Bengaluru: People who have recovered from Covid-19 may have antibodies only for two to three months, said a study published Thursday in Nature Medicine.
However, the conclusions might not necessarily mean that a recovered person can get reinfected, stated the authors.
The limited findings offer clues to one of the biggest questions about Covid recovery, vaccination, and serological surveys.
The study is the first to determine the existence of antibodies in asymptomatic patients and characterise them. Previous studies have shown that infected patients who display symptoms do develop antibodies as well, but it remained unclear how long these lasted.
Another paper published in Nature Medicine, also released Thursday, found that even small amounts of antibodies could work to protect against the virus.
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Asymptomatic vs symptomatic
The new study compared 37 asymptomatic patients with 37 symptomatic patients who had all been quarantined after testing positive in the Wanzhou People’s Hospital in China.
The authors found that the immune response in asymptomatic people was weaker as compared to those who showed symptoms. They also found that antibody levels started falling much faster in asymptomatic patients than in symptomatic ones.
Antibodies reduced in 40 per cent of the asymptomatic group as compared to 12.9 per cent in the symptomatic group during the early convalescent or recovery stage — about eight weeks after individuals were discharged from the hospital.
IgM, the antibodies produced during the preliminary stages of the infection, were found to last longer in symptomatic patients. When tested for IgM antibodies three to four weeks after falling sick, it was found in 78.4 per cent of the symptomatic people and 62.2 per cent of the asymptomatic group.
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Body response during the infection
During the acute phase of the coronavirus infection, which is defined as when nasal swabs test positive for the virus, asymptomatic patients displayed lower levels of IgG antibodies, those produced in the later stages of the infection that help carry an individual to recovery.
However, during the early convalescent phase, the IgG count dropped in 93.3 per cent of asymptomatic individuals, lower that the 96.8 per cent of the symptomatic group.
Neutralising antibodies, which deactivate the spike protein the coronavirus uses to gain entry into cells, decreased in 81.1 per cent in the asymptomatic group and in 62.2 per cent in the symptomatic during recovery.
Asymptomatic people also displayed lower levels of pro- and anti- inflammatory cytokines, which are proteins responsible for transmitting signals between immune system cells. Cytokine levels found in asymptomatic individuals were comparable to completely healthy individuals.
Antibodies to other coronaviruses such as SARS and MERS are thought to last at least a year. Some SARS antibodies in individuals have lasted for two years, while some MERS antibodies have been detected 34 months after recovering from the infection.
Also read: Are people who have had Covid-19 immune? Perhaps not
Shedding factor
The study also found that asymptomatic people were shedding the virus, i.e., releasing a replicated virus to the environment, for far longer than symptomatic people did.
Symptomatic people shed the virus for 14 days while asymptomatic people did so for 19. However, it is unclear if the virus being shed at later stages is capable of infecting others or is just viral RNA remnants.
Viral shedding data also varies across studies; previous studies have shown viral shedding occurring for up to 24 days after the onset of symptoms.
“Measurable virus shedding does not equate with viral infectivity, and further evaluation is needed,” wrote the authors of the paper.
The findings have implications for vaccine and serological surveys. The authors recommend that RT-PCR and serological testing should be used in conjunction to determine accurately the extent of asymptomatic transmission.
Also read: Israel develops key Covid antibody that ‘attacks and neutralises’ the virus in patient’s body
This is how background for vaccine will be made. Theres nothing like Covid antibody – the body has certain cells that detect foreign protein and work against it, it doesnt matter if they call it Covid or AIDS or Polio. A handful of people and their blind followers think and try to propagate this theory – one disease – one virus type – one set of symptoms – one particular type of antibodies- one medicine or one vaccine. If the ‘virus’ spreads the way they are saying, there is no way a human being can stop its spread – not by sitting at home, not by changing PPEs, not by washing hands, not by wearing any kind of face cover – and by this time the human race would have been extinct!! We can’t even stop dust particles from entering our house and from falling on our body, which are 1000 times larger than an RNA – no matter, however closed a room is, however packed a pack/carton is – its a fallacy which the entire human race is being put through for the past 6 months. Life thrives on the planet, not because everybody is careful, but only because life knows to adapt itself to changing scenarios. By the way, if the new RNA had come from a ‘bat’ in Wuhan, did anybody think, why no other bats in the entire world could ‘spread’ a single such virus again after the Wuhan fish/animal market incident? These are the stories they tell us to sell fear and then its remedy, this has been happening for over a century and more so in the past 60 years. Everybody must be remembering about the Zika virus story of Brazil – the malformed human babies born were attributed to a non existent exogenous RNA (they called it Zika, just like Covid), while the malformation was due to a chemical pesticide that contaminated the food and water in a particular area of Brazil – and how can we forget the great Ebola which they have been trying to export to the rest of the world, fortunately the rest of the world doesnt use the same killer chemical that caused Ebola in Africa – so they are not able to export “Ebola virus”. we can hear another ‘virus’ outbreak in the next 3-4 years due to Glyphosate which is another disaster in waiting – lets all try to hunt for a nice name for a new RNA by then , the poor WHO would need a new name for it.
Omg let the real experts worry abt this pandemic everyone has diffrent opinions diffrent ways of looking at everything. Just pray for the best and for the scientists experts and doctors can find a real cure so we all can be good stay safe and be positive
Could you kindly post original references here
Thanks
This is 100% nonsense. At no time in the last 30 years has any SARS virus not left permanent antibody immunity after being infected. Symptomatic or Asymptomatic.
To even suggest that people only have temporary immunity is ludicrous and flies in the face of established virology. SARS-COV-2 is not some amazingly new and different pathogen – it’s just another SARS coronavirus. That’s why it was given the designation SARS-COV-2; it’s a variation of SARS-COV-1.
How can we come to know,which country has found antidote,in news Israel has found….
Obviously, they had enough antibodies to fight it off the first time..and perhaps their bodies have learned to manufacture them when needed…. not sure they would always be present..just a guess..does this mean a vaccine won’t work???
So complex technology of this intruder , capable to transform other cells in our body. Body should defend ( prevent) or destroy ( cure) this intruder.
Ive had covid. Id be will to try to get reinfected. I dont believe i will get it again… ive been donatingvthe antibodies. 12 sessions now and still going. I was diagnosed april 7.
Perhaps & maybe are terms that are not scientific & seem to be promoting a narrative rather than being good science forward
What narrative?
The words perhaps and maybe were not even used in the article. What is wrong with you?
If you ask me, you seem to have an agenda to criticize simply for the sake of it.
Don’t understand why are we bombarded by half baked inconclusive reseaches right from the start of this pandemic like virus can last for 3 days on some surfaces (no one talked about study was done indoor at 20 centigrade temperature), virus can travel upto 29 feet and now this
Because some information is better than no information.
The researchers were generally candid and said they were only preliminary results.
It takes time for good quality science. But we still need something to go by until then.
Observation is right to the best of my knowledge as studied in Microbiology. Antibodies reduce and even disappear over time. Immunity or the memory to produce antibodies is in B cells. So reduction in number of antibodies in either of the cases is natural.
Study provides no definite answer to following vital points –
a. No definitive answer to whether recovered individual may get re-infected or not
b. Asymptomatic individuals shed the virus; but no definitive answer for infectivity
Though i admire science writing, i am unsure of it’s importance for audience “The Print” has. I believe, The Print does not position itself to cater to audience with advanced knowledge on Science, but a rather broad set of people.
This is so anti science it hurts… That is not how the body works…. Quit pushing your stupid agenda….
What agenda? What anti-science?
When you make accusations, explain. No one can read your imagination.
How exactly do you think that body works?