Countries all over the world have been fighting against the novel coronavirus using preventive measures such as social distancing and lockdowns. After India being in lockdown for almost half a year, certain relaxations have gradually been implemented to resume economic activities.
Amidst the rising number of new cases daily, the first documented case of reinfection with Covid-19 was reported in a 33-year-old man in Hong Kong almost 4 ½ months after he recovered from his first infection. Closer to home, recently there have been reports of reinfection cases in Bangalore, Delhi and Mumbai, especially amongst healthcare workers. Researchers in India have also reported few cases with asymptomatic reinfection of Covid-19.
What is COVID-19 reinfection?
In simple words, reinfection means that a person was infected once, cleared the infection and then the person was infected again.
Initial evidence suggests that normally, in case of an infection, the COVID Immunoglobulin G (IgG) antibody is tested positive after 2-3 weeks of the infection. However, in certain cases, the antibody tests negative, which means that the person does not develop immunity after infection. Another possibility could be that the antibodies are short-lived and disappear quickly, thereby making the patient susceptible to reinfection. Thus, reinfection cases mean that the antibodies may not be produced by every patient or if they do develop, they may not last long enough, and therefore, allowing the virus to enter the body and cause the disease again.
The World Health Organisation (WHO) has stated that there is currently no evidence that people, who have recovered from COVID-19 and have antibodies, are protected from a second infection.
What are the symptoms of reinfection?
Though the patient from Hong Kong experienced a cough, sore throat, fever and headache during his first infection, he was asymptomatic during his second infection. On the contrary, a 25-year-old man in the US developed breathing difficulties and pneumonia after getting re-infected with COVID-19, despite having only mild symptoms during his first infection.
How is reinfection established?
Although there could be a chance that the virus was quite low enough to go undetected and appear negative on a test, only to increase and be picked up in the next test, the question arises as to whether the same virus has resurfaced again or is the current infection caused due to another viral event.
Determining reinfection is quite a challenging process. Genetic material gathered from the first and second swabs of the patient must be analyzed and sequenced by using genetic engineering. If there are differences that show up during sequencing, it means that reinfection has occurred. If the sequences match, then it means that there could be a relapse.
As of now, health officials in India are of the opinion that reinfection with COVID-19 is very rare. Observations till date have shown that only mild infections have occurred and therefore this issue is not of serious concern now.
How could this impact a vaccine?
As per early-stage reports from vaccine clinical trials being conducted worldwide, the vaccine produces less immunity than an infection. There is still a lot of testing and data that is required in order to ascertain the level of immunity that the vaccine would provide. However, we may require booster doses in order to maintain immunity and avoid infection.
How will this affect herd immunity?
Herd immunity is based on the principle that a disease can be eradicated if most of the population is immune to it. With cases of reinfection being reported and confirmed, researchers are increasingly sceptical about achieving herd immunity since it may be impossible to achieve. Once again, more research is needed in order to confirm this fact.
What should I do once I have recovered from Covid-19?
Recovery from COVID-19 does not mean that you are immune to the disease. You should avoid getting complacent and continue maintaining hand hygiene, wearing masks and ensuring social distancing even after recovery.
Since COVID-19 is a relatively new disease, there is not much data available in order to understand the kind of long-term immunity that patients develop after they have recovered from the infection.
With respect to the novel coronavirus and COVID-19, a lot is still left to be learned. Research is still underway in order to understand various aspects of the disease and its threat of reinfection as well as the vaccine and immunity. In all cases, health officials have advised that the chances of reinfection are rare and not a cause of serious concern.