is an infection that has caused a global pandemic, and gaining immunity against it is the only way forward. Vaccines against COVID-19 are being developed by scientists around the world and hopefully, successful corona virus vaccination will prevent the spread of this disease. Recent news from HongKong has now questioned the efficacy of the developing vaccines, and whether they can prevent re-infection.

It is important to know the difference between a relapse and reinfection, how often it happens, and measures people need to take to protect themselves when they are out in public. This helps to improve treatment procedures and get a better understanding of the novel Corona virus. Experts suggest this is not a cause for concern and that reinfection is a very rare occurrence. From a layman’s point of view, it is important to learn the process of testing and its limitations, as well as avoid stress over COVID-19 reinfection.

One obstacle to consider is the test in itself. The RT/PCR test, which is the standardized test that is used along with the swab detects Corona virus infection in 70% of the patients. However, 30% of the cases are prone to be false negatives. Another important issue is that the test does not differentiate between live and dead viruses. So what is interpreted as reinfection, may well be dead virus particles present in recovered patients resulting in False Positives.

How do you develop immunity against Corona virus?

The human body has two modes of defence against invading microorganisms. The first is the innate immunity, which is activated when a minute a foreign particle is detected. The release of chemicals causes inflammation and stimulates white blood cells to attack the infected cells.

The cellular response or the adaptive immune response involves the production of targeted antibodies that stick to the virus and enable T cells to engulf the infected cells. The production of targeted antibodies takes about ten days and the sickest patients develop the strongest immune response. People who show only mild symptoms may not develop a sufficient immune response.

How long does immunity against Coronavirus last?

How long do the antibodies last in your system after infection by Coronavirus?

Like our own memory, our immune system remembers some infections very well but tends to forget some others. For example, the vaccine given for measles, the MMR vaccine, provides life-long immunity against the disease. However, some flu vaccines require an annual dose, as the antibodies last only for a limited period in the immune system.

Coronavirus has not been around long enough to exactly establish how long the antibodies against it will last, and hence, it is still a mystery if the vaccines will provide life-long immunity.

Other human Corona viruses give us a clue about how long the targeted antibodies last in the human body. Four types of Corona viruses that cause the common cold produce immunity that is short-lived, lasting for less than a year. However, once infected, COVID-19 re-infection is generally milder, which is also expected with COVID-19.

Have people caught COVID-19 twice?

Until recently, many cases of re-infection with COVID-19 have been reported. However, these were considered as errors with people wrongly being told they were free of the virus after infection. In other words, a relapse of the disease was mistaken as re-infection.

A 33-year-old man from HongKong was infected with Coronavirus for the second time after four months. This was the first proved case of a re-infection by Coronavirus, as Genome Sequencing confirmed that the two virus strains were different. However, the patient showed no symptoms after re-infection. This makes it a textbook case demonstrating that infection by virus produces immunity against the disease on re-infection. This means that the body had produced antibodies against the virus the first time he was infected. These antibodies prevented the appearance of any symptoms of re-infection by Corona virus.

This demonstrates that the antibodies provide protection from COVID-19, but may not prevent getting infected again and harbouring the virus in your system. This could mean that a person recovered from COVID-19, if re-infected, can still be a source of infection for those who are not protected from the virus.

Experts say that re-infection, though not impossible, is usually very rare. Also, one case cannot be considered a conclusive study. Limited experiments done on Rhesus monkeys show that when re-infected with Coronavirus causing COVID-19 after three weeks, they did not develop any symptoms. However, it is yet to be found out how long immunity against Coronavirus lasts and whether it prevents re-infection.

Do antibodies against Coronavirus make me immune?

The presence of antibodies does not guarantee immunity. It has also been seen that the levels of antibodies vary depending on the severity of the symptoms developed. This can especially be problematic when immunity passports are considered a way out of the pandemic.

If there are antibodies in a person’s system, they are assumed to be eligible to go back to work. This was particularly considered for frontline workers in the health sector who have a high risk of exposure to Coronavirus.

While every patient who is infected by COVID-19 develops antibodies, the levels are not the same. Studies have shown up to 30% of the patients who have been infected with COVID-19 show very low levels of neutralizing antibodies (antibodies that attach to Coronavirus and stop them from infecting other cells). Also, being immune to the virus does not mean you cannot harbor the virus and spread it to vulnerable groups of the society.

-Apurva

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