DURBAN – Why do some Covid-19 patients test positive weeks after the virus was first identified in their body? The answer is something Scientists are trying to figure out right now.
According to the World Health Organization (WHO), people who recover from Covid-19 develop antibodies in their blood. But some people appear to have low levels of neutralising antibodies.
So far, experts say these anecdotes don’t amount to definitive proof, but two recent studies – one from China and one from the United Kingdom found that the antibodies that fight against future infection faded within a few months.
The first study, from Wanzhou, China, and published in Nature Medicine, found that neutralizing antibodies faded quickly – after just eight weeks – in both asymptomatic and symptomatic people.
And a study published by King’s College in London, which has not yet been peer-reviewed, found that neutralizing antibody response may begin to decline just three to four weeks after Covid-19 symptoms initially emerge. The study also found a more durable antibody response in patients with more severe symptoms.
“It’s certainly not cause for alarm.We have anecdotes where the scientific basis is partial, but it’s not really tied up in a nice red bow. It’s not complete,” said infectious diseases specialist Dr. William Schaffner.
Inaccurate test results may also account for the phenomenon, says epidemiologist Michael LeVasseur.
“After you get sick, your immune system creates antibodies to fight future infection of a particular invader, like the novel coronavirus. In this case, people who contract Covid-19 produce antibodies that attack the virus to ward off future infections,” said LeVasseur.
Based on research from other coronaviruses, experts say there is a wide range in how long immunity lasts after an initial infection. For several of the common cold causing coronaviruses, prior infection might protect you for about six to 12 months.
Other types of coronavirus – such as the Middle Eastern Respiratory Syndrome, or MERS virus – may, however, result in several years of immunity. Given this variation, there is ongoing research to determine if the virus that causes Covid-19 will behave more like MERS or more like the common cold.
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