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The reinfection cases have raised concerns about people’s immunity to coronavirus as the world struggles to tame the pandemic.
The cases have also raised concerns about the efficacy of potential vaccines against the virus, which has killed hundreds of thousands of people, although experts say many more cases of reinfection would be needed to justify them.
Is reinfection possible?
Scientists still don’t know for sure, but they think it’s unlikely.
Although few cases of reinfection have been reported in recent days, scientists in India and elsewhere said that there is still no cause for alarm and that more studies are needed for a reliable inference.
No broad conclusions can be drawn about the reinfection of individual cases, noted Belgian virologist Marc Van Ranst. “Since we do not yet know how frequent reinfections are, it is difficult to say what these findings mean for the success of a vaccination campaign,” said Ranst, a clinical biologist at the UZ Leuven academic hospital in Belgium, addressing concerns that the reinfection could also impact the vaccination program.
Immunologist Satyajit Rath stated that no conclusions can be drawn about the functioning of the immune system against the virus from case studies of individual patients. “We don’t know anything about immunity and reinfection interactions in these patients. Especially since so far there seem to be only three confirmed cases,” said Rath, from the National Institute of Immunology in New Delhi.
Ram Vishwakarma, former director of the Indian Institute of Integrative Medicine in Jammu, explained that the human immune system is too complex to make comprehensive statements about reinfection from studies of individual patients.
According to some experts, reinfections are rare but possible. “We already knew this, because immunity is never 100%,” said Kristian Anderson, professor of immunology and microbiology at Scripps Research in La Jolla, California.
The researchers have emphasized that reinfection with the virus is likely rare, but said recent findings imply that initial exposure to the virus may not result in full immunity for everyone.
Why is the Nevada case complicated?
The 25-year-old Reno man with mild COVID-19 symptoms was found to initially have the virus in April, recovered and tested negative twice, and then tested positive again in June.
But he was much sicker the second time, with pneumonia that required hospitalization and oxygen treatment.
Researchers from the University of Nevada, Reno School of Medicine, and the Nevada State Public Health Laboratory said they were able to demonstrate through sophisticated testing that the virus associated with each instance of the Reno Man infection represented genetically different strains. .
Similar but different virus
Genetic testing for each episode showed that the viruses were similar in important ways, but differed by at least 12 points, which would be highly unlikely from the natural history of the bug if man had it continuously rather than getting infected a second time, said Mark Pandori, director. from the Nevada State Public Health Laboratory.
The case “should cement in our minds that there is no such thing … as invulnerability” to the virus, even if you’ve already had it, Pandori said. “You can get sick again and that disease can be quite serious.”
Do people develop immunity after being infected?
There is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection, according to the WHO. Developing immunity to a pathogen through natural infection is a multi-step process.
According to the WHO, some governments have suggested that the detection of antibodies against SARS-CoV-2, the virus that causes Covid-19, could serve as the basis for an “immunity passport” or “risk-free certificate” to allow that people travel or return to work assuming they are protected against reinfection.
There is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection.
WHO spokeswoman Margaret Harris told a UN briefing in Geneva on the Hong Kong case that while there were anecdotal reports of reinfections, it was important to have clear documentation.
Why does reinfection occur?
Even though there is little clinical evidence on people getting Covid-19 again, scientists suggest that there may be multiple meanings for what reinfection could mean, making us understand why this could happen.
A likely reason for this could be the fact that once a person recovers from the infection, the viral load in the body is depleted. In some cases, a recovered patient could continue to have low levels of the virus in the body, thus making them prone to showing symptoms and reinfection.
Viral load may persist in the body for up to three months, which is the time that most people who are reinfected are diagnosed. However, scientists believe that a positive diagnosis a second time, after full recovery, is not a case of reinfection, but spread of the virus due to the virus remnants left in the body.
What does reinfection mean for immunity?
Hong Kong’s reinfection case offers some reassurance about immunity. Although the Covid-positive man had Covid again just four months after the first bout, the second round was asymptomatic, which one expert said is the “textbook example of how immunity should work.”
These first confirmed cases of reinfection suggest that the new coronavirus could more closely resemble common cold viruses, which can cause repeat infections within months, rather than SARS or MERS, which generally produce immunity for a few years.
But it is not clear how severe reinfections can be for other people and whether immunity after an infection is expected to last only a few months for most people. Even being asymptomatic after reinfection poses a risk for other reinfections, however, do not rule out herd immunity as a broader defense mechanism until a vaccine is developed.
The role of the vaccine
Cases of reinfection can raise questions about the efficacy of vaccines, but experts say that reinfection is an important reason to get vaccinated, since vaccines can produce better immunity than disease.
Kelvin Kai-Wang To, one of the researchers on the Hong Kong study, told Fortune magazine that “it is likely that vaccination can induce stronger and longer-lasting immunity than natural infection.”
The researchers said that SARSCoV-2 “can persist” like other common cold coronaviruses, even for those that acquire immunity through natural infection or vaccination. In that case, you may require regular booster injections for immunity against evolving strains of the virus, such as the flu.
Even if a vaccine isn’t effective in perpetuity, it’s worth getting vaccinated, experts say, noting that an early brush with the virus, through infection or vaccination, can lead to milder illness the next time, as the immune system may be better equipped to cope.
Reinfection Cases from India
In India, Telangana and Gujarat have reported what could be the country’s first documented reinfections.
Last week, Telangana said it has two cases of Covid-19 reinfection among front-line medical professionals and is investigating whether two different strains of the new coronavirus were responsible.
Reinfection was reported with a difference of one and a half to two months in both cases.
“Although they had undergone RT-PCR tests both times and had tested positive, they were initially completely asymptomatic. There is a possibility that they will become re-infected after being exposed to a different strain of the virus, ”said Dr. G Srinivasa Rao, director (public health) of Telangana.
No need to be alarmed: ICMR
The main health research body, ICMR, said on Tuesday that there is “no need to be greatly alarmed” by the case of Covid-19 reinfection reported in Hong Kong, but at the same time maintained that it is not yet known how long the immunity. lasts in case of coronavirus.
At a press conference, the Director General of the Indian Medical Research Council, Balram Bhargava, said that the Hong Kong case is a lost example and that reinfection may depend on several factors.
Citing the example of measles, he said that once it affects, it gives immunity for life. But you can rarely get measles a second time.
(With inputs from agencies)
