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People who have recovered from Covid-19 will develop an immune response that will protect them, but it's not clear how long it will last for, a leading UK virologist says.
Photo: AFP
The World Health Organisation last month published a tweet saying there was no evidence people who had Covid-19 and had antibodies were protected from a second infection.
It later issued a correction, noting its tweet had "caused some concern".
"We expect that most people who are infected with #COVID19 will develop an antibody response that will provide some level of protection," it clarified.
Leading UK virologist Chris Smith told Kim Hill on Saturday Morning what WHO meant to say was it doesn't know if people develop long-term immunity to Covid-19, and it had acknowledged its mistake.
There were also reports last month about South Korean health officials investigating how more than 200 people who had recovered from Covid-19 had tested positive again. It was feared they had been reinfected, but Dr Smith said the country had now admitted it got it wrong.
South Korea’s infectious disease experts said on Thursday that dead virus fragments were the likely cause of false-positive results, and there was little evidence to believe the cases were reinfections or reactivations, according to The Korea Herald.
Dr Smith said people who had Covid-19 would develop antibodies that were underpinned by memory cells, which would persist "for a really long time".
So humans would get an immune response which protected them, but it's not clear how long it would last.
"And the reason we can't say that is because we've only known about the virus for five months. So we've only been studying people for five or six months," Dr Smith said.
"So we're not going to know yet if you get five years, 50 years, the rest of your life immunity, or just five months? We don't know yet, but it's likely we're going to get some degree of sustained immune response which makes the prospect of getting a vaccine that's going to work that bit more likely, which is very reassuring."
Covid-19 no 'one trick pony'
The loss of one's sense of smell was now officially a symptom of Covid-19, and there's a good biochemical reason to explain that, Dr Smith said.
The virus clings on to cells which give your sense of smell and taste, and the cells ooze out a protein cutting enzyme protease.
"And this is a useful component to have sitting there because when the virus comes along that protease goes snip, and it cuts a very specific part of the protein on the surface of the virus, disclosing the active part of the receptor. It's almost like pulling the pin on the hand grenade."
Most people who recovered from Covid-19 regained their sense of taste and smell a week or two later.
While fever was initially believed to be the number one symptom of the virus, the repertoire of symptoms was now much broader than first thought, and in many cases people with Covid-19 didn't have a fever.
Symptoms included fever, loss of sense of taste and smell, headache, fatigue, nausea, diarrhoea and vomiting.
"So those other things, also, we're now realising are all part of the same symptom complex, and some people have some of them some have all of them.
"So this is the really interesting thing about this disease. It doesn't just present as one sort of one trick pony. It presents in many different ways. And that's probably why it makes people ill over such a broad spectrum from trivially ill to life threateningly ill, because it's producing such a range of different effects in different tissues at different times in different people in different ways."
Children with Covid-19 are infectious
Dr Smith said there was no reason to believe children with Covid-19 wouldn't spread the disease.
Director General of Health Ashley Bloomfield has previously said children had lower infection rates, were not as unwell if they did get the virus compared to other age groups, and did not tend to pass the virus on to adults.
But Dr Smith said children didn't go through "some bizarre metamorphosis to turn into an adult".
"So if you're a vulnerable adult, you're a vulnerable kid and vice versa, you might get slightly more severe symptoms, but you're still going to get infected. And if you've got symptoms, you're sure as hell gonna be infectious.
"And it's possible that you might have very mild symptoms, you're still potentially going to be infectious because you're growing the virus in the same way as an adult does. And therefore you're probably churning out the virus in the same way as an adult onto your airway surfaces and therefore you can spray that out, spit that out and spread it out over everybody else."