Covid-19 reinfection: Here’s all you need to know in 8 points

It has been almost 8 months that India is struggling with Covid-19 pandemic. With over 50 lakh cases and 80,000 deaths, the pathogen spread is yet to be brought under control. Besides daily record infections of 95,000 or above, another concern has emerged which is reinfection.

The discussions about Covid-19’s reinfection are on at the national and global level as patients getting contracted the virus for second time are coming to the fore across the globe. Though the numbers are not alarmingly high yet, still the cases are emerging in many countries. In this article, we shall discuss all the aspects related to Covid-19 reinfection, cases, scientists’ take on the matter, why you shouldn’t worry about it and many more.

Covid-19 reinfection: Here’s all you need to know in 8 points

1. The first known case of reinfection

The case of a Hong Kong man is known worldwide for one of the first Covid-19 reinfection cases. The patient who recovered more than four months ago has reportedly been reinfected with SARS-CoV-2, the virus that causes Covid-19. But during the second time, he didn’t have any symptoms. Scientists in a report say that this is not necessarily unexpected, because very few natural infections generate an immune response that completely prevents reinfection. Instead, what generally happens after an infection is that the body’s immune response gradually declines over months after the infection is cleared.

Specialised immune cells in the body are tasked with remembering each particular infection, so if you get infected again your body quickly starts producing the relevant antibodies and other immune cells (called T cells) in large numbers. This helps clear the new infection more rapidly and effectively. So you can still get reinfected, but you’re more likely to have fewer symptoms or be asymptomatic. This is what seems to have happened to the 33-year-old Hong Kong man at the centre of the latest reports. The first infection caused symptoms, which he reportedly suffered from for some time. But the second time around he was asymptomatic, presumably because his body effectively repelled the disease.

2. A similar phenomenon was located among monkeys

The same phenomenon has previously been shown in monkeys, with one experimental study showing reinfection with SARS-CoV-2 is possible, but that reinfection did not result in the development of disease, says an analysis. As experts, we have to be careful about over-interpreting what we know about this case. This is just one person. Is he the exception or the rule? We are yet to know for sure and are waiting for further research.

3. What is the effect of reinfection on our immune system?

There is good news in this case. This particular person’s immune system seems to have recognised the second infection, as shown by the fact his blood boosted antibodies against it. Despite the mutation, the man could still mount a good defence against the new strain. “Antibodies usually last in the blood for roughly 120 days following a stimulus such as natural infection with a virus or injection with a vaccine, though it varies depending on the disease. Both the B cells that produce antibodies, and the T cells that kill infected cells, also wane over time after the stimulus,” describes a report.

Now if we talk about the support of vaccines, they can induce longer-lasting responses. But the key point is both natural infections and vaccines do generate memory B and T cells. So when the body comes in contact with the infection for the second time, the memory cells respond rapidly and in high numbers. This can be so quick and strong that in some cases it can even result in sterile protection, effectively preventing the virus from infecting our cells. As experts assume that there may be a small lag time for the immune system to respond fully, but in the end, the virus is still unlikely to infect many cells.

4. Can we pass the virus on if reinfected?

As per the latest development, at the moment it’s unclear if asymptomatic carriers can transmit infection. Indeed, there may be different types of asymptomatic carriers. Some asymptomatic people might transmit the virus, while others don’t. We don’t know why this is the case. But as per scientists’ experience with other diseases, the higher the number of viral particles being spread from person to person, the higher the chance of infection. Therefore, asymptomatic carriers, who do not shed lots of virus through coughing or sneezing, should in theory have a lower risk of infecting others.

5. Is reinfection related to herd immunity?

As researchers believe that herd immunity is still possible if we get a successful vaccine, because vaccines can be more powerful and protective than the immunity conferred by being naturally infected with the virus. Some epidemiologists suggest at least 70% of a population needs to be immunised to achieve herd immunity.

What’s more, becoming reinfected does not mean the virus will necessarily be transmitted — it depends on the viral dose and the susceptibility of people around the infected person. If we are all immunized with a vaccine, we generate a ring of fire that can contain the spread of the virus. It’s also possible SARS-CoV-2 becomes an endemic virus, like many viruses circulating in the population. But as long as there are diagnostics, vaccines and treatments, we could continue functioning normally just as we do with influenza present in the population. Ultimately it’s about what level of risk society is willing to accept. And we may need to use infection control methods like masks and hand hygiene for some time.

6. What do experts feel about reinfection cases in India?

The Indian Council of Medical Research recently stated that coronavirus reinfection is possible, but it is a “very rare” occurrence, PTI reported. ICMR director general Balram Bhargava said this as suspected cases of reinfection being reported from abroad and from Telangana, Karnataka, Gujarat, Punjab and Maharashtra.

“We have seen that someone gets measles and he is supposed to be protected all his life because he generates certain antibodies, but then we have seen reinfection occurring in measles. Similarly, we can have reinfection with COVID-19 as has been described by the case in Hong Kong and it is not a matter of serious concern,” Bhargava told a press conference.

7. How does one person gets infected twice?

As experts explain in such cases of a person testing positive in a second instance, it could be that what you may be detecting (in the test) is not a viable virus but viral nucleic acid. The RT-PCR test (the reverse transcription-polymerase chain reaction test used to confirm a Covid-19 infection) doesn’t allow you to distinguish whether your sample contains a viable virus which is capable of infecting others or it simply contains fragments of viral genetic material without a viable virus. It could be a case that it is simply genomic fragments. But this is a big relief to know that even as the Covid-19 caseload worldwide has crossed 27 million, cases of reinfection are extremely rare.

8. What is the Centre saying about reinfections in India?

The government admitted that reinfections were happening but reiterated that they were “very, very rare”. This is the first time that the government had acknowledged that reinfections were taking place. A few weeks ago, Health Secretary Rajesh Bhushan had dismissed “hypothetical” questions about a health ministry staffer getting reinfected with Covid-19. Studies have shown that the level of Covid-19 antibodies declines after two-three months of recovery. However, immunologists pointed out that antibodies are not the only thing protecting our bodies from reinfections. So the risk factor or concern is less in such cases.

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